Journal of Traumatic Stress June 2014, 27, 323–330
Posttraumatic Stress Disorder in a Nationally Representative Mexican Community Sample Guilherme Borges,1,3 Corina Benjet,1 Maria Petukhova,2 and Maria Elena Medina-Mora1 1
Direcci´on de Investigaciones Epidemiol´ogicas y Psicosociales, Instituto Nacional de Psiquiatr´ıa Ram´on de La Fuente Mu˜niz, Mexico City, Mexico 2 Department of Health Care Policy, Harvard Medical School, Boston, Massachusetts, USA 3 Universidad Aut´onoma Metropolitana, Mexico City, Mexico
This study describes the public health burden of trauma exposure and posttraumatic stress disorder (PTSD) in relation to the full range of traumatic events to identify the conditional risk of PTSD from each traumatic event experienced in the Mexican population and other risk factors. The representative sample comprised a subsample (N = 2,362) of the urban participants of the Mexican National Comorbidity Survey (2001−2002). We used the World Health Organization’s Composite International Diagnostic Interview (CIDI) to assess exposure to trauma and the presence of PTSD according to the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association, 1994) in each respondents’ self-reported worst traumatic event, as well as a randomly selected lifetime trauma. The results showed that traumatic events were extremely common in Mexico (68.8%). The estimate of lifetime PTSD in the whole population was 1.5%; among only those with a traumatic event it was 2.1%. The 12-month prevalence of PTSD in the whole population was 0.6%; among only those with a traumatic event it was 0.8%. Violence-related events were responsible for a large share of PTSD. Sexual violence, in particular, was one of the greatest risks for developing PTSD. These findings support the idea that trauma in Mexico should be considered a public health concern.
Traumatic events such as interpersonal violence as well as natural and manmade disasters are common risk factors in Mexico among the adult (Baker et al., 2005; Medina-Mora, Borges, Lara, Ramos-Lira, et al., 2005; Norris et al., 2003) and adolescent populations (Benjet et al., 2009; Orozco, Borges, Benjet, Medina-Mora, & L´opez-Carrillo, 2008). As expected, these events increase the risk of developing mental disorders (Benjet, Borges, M´endez, Fleiz, & Medina-Mora, 2011) and suicidality in the Mexican population (Borges et al., 2008) as they do elsewhere (Stein et al., 2010). A matter of concern is the impact of traumatic events on the development of posttraumatic stress disorder (PTSD) in Mexico. Two prior efforts in the country delved into these issues (Medina-Mora, Borges, Lara, Ramos-Lira, et al., 2005; Norris et al., 2003), but they did not present the complete spectrum of traumatic events in Mexico, and did not account for multiple traumatic events, estimating the impact of single events only on the population impact of PTSD. Because experiencing multiple traumatic events is a common situation, this was an important limitation of these studies. One of these prior reports also acknowledged that PTSD was assessed only among respondents who considered the particular event to have been their worst experience. The lack of inclusion of a randomly selected traumatic event, as well as one of the worst events, was mentioned as a limitation in this prior study in Mexico (Norris et al., 2003).
Research conducted by Guilherme Borges, Direcci´on de Investigaciones Epidemiol´ogicas y Psicosociales, Instituto Nacional de Psiquiatr´ıa Ram´on de la Fuente Mu˜n´ız. The Mexican National Comorbidity Survey is supported by The National Institute of Psychiatry Ramon de la Fuente (INPRFM-DIES 4280) and by the National Council on Science and Technology (CONACyTG30544-H), with supplemental support from the Pan American Health Organization (PAHO). The Mexican National Comorbidity Survey is carried out in conjunction with the World Health Organization World Mental Health (WMH) Survey Initiative (WMH) Survey Initiative, which is supported by the National Institute of Mental Health (NIMH; R01 MH070884 and R01 MH093612-01), the John D. and Catherine T. MacArthur Foundation, the Pfizer Foundation, the U.S. Public Health Service (R13-MH066849, R01MH069864, and R01 DA016558), the Fogarty International Center (FIRCA R03-TW006481), the Pan American Health Organization, Eli Lilly and Company, Ortho-McNeil Pharmaceutical, GlaxoSmithKline, and Bristol-Myers Squibb. We thank the staff of the WMH Data Collection and Data Analysis Coordination Centers for assistance with instrumentation, fieldwork, and consultation on data analysis. None of the funders had any role in the design, analysis, interpretation of results, or preparation of this article. A complete list of all within-country and cross-national WMH publications can be found at http://www.hcp.med.harvard.edu/wmh/. Correspondence concerning this article should be addressed to Guilherme Borges, Direcci´on de Investigaciones Epidemiol´ogicas y Psicosociales, Instituto Nacional de Psiquiatr´ıa Ram´on de la Fuente Mu˜n´ız, Mexico, Calzada M´exico Xochimilco No 101-Col. San Lorenzo Huipulco, M´exico D.F., C.P.14370 M´exico. E-mail: [email protected] or [email protected] C 2014 International Society for Traumatic Stress Studies. View Copyright this article online at wileyonlinelibrary.com DOI: 10.1002/jts.21917
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The main problem with estimates based on the worst-event approach is that the estimates of conditional risk for PTSD tend to be overestimated when compared to an estimate that also uses a random sample of all events, because worst events are not necessarily representative (Atwoli et al., 2013; Stein et al., 2012). The Mexican National Comorbidity Survey (MNCS) allowed for the first time to combine both approaches to estimate the risk of PTSD by assessing (a) PTSD associated with the worst trauma and (b) one additional trauma selected at random from all the lifetime traumas reported by each respondent. Also, when correctly weighted, these responses may be used to estimate the population prevalence and distribution of lifetime PTSD associated with the wide range of traumas assessed in the MNCS. The goals of this study were to describe the public health impact of trauma exposure and of PTSD in relation to the full range of traumatic events, and to identify the conditional risk and risk factors of PTSD in relation to each type of traumatic event experienced in the Mexican population.
Method Participants and Procedure The MNCS is part of the World Health Organization’s World Mental Health Survey Initiative (Demyttenaere et al., 2004). The survey was based on a stratified, multistage area probability sample of noninstitutionalized persons aged 18 to 65 years living in urban areas (population 2,500+) of Mexico. About 75% of the Mexican population is urban and meets the above definition. Data collection took place from September 2001 through May 2002. The response rate was 76.6% for a total 5,782 respondents. All respondents were administered a Part I interview; to decrease the burden of a long interview process, only a selected subsample of 2,362 received a Part II interview. The Part II interview included questions on supplemental psychiatric disorders and traumatic events, and thus are the study participants. The sample receiving Part II consisted of all respondents who screened positive for any disorder in Part I plus a subgroup of persons without symptoms. About one third of those who screened negative in the Part I interview were randomly assigned to the Part II interview. The subsample was then normalized, taking into account the probability of selection, to match the characteristics of the complete sample. There was a random selection process embedded into a computer algorithm for the selection of those screening negative in the first phase of the survey. All interviews were conducted at the respondents’ home after a careful description of the study goals was provided and informed consent was obtained. All recruitment and consent procedures were approved by the ethics committee of the National Institute of Psychiatry. Additional details of this study and sample have been published elsewhere (Medina-Mora, Borges, Lara, Benjet et al., 2005).
Measures Mental disorders including PTSD were defined by the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSMIV; American Psychiatric Association, 1994) and assessed with version 3.0 of the World Health Organization Composite International Diagnostic Interview (CIDI), a fully structured, computer assisted diagnostic interview administered face-to-face by trained lay interviewers. The World Health Organization translation protocol was used to translate the questionnaire (Kessler ¨ un, 2004; Robins et al., 1988). & Ust¨ The CIDI measures 29 different lifetime traumatic events and their ages of occurrence with questions such as “Were you ever involved in a very serious or life-threatening car accident?” Traumatic events were categorized into seven event classes as follows: war events, physical violence, sexual violence, accidents, death, and network events involving others. An additional question inquired about other traumatic events not included in the CIDI list. After the list of events was assessed, the respondent was asked if there was any other event that he or she suffered that had not been asked about in the prior list or which did not fit in any of the former categories. In this case, respondents were asked to give details about the event and this was recorded verbatim. Finally, the respondent was also able to select a private event category, which was reserved for traumas for which the respondent did not feel comfortable providing details or disclosing the nature of the trauma, also included in the Other category. Those who answered affirmatively on the occurrence of a lifetime event were also asked whether that event occurred within the last 12 months. Lifetime PTSD was assessed twice in the survey: once based on PTSD associated with the respondents’ self-reported worst lifetime trauma, and a second time based on one randomly selected trauma from all those reported by the respondent as ever having occurred to him or her. The randomly selected event was used to compensate for the fact that when PTSD rates are calculated using only the worst traumas that are atypical, the risk of PTSD may well be higher than for more typical traumas. Weights were applied to the randomly selected traumatic events to adjust for the fact that they represent only a sample of the respondent’s lifetime traumas. This produced a weighted dataset in which each trauma was represented in the proportion it occurred in the population. The remaining criteria for PTSD were assessed for each worst event and each random event. Criterion A2 was considered met if the respondent endorsed any of the three questions about whether at the time of the traumatic event, he or she felt terrified or very frightened, helpless, shocked, or horrified. The remaining criteria were then assessed whether or not A2 was endorsed with structured questions about reexperiencing (Criterion B), avoidance-numbing (Criterion C), arousal (Criterion D), duration (Criterion E), and clinically significant distress or impairment (Criterion F). A retrospective question also asked respondents for how many months or years symptoms continued. Responses to this question were used to define PTSD persistence. The 12-month prevalence of PTSD
Journal of Traumatic Stress DOI 10.1002/jts. Published on behalf of the International Society for Traumatic Stress Studies.
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was assessed among those with a 12-month event in a similar fashion. Data Analysis We used a design-based statistical analysis strategy for point and variance estimates and hypothesis testing, using standard survey data analysis procedures to account for design effects arising from the use of stratification, clustering, and unequal selection probabilities in the surveys and weights (Efron, 1988; Wolter, 1985). Based on respondents’ reports of their lifetime history of traumatic events, including the age at each event, we estimated the rates of trauma exposure using standard life table methods. We used a logistic regression model to study variation in the risk of first onset of PTSD by trauma types and sociodemographics, for both 12-month and lifetime PTSD (Hosmer & Lemeshow, 2000). Design-based standard errors for logistic regression coefficients and for pairwise contrasts between them were estimated using the Taylor linearization method with SUDAAN version 10.0141 (Research Triangle Institute, 2009) and were used in Wald tests for statistical significance and for producing 95% confidence intervals (CIs) for adjusted hazard ratios (Wolter, 1985). The first logistic regression model tested whether sociodemographics were associated with lifetime and 12-month PTSD in the population. The second model then evaluated the extent to which the coefficients in the first model changed with the focus only on respondents who were exposed to one or more traumas, adjusted for the classes of traumas implicated in the possible PTSD.
of developing PTSD following that event. In Table 2, we show that some events that have a high risk of PTSD are nevertheless rare and contribute little to the burden of PTSD, such as being a refugee, which was extremely rare (see Table 1). Thus, the class of events of physical violence (34.4%) and network events (20.9%) stand out as the main contributors to the burden of PTSD in Mexico. The two main events responsible for the largest burden of PTSD were having accidentally caused serious injury or death (13.7%) and having been sexually assaulted (13.6%). Finally, even when the symptoms associated with most events tended to be very persistent, there was a large variation in the duration of PTSD depending on the event. The variables associated with having lifetime PTSD in the total sample were being female (increasing the likelihood of PTSD by 4.8 times), and being both in the low-average and highaverage educational groups as they had lower odds ratios (ORs) for PTSD when compared to those in the high education group (Table 3). The analysis of lifetime PTSD among respondents with traumatic events, with type of event in the model, showed that none of the prior variables remained associated with PTSD except sex and being retired. A similar set of analyses were performed for 12-month PTSD (prevalence of 0.6%, 29 cases only, among the whole population and 0.8% among those with a traumatic event). The only variable that showed an association with 12-month PTSD was employment status; being unemployed, a student, or retired showed a very high likelihood of PTSD in comparison to being employed (OR = 6.56) in the total sample and among those with the traumatic events (OR = 9.81; full results not shown).
Results
Discussion
As shown in Table 1, 68.8% of the Mexican population suffered a trauma in their lifetime, with physical violence being the most common class (42.2% of the population and 28.5% as a percentage of all traumatic events), followed by network events (36.5% of the population and 24.5% as a percentage of all traumatic events). The single most common trauma was being mugged or threatened with a weapon (24.6%), followed by the unexpected death of loved one (22.7%). The lifetime prevalence of PTSD was 1.5% (68 cases) and among respondents with traumatic events the lifetime prevalence of PTSD was 2.1%. Table 2 presents the lifetime prevalence of PTSD by events and classes of events, as well as by percentage of all PTSD cases, and the duration of PTSD. Among event classes, other events had the highest risk of PTSD at 3.1%, followed by sexual violence, with a 2.6% prevalence of PTSD. For individual events, the highest risk of PTSD was associated with being a refugee (84.8%), accidentally caused serious injury or death (11.1%), those reporting a private event (4.2%), and sexual assault (3.8%). All other traumas had a lower comparative prevalence (0.0−3.2%). The burden of PTSD in the population is a joint function of the prevalence of the traumatic event and the conditional risk
The main findings of this research suggest that traumatic events are extremely common in urban Mexico (68.8%), but that lifetime PTSD is much less frequent (1.5%) in the whole population or among those with a traumatic event (2.1%). Despite some events significantly increasing the likelihood of subsequent PTSD (such as being a refugee in Mexico), they were so rare that their population burden was minimal. Other events, however, such as being sexually assaulted, stand out as particularly deleterious in Mexico due to the combination of a large likelihood of PTSD and a greater frequency of occurrence. Few demographic factors showed an association with PTSD, either lifetime or recent (12 month). Among them, being female and more educated had larger ORs for lifetime PTSD and being unemployed, a student, and retired had an increased likelihood of 12-month PTSD. Although the prevalence of PTSD was low, the duration of PTSD symptoms was particularly long, on average more than 5 years, but ranging from 4 months to 27 years depending on the type of event. The unusually long duration of PTSD in Mexico probably reflects the lack of service utilization in Mexico for this disorder, as well as long delays in seeking treatment. Prior research has suggested that 12-month service utilization in Mexico for mental health problems is 18.6% of those with
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Table 1 Prevalence of Traumas in the Mexican National Comorbidity Survey Event type No events War events Combat experience Relief worker in war zone Civilian in war zone Civilian in region of terror Refugee Injured, tortured, killed other Saw atrocities Accidents Toxic chemical exposure Automobile accident Other life threatening accident Natural disaster Man-made disaster Life-threatening illness Unexpected death of loved one Physical violence Kidnapped Beaten by caregiver Beaten by spouse or partner Beaten up by someone else Mugged, threat by weapon Sexual violence Raped Sexually assaulted Stalked Network events Child with serious illness Traumatic event to loved one Accidentally caused serious injury or death Saw death/dead body, or saw other seriously hurt Saw physical fight at home Others Some other event Private event Total with any event
Unweighted n
Weighted %
SE
% of all events
SE
17 0 1 2 5 2 2 5 428 27 132 37 104 20 108 273 572 19 194 98 53 208 134 36 71 27 430 67 32 6 146 179 60 12 48 1914
31.2 1.7 0.0 0.2 0.1 0.8 0.0 0.4 0.5 35.2 4.1 15.3 5.1 12.2 2.3 10.0 22.7 42.2 2.2 18.3 6.0 7.4 24.6 10.0 3.9 5.4 3.7 36.5 7.2 3.5 1.3 16.3 20.3 4.9 1.4 3.8 68.8
1.76 0.29 0.02 0.08 0.05 0.18 0.03 0.13 0.15 1.54 0.62 1.22 0.52 1.26 0.38 0.90 1.39 1.70 0.33 1.00 0.51 0.75 1.22 0.82 0.49 0.67 0.59 1.54 0.84 0.38 0.24 1.09 1.16 0.53 0.29 0.38 1.76
0.8 0.0 0.1 0.0 0.3 0.0 0.2 0.2 24.7 3.4 6.8 2.5 6.7 0.9 4.5 12.1 28.5 0.8 6.4 2.1 4.3 14.9 7.6 2.5 3.1 2.0 24.5 3.0 1.4 1.1 12.0 7.1 1.8 0.5 1.3 100
0.14 0.01 0.03 0.02 0.06 0.01 0.09 0.06 1.23 0.68 0.48 0.31 0.95 0.14 0.53 1.01 1.05 0.10 0.33 0.17 0.55 0.78 0.73 0.52 0.36 0.31 0.93 0.39 0.18 0.34 0.91 0.33 0.20 0.1 0.14 0.00
Note. N = 2,362. SE = standard error.
mental health needs (Borges et al., 2006), and although many people with lifetime disorders eventually made treatment contact, delays were long: 10 years for substance use disorders, 14 years for mood disorders, and 30 years for anxiety disorders (Borges, Wang, Medina-Mora, Lara, & Chiu, 2007). Treatment latency in Mexico is among the longest in a comparison of 15 countries around the world (Wang et al., 2007).Our group has reported previously on the prevalence of traumatic events and PTSD in Mexico (Medina-Mora, Borges, Lara, Ramos-Lira, et al., 2005; Medina-Mora, Borges, Benjet, Lara, & Berglund, 2007), whereas others (Norris et al., 2003) have reported es-
timates of PTSD for a smaller group of cities from Mexico and for a smaller set of negative life-events with estimations as high as 11.2%. Nevertheless, this is the first report of PTSD for Mexico that takes into account both the most severe (worst) and a random sample of all events. Thus, the estimates provided here of the impact of traumatic events on the occurrence of PTSD are more conservative. These estimates point to a low conditional risk for PTSD associated with most events in contrast to the previous study in Mexico. Research from a group of European countries (Darves-Bornoz et al., 2008) reported a 12-month prevalence of PTSD of 1.1%, higher than our
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Table 2 Prevalence of Lifetime PTSD by Events in the Mexican National Comorbidity Survey
na
Event type War events Combat experience Relief worker in war zone Civilian in war zone Civilian in region of terror Refugee Injured, tortured, killed other Saw atrocities Accidents Toxic chemical exposure Automobile accident Other life threatening accident Natural disaster Man-made disaster Life-threatening illness Unexpected death of loved one Physical violence Kidnapped Beaten by caregiver Beaten by spouse or romantic partner Beaten up by someone else Mugged, threat by weapon Sexual violence Raped Sexually assaulted Stalked Network events Child with serious illness Traumatic event to loved one Accidentally caused serious injury or death Saw death/dead body, or saw other seriously hurt Saw physical fight at home Others Some other event Private event Total with any event
1
1
7 4 3
9 23 3 5 9 2 4 17 6 9 2 5 2 1
2 9 1 8 71
PTSD episode (or residual symptoms in months)
Probability of PTSD (%)b
SE
% of all PTSD cases
SE
Mean duration
SE
1.1 – 0.0 0.0 0.0 84.8 0.0 0.0 0.3 0.0 0.9 0.0 0.3 0.0 0.0 0.3 1.0 3.2 1.5 3.1 0.2 0.7 2.6 1.2 3.8 2.3 0.7 0.7 0.0 11.1
1.05 – 0.00 0.00 0.00 18.20 0.00 0.00 0.16 0.00 0.56 0.00 0.18 0.00 0.00 0.13 0.29 2.51 0.82 1.45 0.14 0.39 1.18 0.61 1.67 2.30 0.61 0.62 0.00 11.10
1.0 – – – – 1.0 – – 9.5 – 7.4 – 2.1 – – 4.8 34.4 2.8 11.0 7.4 1.0 12.2 22.4 3.3 13.6 5.5 20.9 2.6 – 13.7
1.07 – – – – 1.07 – – 4.77 – 4.58 – 1.26 – – 1.99 9.10 2.29 5.21 3.56 0.67 6.39 8.31 2.02 5.88 5.01 15.01 2.17 – 8.61
324.0
0.0
324.0
0.0
37.1
6.2
41.4
7.5
22.2
11.0
16.6 79.7 4.8 112.8 145.1 6.7 33.3 125.1 164.3 161.6 11.5 12.0 9.8
4.7 29.0 2.0 59.0 60.0 2.0 19.0 40.0 48.0 59.0 0.7 16.0 2.4
4.0
0.0
0.0
0.00
–
–
0.6 3.1 0.6 4.2 0.9
0.45 1.34 0.65 1.95 0.39
4.7 6.9 0.3 6.5 100.0
36.5 32.8 60.0 31.0 67.9
27.0 19.0 0.0 20.0 40.0
3.55 3.44 0.14 3.42 0.00
Note. N = 2,362. PTSD = posttraumatic stress disorder; SE = standard error. a n is unweighted. b % is weighted.
estimate of 0.6%. The reason for the difference in prevalence of PTSD across countries or studies is poorly understood. Besides differences in the prevalence of events and their impact on PTSD, which seem mostly attributable to methodological differences in terms of the samples and types of events surveyed, all reports similarly point to the large role of violence-
related events as responsible for a large share of PTSD, and especially sexual violence as one of the most prevalent and with the greatest risk for developing PTSD. Methodological differences among studies, cultural differences in symptom presentation, and cultural differences with respect to factors contributing to risk and resilience following trauma
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Table 3 Demographic Correlates of Lifetime PTSD in the Mexican National Comorbidity Survey Predict LT PTSD among respondents with events, controlling for events
Total sample Variable
OR
Sex Male 1.00 Female 4.77 Age (years) 18−29 1.51 30−44 1.28 45−59 1.06 60+ 1.00 Marital status Married 1.00 Previously married 1.72 Never married 0.50 Education Low 0.64 Low-average 0.32 High-average 0.34 High 1.00 Employment status Working 1.00 Student 1.54 Homemaker 1.15 Retired 2.66 Other including unemployed 2.05 Type of random or worst event that was assessed for PTSD War events – Physical violence – Sexual violence – Accidents – Death – Network events – Other or private – Count of prior events Prior war events – Prior physical violence – Prior sexual violence – Prior accidents – Prior deaths – Prior network events – Prior other events –
95% CI
OR
95% CI
[1.0, 1.0] [1.25, 18.24]
1.00 4.51
[1.0, 1.0] [0.97, 20.77]
[0.41, 5.53] [0.55, 3.00] [0.29, 3.83] [1.0, 1.0]
3.68 2.21 2.01 1.00
[0.96, 14.03] [0.73, 6.70] [0.49, 8.11] [1.0, 1.0]
[1.0, 1.0] [0.65, 4.54] [0.22, 1.12]
1.00 1.49 0.85
[1.0, 1.0] [0.34, 6.47] [0.26, 2.77]
[0.22, 1.85] [0.10, 0.96] [0.15, 0.78] [1.0, 1.0]
1.11 0.32 0.50 1.00
[0.39, 3.12] [0.10, 1.01] [0.21, 1.20] [1.0, 1.0]
[1.0, 1.0] [0.30, 7.87] [0.40, 3.27] [0.38, 18.67] [0.45, 9.26]
1.00 1.81 2.11 11.52 5.90
[1.0, 1.0] [0.37, 8.88] [0.66, 6.73] [1.28, 103.31] [0.89, 38.91]
– – – – – – –
6.63 5.32 5.81 1.67 1.00 2.64 9.20
[0.61, 71.11] [1.67, 16.98] [1.29, 26.08] [0.44, 6.36] [1.0, 1.0] [0.49, 14.27] [2.26, 37.33]
– – – – – – –
1.16 1.31 0.96 1.14 1.02 0.95 0.70
[0.33, 3.70] [0.973,1.77] [0.69,1.33] [0.87, 1.51] [0.53, 1.97] [0.682, 1.33] [0.14, 3.58]
Note. N = 2,362. PTSD = posttraumatic stress disorder. LT PTSD = long-term posttraumatic stress disorder.
exposure could also explain some of the differences in the prevalence rates found here among studies. Familism, conceptualized as family cohesiveness combined with familial obligations, is a cultural trait often described in the Mexican population (Almeidia, Molnar, Kawachi, & Subramanian, 2009; Sabogal, Mar´ın, Otero-Sabogal, & Mar´ın, 1987). Although our current study
cannot address this hypothesis, the social support afforded by familism may play a protective role on the risk for developing PTSD following a traumatic event as it does for protecting against other negative health conditions in those of Mexican origin (Gallo, Penedo, Espinosa de los Monteros, & Arguelles, 2009; Germ´an, Gonzales, & Dumka, 2009).
Journal of Traumatic Stress DOI 10.1002/jts. Published on behalf of the International Society for Traumatic Stress Studies.
Posttraumatic Stress Disorder in Mexicans
Our results on the large and deleterious role of interpersonal violence and sexual events in Mexico are also in tandem with results on the impact of such events on suicidality (Borges et al., 2008) and on other mental disorders. The relatively low conditional probability of PTSD suggests that PTSD may not be the only or even the most common reaction to traumatic events. Although a good number of people may have sufficient coping resources to recover from trauma, research on the impact of trauma on other mental health conditions such as depression, anxiety, substance use disorders, and suicidality (Benjet et al., 2011; Borges et al., 2008; Stein et al., 2010) suggest that these may be alternative common responses to trauma (Borges et al., 2008). Our study is one of the first in the country that we are aware of to study factors associated with lifetime and 12-month PTSD in a sample of the general urban population. Being female was associated with lifetime PTSD, but not with 12-month PTSD. Prior epidemiological studies overwhelmingly report higher prevalence estimates for females than for males (Breslau & Anthony, 2007; Kessler, Sonnega, Bromet, Hughes, & Nelson, 1995; McLean, Asnaai, Litz, & Hoffman, 2011; Norris et al., 2003). These findings are largely consistent with basic research and animal studies that posit that a greater female vulnerability to traumatic events is due to differences in the stress response system at a biological level such as differences in corticotrophin-releasing factor functioning and the locus coeruleus-norepinephrine system, which contribute to increased stress sensitivity and hyperarousal in females (Bangasser & Valentino, 2012; Ressler et al., 2011). With regard to education and employment, lower educational levels and being employed were associated with lower lifetime and 12-month PTSD odds, respectively. The mechanisms that might account for this are still unclear. Our results should be framed in the context of the main limitations of this research. The information on lifetime events and dating of PTSD symptoms were obtained by self-report and may be subject to recall bias, forgetting, or willingness to report distressing traumatic events. Nevertheless, our survey estimates should be interpreted as lower estimates. It is more likely that these potential biases led to conservative estimates of the frequency of events and of the total prevalence of PTSD. This report used DSM-IV diagnostic criteria and because changes in the new DSM-5 only seem to slightly decrease the prevalence of PTSD (Kilpatrick et al., 2013) we believe that our current DSM-IV estimates can be used with confidence in Mexico, until new research with updated criteria are reported.
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Atwoli, L., Stein, D. J., Williams, D. R., McLaughlin, K. A., Petukhova, M., Kessler, R. C., & Koenen, K. C. (2013). Trauma and posttraumatic stress disorder in South Africa: Analysis from the South African Stress and Health Study. BMC Psychiatry, 13, 182. doi:10.1186/1471-244X-13-182 Baker, C. K., Norris, F. H., Diaz, D. M., Perilla, J. L., Murphy, A. D., & Hill, E. G. (2005). Violence and PTSD in Mexico: Gender and regional differences. Social Psychiatry and Psychiatric Epidemiology, 40, 519–528. doi:10.1007/s00127-005-0921-2 Bangasser, D. A., & Valentino, R. J. (2012). Sex differences in molecular and cellular substrates of stress. Cellular and Molecular Neurobiology, 32, 709–723. doi:10.1007/s10571-012-9824-4 Benjet, C., Borges, G., Medina-Mora, M. E., Zambrano, J., Cruz, C., & M´endez, E. (2009). Descriptive epidemiology of chronic childhood adversity in Mexican adolescents. Journal of Adolescent Health, 45, 483–489. doi:10.1016/j.jadohealth.2009.03.002 Benjet, C., Borges, G., M´endez, E., Fleiz, C., & Medina-Mora, M. E. (2011). The association of chronic adversity with psychiatric disorder and disorder severity in adolescents. European Child and Adolescent Psychiatry, 20, 459–468. doi:10.1007/s00787-011-0199-8 Borges, G., Benjet, C., Medina-Mora, M. E., Orozco, R., Molnar, B. E., & Nock, M. K. (2008). Traumatic events and suicide-related outcomes among Mexico City adolescents. Journal of Child Psychology and Psychiatry, 49, 654–666. doi:10.1111/j.1469-7610.2007.01868.x Borges, G., Medina-Mora, M. E., Wang, P., Lara, C., Berglund, P., & Walters, E. (2006). Treatment and adequacy of treatment of mental disorders among respondents to the Mexico National Comorbidity Survey. American Journal of Psychiatry, 163, 1371–1378. doi:10.1176/appi.ajp.163.8.1371 Borges, G., Wang, P. S., Medina-Mora, M. E., Lara, C., & Chiu, W. T. (2007). Delay of first treatment of mental and substance use disorders in Mexico. American Journal of Public Health, 97, 1638–1643. doi:10.2105/AJPH.2006.090985 Breslau, N., & Anthony, J. C. (2007). Gender differences in the sensitivity to posttraumatic stress disorder: An epidemiological study of urban young adults. Journal of Abnormal Psychology, 116, 607–611. doi:10.1037/0021843X.116.3.607 Darves-Bornoz, J. M., Alonso, J., de Girolamo, G., de Graaf, R., Haro, J. M., Kovess-Masfety, V., (2008) ESEMeD/MHEDEA 2000 Investigators. Main traumatic events in Europe: PTSD in the European study of the epidemiology of mental disorders survey. Journal of Traumatic Stress, 21, 455–462. doi:10.1002/jts.20357 Demyttenaere, K., Bruffaerts, R., Posada-Villa, J., Gasquet, I., Kovess, V., Lepine, J. P., . . . Chatterji, S. (2004). Prevalence, severity and unmet need for treatment of mental disorders in the World Health Organization World Mental Health Surveys. Journal of the American Medical Association, 291, 2581–2590. doi:10.1001/jama.291.21.2581 Efron, B. (1988). Logistic regression, survival analysis, and the KaplanMeier curve. Journal of the American Statistical Association, 83, 414–425. doi:10.1080/01621459.1988.10478612
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Kilpatrick, D. G., Resnick, H. S., Milanak, M., Miller M.W., Keyes, K., & Friedman, M. J. (2013). National estimates of exposure to traumatic events and PTSD prevalence using DSM-IV and DSM-5 criteria. Journal of Traumatic Stress, 26, 537–547. doi:10.1002/jts.21848 McLean, C. P., Asnaai, A., Litz, B. T., & Hoffman, S. G. (2011). Gender differences in anxiety disorders. Prevalence, course of illness, comorbidity and burden of illness. Journal of Psychiatric Research, 45, 1027–1035. doi:10.1016/j.jpsychires.2011.03.006 Medina-Mora, M. E., Borges, G., Benjet, C., Lara, C., & Berglund, P. (2007). Psychiatric disorders in Mexico: Lifetime prevalence in a nationally representative sample. British Journal of Psychiatry, 190, 521–528. doi:10.1192/bjp.bp.106.025841 Medina-Mora, M. E., Borges, G., Lara, C., Benjet, C., Blanco, J., Fleiz, C., Villatoro, J., . . . Zambrano, J. (2005). Prevalence, service use, and demographic correlates of 12-month DSM-IV psychiatric disorders in Mexico: Results from the Mexican National Comorbidity Survey. Psychological Medicine, 35, 1773–1783. doi:10.1017/S0033291705005672 Medina-Mora, M. E., Borges, G., Lara, C., Ramos-Lira, L., Zambrano, J., & Fleiz, C. (2005). Prevalence of violent events and post-traumatic stress disorder in the Mexican population. Salud Publica de Mexico, 47, 8–22. http://dx.doi.org/10.1590/S0036-36342005000100004 Norris, F. H., Murphy, A. D., Baker, C. K., Perrilla, J. L., Rodriguez, F. G., & Rodriguez, J. d. J. (2003). Epidemiology of trauma and posttraumatic stress disorder in Mexico. Journal of Abnormal Psychology, 112, 646–656. doi:10.1037/0021-843X.112.4.646
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Journal of Traumatic Stress DOI 10.1002/jts. Published on behalf of the International Society for Traumatic Stress Studies.
Posttraumatic Stress Disorder in a Nationally Representative Mexican Community Sample Guilherme Borges,1,3 Corina Benjet,1 Maria Petukhova,2 and Maria Elena Medina-Mora1 1
Direcci´on de Investigaciones Epidemiol´ogicas y Psicosociales, Instituto Nacional de Psiquiatr´ıa Ram´on de La Fuente Mu˜niz, Mexico City, Mexico 2 Department of Health Care Policy, Harvard Medical School, Boston, Massachusetts, USA 3 Universidad Aut´onoma Metropolitana, Mexico City, Mexico
This study describes the public health burden of trauma exposure and posttraumatic stress disorder (PTSD) in relation to the full range of traumatic events to identify the conditional risk of PTSD from each traumatic event experienced in the Mexican population and other risk factors. The representative sample comprised a subsample (N = 2,362) of the urban participants of the Mexican National Comorbidity Survey (2001−2002). We used the World Health Organization’s Composite International Diagnostic Interview (CIDI) to assess exposure to trauma and the presence of PTSD according to the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association, 1994) in each respondents’ self-reported worst traumatic event, as well as a randomly selected lifetime trauma. The results showed that traumatic events were extremely common in Mexico (68.8%). The estimate of lifetime PTSD in the whole population was 1.5%; among only those with a traumatic event it was 2.1%. The 12-month prevalence of PTSD in the whole population was 0.6%; among only those with a traumatic event it was 0.8%. Violence-related events were responsible for a large share of PTSD. Sexual violence, in particular, was one of the greatest risks for developing PTSD. These findings support the idea that trauma in Mexico should be considered a public health concern.
Traumatic events such as interpersonal violence as well as natural and manmade disasters are common risk factors in Mexico among the adult (Baker et al., 2005; Medina-Mora, Borges, Lara, Ramos-Lira, et al., 2005; Norris et al., 2003) and adolescent populations (Benjet et al., 2009; Orozco, Borges, Benjet, Medina-Mora, & L´opez-Carrillo, 2008). As expected, these events increase the risk of developing mental disorders (Benjet, Borges, M´endez, Fleiz, & Medina-Mora, 2011) and suicidality in the Mexican population (Borges et al., 2008) as they do elsewhere (Stein et al., 2010). A matter of concern is the impact of traumatic events on the development of posttraumatic stress disorder (PTSD) in Mexico. Two prior efforts in the country delved into these issues (Medina-Mora, Borges, Lara, Ramos-Lira, et al., 2005; Norris et al., 2003), but they did not present the complete spectrum of traumatic events in Mexico, and did not account for multiple traumatic events, estimating the impact of single events only on the population impact of PTSD. Because experiencing multiple traumatic events is a common situation, this was an important limitation of these studies. One of these prior reports also acknowledged that PTSD was assessed only among respondents who considered the particular event to have been their worst experience. The lack of inclusion of a randomly selected traumatic event, as well as one of the worst events, was mentioned as a limitation in this prior study in Mexico (Norris et al., 2003).
Research conducted by Guilherme Borges, Direcci´on de Investigaciones Epidemiol´ogicas y Psicosociales, Instituto Nacional de Psiquiatr´ıa Ram´on de la Fuente Mu˜n´ız. The Mexican National Comorbidity Survey is supported by The National Institute of Psychiatry Ramon de la Fuente (INPRFM-DIES 4280) and by the National Council on Science and Technology (CONACyTG30544-H), with supplemental support from the Pan American Health Organization (PAHO). The Mexican National Comorbidity Survey is carried out in conjunction with the World Health Organization World Mental Health (WMH) Survey Initiative (WMH) Survey Initiative, which is supported by the National Institute of Mental Health (NIMH; R01 MH070884 and R01 MH093612-01), the John D. and Catherine T. MacArthur Foundation, the Pfizer Foundation, the U.S. Public Health Service (R13-MH066849, R01MH069864, and R01 DA016558), the Fogarty International Center (FIRCA R03-TW006481), the Pan American Health Organization, Eli Lilly and Company, Ortho-McNeil Pharmaceutical, GlaxoSmithKline, and Bristol-Myers Squibb. We thank the staff of the WMH Data Collection and Data Analysis Coordination Centers for assistance with instrumentation, fieldwork, and consultation on data analysis. None of the funders had any role in the design, analysis, interpretation of results, or preparation of this article. A complete list of all within-country and cross-national WMH publications can be found at http://www.hcp.med.harvard.edu/wmh/. Correspondence concerning this article should be addressed to Guilherme Borges, Direcci´on de Investigaciones Epidemiol´ogicas y Psicosociales, Instituto Nacional de Psiquiatr´ıa Ram´on de la Fuente Mu˜n´ız, Mexico, Calzada M´exico Xochimilco No 101-Col. San Lorenzo Huipulco, M´exico D.F., C.P.14370 M´exico. E-mail: [email protected] or [email protected] C 2014 International Society for Traumatic Stress Studies. View Copyright this article online at wileyonlinelibrary.com DOI: 10.1002/jts.21917
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The main problem with estimates based on the worst-event approach is that the estimates of conditional risk for PTSD tend to be overestimated when compared to an estimate that also uses a random sample of all events, because worst events are not necessarily representative (Atwoli et al., 2013; Stein et al., 2012). The Mexican National Comorbidity Survey (MNCS) allowed for the first time to combine both approaches to estimate the risk of PTSD by assessing (a) PTSD associated with the worst trauma and (b) one additional trauma selected at random from all the lifetime traumas reported by each respondent. Also, when correctly weighted, these responses may be used to estimate the population prevalence and distribution of lifetime PTSD associated with the wide range of traumas assessed in the MNCS. The goals of this study were to describe the public health impact of trauma exposure and of PTSD in relation to the full range of traumatic events, and to identify the conditional risk and risk factors of PTSD in relation to each type of traumatic event experienced in the Mexican population.
Method Participants and Procedure The MNCS is part of the World Health Organization’s World Mental Health Survey Initiative (Demyttenaere et al., 2004). The survey was based on a stratified, multistage area probability sample of noninstitutionalized persons aged 18 to 65 years living in urban areas (population 2,500+) of Mexico. About 75% of the Mexican population is urban and meets the above definition. Data collection took place from September 2001 through May 2002. The response rate was 76.6% for a total 5,782 respondents. All respondents were administered a Part I interview; to decrease the burden of a long interview process, only a selected subsample of 2,362 received a Part II interview. The Part II interview included questions on supplemental psychiatric disorders and traumatic events, and thus are the study participants. The sample receiving Part II consisted of all respondents who screened positive for any disorder in Part I plus a subgroup of persons without symptoms. About one third of those who screened negative in the Part I interview were randomly assigned to the Part II interview. The subsample was then normalized, taking into account the probability of selection, to match the characteristics of the complete sample. There was a random selection process embedded into a computer algorithm for the selection of those screening negative in the first phase of the survey. All interviews were conducted at the respondents’ home after a careful description of the study goals was provided and informed consent was obtained. All recruitment and consent procedures were approved by the ethics committee of the National Institute of Psychiatry. Additional details of this study and sample have been published elsewhere (Medina-Mora, Borges, Lara, Benjet et al., 2005).
Measures Mental disorders including PTSD were defined by the Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSMIV; American Psychiatric Association, 1994) and assessed with version 3.0 of the World Health Organization Composite International Diagnostic Interview (CIDI), a fully structured, computer assisted diagnostic interview administered face-to-face by trained lay interviewers. The World Health Organization translation protocol was used to translate the questionnaire (Kessler ¨ un, 2004; Robins et al., 1988). & Ust¨ The CIDI measures 29 different lifetime traumatic events and their ages of occurrence with questions such as “Were you ever involved in a very serious or life-threatening car accident?” Traumatic events were categorized into seven event classes as follows: war events, physical violence, sexual violence, accidents, death, and network events involving others. An additional question inquired about other traumatic events not included in the CIDI list. After the list of events was assessed, the respondent was asked if there was any other event that he or she suffered that had not been asked about in the prior list or which did not fit in any of the former categories. In this case, respondents were asked to give details about the event and this was recorded verbatim. Finally, the respondent was also able to select a private event category, which was reserved for traumas for which the respondent did not feel comfortable providing details or disclosing the nature of the trauma, also included in the Other category. Those who answered affirmatively on the occurrence of a lifetime event were also asked whether that event occurred within the last 12 months. Lifetime PTSD was assessed twice in the survey: once based on PTSD associated with the respondents’ self-reported worst lifetime trauma, and a second time based on one randomly selected trauma from all those reported by the respondent as ever having occurred to him or her. The randomly selected event was used to compensate for the fact that when PTSD rates are calculated using only the worst traumas that are atypical, the risk of PTSD may well be higher than for more typical traumas. Weights were applied to the randomly selected traumatic events to adjust for the fact that they represent only a sample of the respondent’s lifetime traumas. This produced a weighted dataset in which each trauma was represented in the proportion it occurred in the population. The remaining criteria for PTSD were assessed for each worst event and each random event. Criterion A2 was considered met if the respondent endorsed any of the three questions about whether at the time of the traumatic event, he or she felt terrified or very frightened, helpless, shocked, or horrified. The remaining criteria were then assessed whether or not A2 was endorsed with structured questions about reexperiencing (Criterion B), avoidance-numbing (Criterion C), arousal (Criterion D), duration (Criterion E), and clinically significant distress or impairment (Criterion F). A retrospective question also asked respondents for how many months or years symptoms continued. Responses to this question were used to define PTSD persistence. The 12-month prevalence of PTSD
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was assessed among those with a 12-month event in a similar fashion. Data Analysis We used a design-based statistical analysis strategy for point and variance estimates and hypothesis testing, using standard survey data analysis procedures to account for design effects arising from the use of stratification, clustering, and unequal selection probabilities in the surveys and weights (Efron, 1988; Wolter, 1985). Based on respondents’ reports of their lifetime history of traumatic events, including the age at each event, we estimated the rates of trauma exposure using standard life table methods. We used a logistic regression model to study variation in the risk of first onset of PTSD by trauma types and sociodemographics, for both 12-month and lifetime PTSD (Hosmer & Lemeshow, 2000). Design-based standard errors for logistic regression coefficients and for pairwise contrasts between them were estimated using the Taylor linearization method with SUDAAN version 10.0141 (Research Triangle Institute, 2009) and were used in Wald tests for statistical significance and for producing 95% confidence intervals (CIs) for adjusted hazard ratios (Wolter, 1985). The first logistic regression model tested whether sociodemographics were associated with lifetime and 12-month PTSD in the population. The second model then evaluated the extent to which the coefficients in the first model changed with the focus only on respondents who were exposed to one or more traumas, adjusted for the classes of traumas implicated in the possible PTSD.
of developing PTSD following that event. In Table 2, we show that some events that have a high risk of PTSD are nevertheless rare and contribute little to the burden of PTSD, such as being a refugee, which was extremely rare (see Table 1). Thus, the class of events of physical violence (34.4%) and network events (20.9%) stand out as the main contributors to the burden of PTSD in Mexico. The two main events responsible for the largest burden of PTSD were having accidentally caused serious injury or death (13.7%) and having been sexually assaulted (13.6%). Finally, even when the symptoms associated with most events tended to be very persistent, there was a large variation in the duration of PTSD depending on the event. The variables associated with having lifetime PTSD in the total sample were being female (increasing the likelihood of PTSD by 4.8 times), and being both in the low-average and highaverage educational groups as they had lower odds ratios (ORs) for PTSD when compared to those in the high education group (Table 3). The analysis of lifetime PTSD among respondents with traumatic events, with type of event in the model, showed that none of the prior variables remained associated with PTSD except sex and being retired. A similar set of analyses were performed for 12-month PTSD (prevalence of 0.6%, 29 cases only, among the whole population and 0.8% among those with a traumatic event). The only variable that showed an association with 12-month PTSD was employment status; being unemployed, a student, or retired showed a very high likelihood of PTSD in comparison to being employed (OR = 6.56) in the total sample and among those with the traumatic events (OR = 9.81; full results not shown).
Results
Discussion
As shown in Table 1, 68.8% of the Mexican population suffered a trauma in their lifetime, with physical violence being the most common class (42.2% of the population and 28.5% as a percentage of all traumatic events), followed by network events (36.5% of the population and 24.5% as a percentage of all traumatic events). The single most common trauma was being mugged or threatened with a weapon (24.6%), followed by the unexpected death of loved one (22.7%). The lifetime prevalence of PTSD was 1.5% (68 cases) and among respondents with traumatic events the lifetime prevalence of PTSD was 2.1%. Table 2 presents the lifetime prevalence of PTSD by events and classes of events, as well as by percentage of all PTSD cases, and the duration of PTSD. Among event classes, other events had the highest risk of PTSD at 3.1%, followed by sexual violence, with a 2.6% prevalence of PTSD. For individual events, the highest risk of PTSD was associated with being a refugee (84.8%), accidentally caused serious injury or death (11.1%), those reporting a private event (4.2%), and sexual assault (3.8%). All other traumas had a lower comparative prevalence (0.0−3.2%). The burden of PTSD in the population is a joint function of the prevalence of the traumatic event and the conditional risk
The main findings of this research suggest that traumatic events are extremely common in urban Mexico (68.8%), but that lifetime PTSD is much less frequent (1.5%) in the whole population or among those with a traumatic event (2.1%). Despite some events significantly increasing the likelihood of subsequent PTSD (such as being a refugee in Mexico), they were so rare that their population burden was minimal. Other events, however, such as being sexually assaulted, stand out as particularly deleterious in Mexico due to the combination of a large likelihood of PTSD and a greater frequency of occurrence. Few demographic factors showed an association with PTSD, either lifetime or recent (12 month). Among them, being female and more educated had larger ORs for lifetime PTSD and being unemployed, a student, and retired had an increased likelihood of 12-month PTSD. Although the prevalence of PTSD was low, the duration of PTSD symptoms was particularly long, on average more than 5 years, but ranging from 4 months to 27 years depending on the type of event. The unusually long duration of PTSD in Mexico probably reflects the lack of service utilization in Mexico for this disorder, as well as long delays in seeking treatment. Prior research has suggested that 12-month service utilization in Mexico for mental health problems is 18.6% of those with
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Table 1 Prevalence of Traumas in the Mexican National Comorbidity Survey Event type No events War events Combat experience Relief worker in war zone Civilian in war zone Civilian in region of terror Refugee Injured, tortured, killed other Saw atrocities Accidents Toxic chemical exposure Automobile accident Other life threatening accident Natural disaster Man-made disaster Life-threatening illness Unexpected death of loved one Physical violence Kidnapped Beaten by caregiver Beaten by spouse or partner Beaten up by someone else Mugged, threat by weapon Sexual violence Raped Sexually assaulted Stalked Network events Child with serious illness Traumatic event to loved one Accidentally caused serious injury or death Saw death/dead body, or saw other seriously hurt Saw physical fight at home Others Some other event Private event Total with any event
Unweighted n
Weighted %
SE
% of all events
SE
17 0 1 2 5 2 2 5 428 27 132 37 104 20 108 273 572 19 194 98 53 208 134 36 71 27 430 67 32 6 146 179 60 12 48 1914
31.2 1.7 0.0 0.2 0.1 0.8 0.0 0.4 0.5 35.2 4.1 15.3 5.1 12.2 2.3 10.0 22.7 42.2 2.2 18.3 6.0 7.4 24.6 10.0 3.9 5.4 3.7 36.5 7.2 3.5 1.3 16.3 20.3 4.9 1.4 3.8 68.8
1.76 0.29 0.02 0.08 0.05 0.18 0.03 0.13 0.15 1.54 0.62 1.22 0.52 1.26 0.38 0.90 1.39 1.70 0.33 1.00 0.51 0.75 1.22 0.82 0.49 0.67 0.59 1.54 0.84 0.38 0.24 1.09 1.16 0.53 0.29 0.38 1.76
0.8 0.0 0.1 0.0 0.3 0.0 0.2 0.2 24.7 3.4 6.8 2.5 6.7 0.9 4.5 12.1 28.5 0.8 6.4 2.1 4.3 14.9 7.6 2.5 3.1 2.0 24.5 3.0 1.4 1.1 12.0 7.1 1.8 0.5 1.3 100
0.14 0.01 0.03 0.02 0.06 0.01 0.09 0.06 1.23 0.68 0.48 0.31 0.95 0.14 0.53 1.01 1.05 0.10 0.33 0.17 0.55 0.78 0.73 0.52 0.36 0.31 0.93 0.39 0.18 0.34 0.91 0.33 0.20 0.1 0.14 0.00
Note. N = 2,362. SE = standard error.
mental health needs (Borges et al., 2006), and although many people with lifetime disorders eventually made treatment contact, delays were long: 10 years for substance use disorders, 14 years for mood disorders, and 30 years for anxiety disorders (Borges, Wang, Medina-Mora, Lara, & Chiu, 2007). Treatment latency in Mexico is among the longest in a comparison of 15 countries around the world (Wang et al., 2007).Our group has reported previously on the prevalence of traumatic events and PTSD in Mexico (Medina-Mora, Borges, Lara, Ramos-Lira, et al., 2005; Medina-Mora, Borges, Benjet, Lara, & Berglund, 2007), whereas others (Norris et al., 2003) have reported es-
timates of PTSD for a smaller group of cities from Mexico and for a smaller set of negative life-events with estimations as high as 11.2%. Nevertheless, this is the first report of PTSD for Mexico that takes into account both the most severe (worst) and a random sample of all events. Thus, the estimates provided here of the impact of traumatic events on the occurrence of PTSD are more conservative. These estimates point to a low conditional risk for PTSD associated with most events in contrast to the previous study in Mexico. Research from a group of European countries (Darves-Bornoz et al., 2008) reported a 12-month prevalence of PTSD of 1.1%, higher than our
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Table 2 Prevalence of Lifetime PTSD by Events in the Mexican National Comorbidity Survey
na
Event type War events Combat experience Relief worker in war zone Civilian in war zone Civilian in region of terror Refugee Injured, tortured, killed other Saw atrocities Accidents Toxic chemical exposure Automobile accident Other life threatening accident Natural disaster Man-made disaster Life-threatening illness Unexpected death of loved one Physical violence Kidnapped Beaten by caregiver Beaten by spouse or romantic partner Beaten up by someone else Mugged, threat by weapon Sexual violence Raped Sexually assaulted Stalked Network events Child with serious illness Traumatic event to loved one Accidentally caused serious injury or death Saw death/dead body, or saw other seriously hurt Saw physical fight at home Others Some other event Private event Total with any event
1
1
7 4 3
9 23 3 5 9 2 4 17 6 9 2 5 2 1
2 9 1 8 71
PTSD episode (or residual symptoms in months)
Probability of PTSD (%)b
SE
% of all PTSD cases
SE
Mean duration
SE
1.1 – 0.0 0.0 0.0 84.8 0.0 0.0 0.3 0.0 0.9 0.0 0.3 0.0 0.0 0.3 1.0 3.2 1.5 3.1 0.2 0.7 2.6 1.2 3.8 2.3 0.7 0.7 0.0 11.1
1.05 – 0.00 0.00 0.00 18.20 0.00 0.00 0.16 0.00 0.56 0.00 0.18 0.00 0.00 0.13 0.29 2.51 0.82 1.45 0.14 0.39 1.18 0.61 1.67 2.30 0.61 0.62 0.00 11.10
1.0 – – – – 1.0 – – 9.5 – 7.4 – 2.1 – – 4.8 34.4 2.8 11.0 7.4 1.0 12.2 22.4 3.3 13.6 5.5 20.9 2.6 – 13.7
1.07 – – – – 1.07 – – 4.77 – 4.58 – 1.26 – – 1.99 9.10 2.29 5.21 3.56 0.67 6.39 8.31 2.02 5.88 5.01 15.01 2.17 – 8.61
324.0
0.0
324.0
0.0
37.1
6.2
41.4
7.5
22.2
11.0
16.6 79.7 4.8 112.8 145.1 6.7 33.3 125.1 164.3 161.6 11.5 12.0 9.8
4.7 29.0 2.0 59.0 60.0 2.0 19.0 40.0 48.0 59.0 0.7 16.0 2.4
4.0
0.0
0.0
0.00
–
–
0.6 3.1 0.6 4.2 0.9
0.45 1.34 0.65 1.95 0.39
4.7 6.9 0.3 6.5 100.0
36.5 32.8 60.0 31.0 67.9
27.0 19.0 0.0 20.0 40.0
3.55 3.44 0.14 3.42 0.00
Note. N = 2,362. PTSD = posttraumatic stress disorder; SE = standard error. a n is unweighted. b % is weighted.
estimate of 0.6%. The reason for the difference in prevalence of PTSD across countries or studies is poorly understood. Besides differences in the prevalence of events and their impact on PTSD, which seem mostly attributable to methodological differences in terms of the samples and types of events surveyed, all reports similarly point to the large role of violence-
related events as responsible for a large share of PTSD, and especially sexual violence as one of the most prevalent and with the greatest risk for developing PTSD. Methodological differences among studies, cultural differences in symptom presentation, and cultural differences with respect to factors contributing to risk and resilience following trauma
Journal of Traumatic Stress DOI 10.1002/jts. Published on behalf of the International Society for Traumatic Stress Studies.
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Borges et al.
Table 3 Demographic Correlates of Lifetime PTSD in the Mexican National Comorbidity Survey Predict LT PTSD among respondents with events, controlling for events
Total sample Variable
OR
Sex Male 1.00 Female 4.77 Age (years) 18−29 1.51 30−44 1.28 45−59 1.06 60+ 1.00 Marital status Married 1.00 Previously married 1.72 Never married 0.50 Education Low 0.64 Low-average 0.32 High-average 0.34 High 1.00 Employment status Working 1.00 Student 1.54 Homemaker 1.15 Retired 2.66 Other including unemployed 2.05 Type of random or worst event that was assessed for PTSD War events – Physical violence – Sexual violence – Accidents – Death – Network events – Other or private – Count of prior events Prior war events – Prior physical violence – Prior sexual violence – Prior accidents – Prior deaths – Prior network events – Prior other events –
95% CI
OR
95% CI
[1.0, 1.0] [1.25, 18.24]
1.00 4.51
[1.0, 1.0] [0.97, 20.77]
[0.41, 5.53] [0.55, 3.00] [0.29, 3.83] [1.0, 1.0]
3.68 2.21 2.01 1.00
[0.96, 14.03] [0.73, 6.70] [0.49, 8.11] [1.0, 1.0]
[1.0, 1.0] [0.65, 4.54] [0.22, 1.12]
1.00 1.49 0.85
[1.0, 1.0] [0.34, 6.47] [0.26, 2.77]
[0.22, 1.85] [0.10, 0.96] [0.15, 0.78] [1.0, 1.0]
1.11 0.32 0.50 1.00
[0.39, 3.12] [0.10, 1.01] [0.21, 1.20] [1.0, 1.0]
[1.0, 1.0] [0.30, 7.87] [0.40, 3.27] [0.38, 18.67] [0.45, 9.26]
1.00 1.81 2.11 11.52 5.90
[1.0, 1.0] [0.37, 8.88] [0.66, 6.73] [1.28, 103.31] [0.89, 38.91]
– – – – – – –
6.63 5.32 5.81 1.67 1.00 2.64 9.20
[0.61, 71.11] [1.67, 16.98] [1.29, 26.08] [0.44, 6.36] [1.0, 1.0] [0.49, 14.27] [2.26, 37.33]
– – – – – – –
1.16 1.31 0.96 1.14 1.02 0.95 0.70
[0.33, 3.70] [0.973,1.77] [0.69,1.33] [0.87, 1.51] [0.53, 1.97] [0.682, 1.33] [0.14, 3.58]
Note. N = 2,362. PTSD = posttraumatic stress disorder. LT PTSD = long-term posttraumatic stress disorder.
exposure could also explain some of the differences in the prevalence rates found here among studies. Familism, conceptualized as family cohesiveness combined with familial obligations, is a cultural trait often described in the Mexican population (Almeidia, Molnar, Kawachi, & Subramanian, 2009; Sabogal, Mar´ın, Otero-Sabogal, & Mar´ın, 1987). Although our current study
cannot address this hypothesis, the social support afforded by familism may play a protective role on the risk for developing PTSD following a traumatic event as it does for protecting against other negative health conditions in those of Mexican origin (Gallo, Penedo, Espinosa de los Monteros, & Arguelles, 2009; Germ´an, Gonzales, & Dumka, 2009).
Journal of Traumatic Stress DOI 10.1002/jts. Published on behalf of the International Society for Traumatic Stress Studies.
Posttraumatic Stress Disorder in Mexicans
Our results on the large and deleterious role of interpersonal violence and sexual events in Mexico are also in tandem with results on the impact of such events on suicidality (Borges et al., 2008) and on other mental disorders. The relatively low conditional probability of PTSD suggests that PTSD may not be the only or even the most common reaction to traumatic events. Although a good number of people may have sufficient coping resources to recover from trauma, research on the impact of trauma on other mental health conditions such as depression, anxiety, substance use disorders, and suicidality (Benjet et al., 2011; Borges et al., 2008; Stein et al., 2010) suggest that these may be alternative common responses to trauma (Borges et al., 2008). Our study is one of the first in the country that we are aware of to study factors associated with lifetime and 12-month PTSD in a sample of the general urban population. Being female was associated with lifetime PTSD, but not with 12-month PTSD. Prior epidemiological studies overwhelmingly report higher prevalence estimates for females than for males (Breslau & Anthony, 2007; Kessler, Sonnega, Bromet, Hughes, & Nelson, 1995; McLean, Asnaai, Litz, & Hoffman, 2011; Norris et al., 2003). These findings are largely consistent with basic research and animal studies that posit that a greater female vulnerability to traumatic events is due to differences in the stress response system at a biological level such as differences in corticotrophin-releasing factor functioning and the locus coeruleus-norepinephrine system, which contribute to increased stress sensitivity and hyperarousal in females (Bangasser & Valentino, 2012; Ressler et al., 2011). With regard to education and employment, lower educational levels and being employed were associated with lower lifetime and 12-month PTSD odds, respectively. The mechanisms that might account for this are still unclear. Our results should be framed in the context of the main limitations of this research. The information on lifetime events and dating of PTSD symptoms were obtained by self-report and may be subject to recall bias, forgetting, or willingness to report distressing traumatic events. Nevertheless, our survey estimates should be interpreted as lower estimates. It is more likely that these potential biases led to conservative estimates of the frequency of events and of the total prevalence of PTSD. This report used DSM-IV diagnostic criteria and because changes in the new DSM-5 only seem to slightly decrease the prevalence of PTSD (Kilpatrick et al., 2013) we believe that our current DSM-IV estimates can be used with confidence in Mexico, until new research with updated criteria are reported.
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Atwoli, L., Stein, D. J., Williams, D. R., McLaughlin, K. A., Petukhova, M., Kessler, R. C., & Koenen, K. C. (2013). Trauma and posttraumatic stress disorder in South Africa: Analysis from the South African Stress and Health Study. BMC Psychiatry, 13, 182. doi:10.1186/1471-244X-13-182 Baker, C. K., Norris, F. H., Diaz, D. M., Perilla, J. L., Murphy, A. D., & Hill, E. G. (2005). Violence and PTSD in Mexico: Gender and regional differences. Social Psychiatry and Psychiatric Epidemiology, 40, 519–528. doi:10.1007/s00127-005-0921-2 Bangasser, D. A., & Valentino, R. J. (2012). Sex differences in molecular and cellular substrates of stress. Cellular and Molecular Neurobiology, 32, 709–723. doi:10.1007/s10571-012-9824-4 Benjet, C., Borges, G., Medina-Mora, M. E., Zambrano, J., Cruz, C., & M´endez, E. (2009). Descriptive epidemiology of chronic childhood adversity in Mexican adolescents. Journal of Adolescent Health, 45, 483–489. doi:10.1016/j.jadohealth.2009.03.002 Benjet, C., Borges, G., M´endez, E., Fleiz, C., & Medina-Mora, M. E. (2011). The association of chronic adversity with psychiatric disorder and disorder severity in adolescents. European Child and Adolescent Psychiatry, 20, 459–468. doi:10.1007/s00787-011-0199-8 Borges, G., Benjet, C., Medina-Mora, M. E., Orozco, R., Molnar, B. E., & Nock, M. K. (2008). Traumatic events and suicide-related outcomes among Mexico City adolescents. Journal of Child Psychology and Psychiatry, 49, 654–666. doi:10.1111/j.1469-7610.2007.01868.x Borges, G., Medina-Mora, M. E., Wang, P., Lara, C., Berglund, P., & Walters, E. (2006). Treatment and adequacy of treatment of mental disorders among respondents to the Mexico National Comorbidity Survey. American Journal of Psychiatry, 163, 1371–1378. doi:10.1176/appi.ajp.163.8.1371 Borges, G., Wang, P. S., Medina-Mora, M. E., Lara, C., & Chiu, W. T. (2007). Delay of first treatment of mental and substance use disorders in Mexico. American Journal of Public Health, 97, 1638–1643. doi:10.2105/AJPH.2006.090985 Breslau, N., & Anthony, J. C. (2007). Gender differences in the sensitivity to posttraumatic stress disorder: An epidemiological study of urban young adults. Journal of Abnormal Psychology, 116, 607–611. doi:10.1037/0021843X.116.3.607 Darves-Bornoz, J. M., Alonso, J., de Girolamo, G., de Graaf, R., Haro, J. M., Kovess-Masfety, V., (2008) ESEMeD/MHEDEA 2000 Investigators. Main traumatic events in Europe: PTSD in the European study of the epidemiology of mental disorders survey. Journal of Traumatic Stress, 21, 455–462. doi:10.1002/jts.20357 Demyttenaere, K., Bruffaerts, R., Posada-Villa, J., Gasquet, I., Kovess, V., Lepine, J. P., . . . Chatterji, S. (2004). Prevalence, severity and unmet need for treatment of mental disorders in the World Health Organization World Mental Health Surveys. Journal of the American Medical Association, 291, 2581–2590. doi:10.1001/jama.291.21.2581 Efron, B. (1988). Logistic regression, survival analysis, and the KaplanMeier curve. Journal of the American Statistical Association, 83, 414–425. doi:10.1080/01621459.1988.10478612
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Journal of Traumatic Stress DOI 10.1002/jts. Published on behalf of the International Society for Traumatic Stress Studies.
