http://informahealthcare.com/ada ISSN: 0095-2990 (print), 1097-9891 (electronic) Am J Drug Alcohol Abuse, 2014; 40(4): 269–273 ! 2014 Informa Healthcare USA, Inc. DOI: 10.3109/00952990.2014.910520
Does the legalization of medical marijuana increase completed suicide? Melanie Rylander, MD1,2,4, Carolyn Valdez, MS3, and Abraham M. Nussbaum, MD1,4 1
Departments of Behavioral Health, 2Departments of Internal Medicine, 3Departments of Patient Safety and Quality, Denver Health, Denver, Colorado, and 4Department of Psychiatry, University of Colorado School of Medicine, Colorado, USA
Introduction: Suicide is among the 10 most common causes of death in the United States. Researchers have identified a number of factors associated with completed suicide, including marijuana use, and increased land elevation. Colorado is an ideal state to test the strength of these associations. The state has a completed suicide rate well above the national average and over the past 15 years has permitted first the medical and, as 2014, the recreational use of marijuana. Objectives: To determine if there is a correlation between medical marijuana use, as assessed by the number of medical marijuana registrants and completed suicides per county in Colorado. Methods: The number of medical marijuana registrants was used as a proxy for marijuana use. Analysis variables included total medical marijuana registrants, medical marijuana dispensaries per county, total suicide deaths, mechanism of suicide death, gender, total suicide hospitalizations, total unemployment, and county-level information such as mean elevation and whether the county was urban or rural. Analysis was performed with mixed model Poisson regression using generalized linear modeling techniques. Results: We found no consistent association between the number of marijuana registrants and completed suicide after controlling for multiple known risk factors for completed suicide. Conclusion: The legalization of medical marijuana may not have an adverse impact on suicide rates. Given the concern for the increased use of marijuana after its legalization, our negative findings provide some reassurance. However, this conclusion needs to be examined in light of the limitations of our study and may not be generalizable to those with existing severe mental illness. This finding may have significant public health implications for the presumable increase in marijuana use that may follow legalization.
Altitude, cannabis, legalization of marijuana, medical marijuana, suicide, unemployment
Introduction Colorado has received national attention for its approach to marijuana. In 2000, a citizen-initiated amendment to the state constitution allowed for the medical use of marijuana. After the federal government announced in 2009 (1) that it would not routinely prosecute users and distributors, the number of registrants to the state’s medical marijuana registry increased dramatically. By 2011, more than 2% of the state’s population had registered to use marijuana for a medical purpose (2). Concerns have been raised that the criteria to obtain a medical marijuana card is extremely broad, and that many of those on the medical marijuana registry are recreational users who have found a way to obtain the drug legally (2,3). Thus, the population of medical marijuana users may be very similar to general recreational users. In 2012, another
Address correspondence to Melanie Rylander, MD, Departments of Behavioral Health and Internal Medicine, Denver Health, 777 Bannock Street, MC 0490, Denver, CO 80204-4507, USA. Tel: +1 303 602 6938. Fax: +1 303 602 6930. E-mail: [email protected]
History Received 18 November 2013 Revised 19 March 2014 Accepted 23 March 2014 Published online 20 June 2014
citizen-initiated amendment legalized the possession, distribution, and recreational use of one ounce or less of marijuana. Simultaneously, members of the Colorado psychiatric community have voiced concerns regarding the adverse psychiatric effects of marijuana use, especially with regards to suicide (3). In large cohort studies, the association of marijuana use and suicide has been inconsistent (4–9). Degenhardt et al. examined a series of cohort and cross sectional studies and found a modest association for heavy or problematic cannabis use and depressive symptoms. They also found a modest association between early onset regular cannabis use and later onset depression. No association was found for baseline depression with later onset of cannabis use, arguing against the self-medication hypothesis (4). Lynskey et al. examined same sex twin pairs discordant for cannabis dependence to determine relationships between cannabis use and major depressive disorder, suicidal behavior, and suicidal ideations. Cannabis-dependent individuals had an odds of suicide attempt or ideation that was 2.5–2.9 times higher than their non-cannabis-dependent twin. Those who initiated use prior to age 17 had 3.5 times the rate of subsequent suicide attempts (5). Pedersen et al. also observed increased rates of
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suicide attempts in cannabis users even after controlling for confounders (6). Rasic et al. found no association between cannabis use and suicide amongst high school student though did observe an association between heavy use and depression but not suicidal ideations or attempts (7). In a 30-year longitudinal study, van Ours et al. found that intensive cannabis use, defined as several times per week, was associated with later onset of suicidal ideations amongst males but not females after controlling for confounders (8). However, not all studies support these findings. In a longitudinal study of over 50,000 men, Price et al. found no association between cannabis use and suicides after controlling for psychological and behavior problems (9). The positive associations are particularly concerning for a state like Colorado, where the prevalence of both completed suicides and marijuana use exceed the national averages. Between 2000 and 2010, the age-adjusted national rate of completed suicide was 11.2 per 100,000; in Colorado, the rate was 16.3 per 100,000 (10,11). Thus, the relationship between marijuana use and suicide remains unclear. Differences in study populations, designs, and controlled confounders likely explain much of the discrepancy in findings. To date, no studies have examined the relationships between medical marijuana use and completed suicides in Colorado. The legalization of medical marijuana may increase the frequency and intensity of marijuana use (12). States that have legalized medical marijuana have been found to have higher rates of marijuana use. Given the concerns raised about potential adverse psychiatric effects of marijuana use, this may increase psychiatric morbidity and mortality. However, a recent study by Anderson et al. found that legalization of medical marijuana across all states was not associated with increased suicide rates (13). Colorado is an ideal state to explore the association between suicide and marijuana use, not only because of the prevalence of medical marijuana use and completed suicide, but because the state regulates the use of medical marijuana. The Colorado Department of Public Health and Environment (CDPHE) has maintained a registry of medical marijuana users since 2000, which provides anonymous demographic information about registrants. In addition, the CDPHE also maintains a database of completed suicides. Examining correlations between these data sets after controlling for other known risk factors for suicide may give insight into if and how medical marijuana use impacts the prevalence of completed suicide. Furthermore, because medical marijuana users may be similar to the general population and recreational users (14), the impact of medical marijuana use on suicide rates may have implications for the general population in a state with legalized recreational marijuana. In addition to established risk factors such as unemployment and living in a rural community, we also controlled for elevation as this has been associated with suicide even after controlling for traditional risk factors such as age, male gender, unemployment, and access to firearms (15,16). In a state with mountainous regions such as Colorado, altitude may be a significant risk factor for suicide that needs to be incorporated into statistical models (15,16).
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Methods Data collection and sources The CDPHE provided county-level data for the number of suicides per year, number of suicide-related hospitalizations, mechanism of suicide death, gender of suicide completers and age, and number of individuals on the medical marijuana registry for all 64 counties in Colorado. Medical marijuana registrants were used as a proxy for marijuana use. Although the medical use of marijuana was permitted in November 2000, we restricted our analysis to CDPHE data gathered from 2004–2010. Prior to 2004, the collection and recording of data from the medical marijuana registry was irregular, leaving several gaps in the data which rendered its analysis unfeasible. During 2011, the number of registrants began to decline without clear explanation. The CDPHE speculates (personal communication) that the decline was due to patients delaying renewal because they anticipated decreased registration fees and concerns that the confidentiality of the registry was compromised and might affect employment or the ability to purchase firearms or ammunition. Since we could not assess these possibilities, we excluded all data after 2010 because the irregularities in the data after 2010 made it unreliable for analysis. In addition, we used the number of medical marijuana dispensaries per county as a proxy for use in that county. Addresses for marijuana dispensaries were matched to individual counties by zip code. Unemployment data were obtained from Colorado Department of Labor and Employment (CDLE), and the mean elevation of individual counties was also obtained from the National Geographic Survey (NGS). Designation of counties as urban versus rural was obtained from CDPHE. Data analysis Analysis variables included total medical marijuana registrants, medical marijuana dispensaries per county, total suicide deaths, mechanism of suicide death (firearm, hanging, poison, other), gender, total suicide hospitalizations, total unemployment, and county-level information such as mean elevation and whether the county was urban or rural. Total medical marijuana registrants per county, per year and medical marijuana dispensaries per county were the main explanatory variables and total suicide deaths was the main dependent variable, total unemployment was a secondary explanatory variable. Total registrants, total suicide deaths, total suicide hospitalizations, total unemployment, and mean county elevation were all count data, whereas county type (rural/urban) was categorical. Data were first examined for any existing associations. This was done by stratifying count data by year and analyzing the correlation between two variables at a time. Count data had to be log-transformed in order to make them normal and meet the criteria for correlation analyses to be performed. Analysis was performed on count and categorical data for all Colorado counties and included years. All analyses were conducted using SAS Statistical Software Version 9.3 (SAS Institute, Cary, NC, USA). Analysis was performed
Correlations between medical marijuana and suicide
Figure 1. Medical Marijuana Registrants in Colorado from 2004–2010 (primary axis) and Completed Suicides in Colorado from 2004–2010 (secondary axis). Source: CDPHE.
900 120000 800 700 600
40000 Total Registrants Total Suicide Deaths
20000 100 0
Table 1. The range, means, and standard deviations for completed suicides, medical marijuana registrants, and unemployment. Year
Total suicide deaths Registrants Total unemployment Total suicide deaths Registrants Total unemployment Total suicide deaths Registrants Total unemployment Total suicide deaths Registrants Total unemployment Total suicide deaths Registrants Total unemployment Total suicide deaths Registrants Total unemployment Total suicide deaths Registrants Total unemployment
Table 2. Pearson Correlation Coefficients by year for two-way correlations between each of the key variables. 2004 2005 2006 2007 2008 2009 2010 log10(Suicide deaths) 0.41 0.53 0.60 0.61 0.68 0.70 0.70 log10(MMJ registrants) 0.73 0.73 0.74 0.75 0.77 0.79 0.71 log10(Suicide deaths) log10(Unemployment) log10(MMJ registrants) 0.80 0.83 0.84 0.86 0.91 0.94 0.96 log10(Unemployment) All correlations were significant at the ¼ 0.05 level. MMJ, Medical marijuana.
with mixed model Poisson regression using generalized linear modeling techniques.
Results Figure 1 shows the number of individuals on the medical marijuana registry from 2004–2010 as well as the total number of suicides in Colorado over the same time. Registrants steadily increased up until 2009 when there was an exponential increase in registrants, following the federal government’s announcement that they would not pursue prosecution. During the same period, completed suicides ranged from 792–940 per 100,000. Table 1 shows the range, means, and standard deviations for completed suicides, medical marijuana registrants, and unemployment. Table 2 displays the unadjusted Pearson Correlation Coefficients by year for each of the key log-transformed variables. All correlations were strong and statistically significant with the correlation between unemployment and medical marijuana use being the highest. However, the correlation between suicide deaths per year per county and medical marijuana registrants per year per county disappeared when unemployment rates per year per county were factored in (Table 3). When adjusting for medical marijuana registrants, the correlation between unemployment rates and suicides remained significant (Table 3). Separating suicides by age, gender, or method did not alter our results. After adjusting for unemployment, mean county elevation, and urban versus rural county status, medical marijuana registrants per year was not a significant predictor of suicide rates (p ¼ 0.13) (Table 3). Urban counties were associated with a higher suicide rate (p50.001) after adjusting for unemployment, mean county elevation, and medical marijuana registrants. Mean elevation by county was associated with lower suicide rates but this association disappeared after adjusting for urban versus rural status, unemployment, and medical marijuana registrants (Table 4). There was no relationship between maximum or mean
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Am J Drug Alcohol Abuse, 2014; 40(4): 269–273
Table 3. Pearson Partial Correlation Coefficients by year for two-way correlations between each of the key variables.
Table 4. Results for mixed model Poisson regression for completed suicides. Type III tests of fixed effects Effect Year MMJ registrants Total unemployment Maximum county elevation Urban county
6 1 1 1 1
430 430 430 52.91 45.18
6.7 2.35 7.64 1.33 40.3
50.0001 0.1256 0.006 0.2534 50.0001
MMJ, Medical marijuana.
county elevation and number of medical marijuana registrants (Table 5). The medical marijuana registry is only a by-proxy measure of medical marijuana use, because a person could register for permission to use medical marijuana without consuming marijuana and some dispensaries may inconsistently verify registry cards. A subsequent analysis exploring the relationship between the number of medical marijuana dispensaries per county and per county suicides did not identify a significant relationship between the number of marijuana dispensaries per county and suicides.
Discussion Our results did not show a significant correlation between the number of medical marijuana registrants and suicides. Although prior studies have shown positive correlations with marijuana use and suicide attempts and suicidal ideations even after adjusting for anxiety, depression, and stressful life events, the role of marijuana use in completed suicides remains unclear (6,8). The difficulty in conducting research on the role of medical marijuana use in suicide completions is a reflection of the small number of suicides, limitations in obtaining accurate information on marijuana use in deceased subjects, and controlling for confounding factors such as comorbid substance use, depression and anxiety. While previous studies have found that marijuana use was a significant independent risk factor for suicidal behaviors in high school students after controlling for anxiety and depression (17), suicide completers represents a different population than those engaged in suicidal behaviors, and it is unclear whether this data can be extrapolated. Additionally, medical marijuana users may be different from general users though data suggests that medical marijuana users are not different from the general population (14). The lack of correlation between unemployment and suicides after adjusting for county elevation and urban versus rural status was surprising and not readily explainable. Similarly, the lack of correlation between county elevation
and suicides was also surprising given prior studies showing positive correlations after adjusting for age, gender, income, and gun ownership (15,16). These studies focused on state-bystate data whereby our data was restricted to the state of Colorado. In the absence of attempts to replicate this finding, it is unclear if the restriction to one state alters this association or if there is a unique confounder in Colorado. Our study did show significant positive correlations with medical marijuana registrants and unemployment. Analysis of medical marijuana use on gaining and maintaining employment is beyond the scope of this study. However, this relationship warrants further investigation particularly in light of the recent legalization of marijuana. There are several limitations to our study. The first is that the medical marijuana registry is a proxy measure of marijuana use. At this time, it is not possible to obtain accurate data about the number of marijuana users in Colorado or to quantify that use. Individuals on the medical marijuana registry may not represent marijuana users in the general populations. However, there has been speculation that because of the broad eligibility criteria and minimal oversight of the methods used to deem medical marijuana necessary, that registrants often are similar to, if not the same as, recreational users (2,3). We attempted to mitigate this limitation by also using the number of medical marijuana dispensaries per county and obtained the same results. The number of dispensaries is also an imperfect by-proxy measure, as it may be more related to access than use. However, given the difficulty of an accurate measure of the true number of medical marijuana users, we had to use imperfect markers. Our results were the same with both by proxy measures of use. We were also unable to control for psychiatric comorbidities including substance use, as this information is not available in public records. Additionally, the number of recorded suicides suffers limitations inherent to retrospective analysis of records. It is likely not an accurate record of the total suicides committed secondary to misclassification of cause of death. However, it is the most accurate record available. This study attempted to draw correlations between numbers of people on the medical marijuana registry as a proxy measure of marijuana use and completed suicides. No such correlation was observed after controlling for confounders. At face value, this may seem somewhat reassuring given the presumed increase in marijuana use with its recent legalization. However, several prior studies have shown positive associations between suicidal ideations, attempts and marijuana use. Given limitations in data sources, a prospective design may be needed to better quantify this risk in light of the recent legalization of the recreational use of marijuana in Colorado.
Correlations between medical marijuana and suicide
Table 5. Pearson Correlation Coefficients between suicide deaths and mean county elevation. Correlation between suicide deaths and mean county elevation Pearson correlation Unadjusted Adjusted (partial)
log10(Suicide deaths) Mean county elevation log10(Suicide deaths) Mean county elevation Partial: log10(MMJ registrants) log10(Unemployment) Urban county (0/1)
0.36 (p ¼ 0.04) 0.14 (p ¼ 0.50)
0.15 (p ¼ 0.45) 0.03 (p ¼ 0.90)
0.45 (p ¼ 0.01) 0.08 (p ¼ 0.68)
0.50 (p ¼ 0.004) 0.23 (p ¼ 0.23)
0.37 (p ¼ 0.04) 0.08 (p ¼ 0.68)
0.35 (p ¼ 0.04) 0.09 (p ¼ 0.63)
0.26 (p ¼ 0.13) 0.09 (p ¼ 0.62)
Correlation between marijuana registrants and county elevation (maximum and mean) Pearson correlation
log10(MMJ registrants) Maximum county elevation log10(MMJ registrants) Mean county elevation
0.00 (p ¼ 0.99) 0.11 (p ¼ 0.48)
0.00 (p ¼ 0.99) 0.16 (p ¼ 0.31)
0.05 (p ¼ 0.76) 0.03 (p ¼ 0.84)
0.14 (p ¼ 0.32) 0.01 (p ¼ 0.97)
0.18 (p ¼ 0.16) 0.06 (p ¼ 0.62)
0.20 (p ¼ 0.11) 0.04 (p ¼ 0.77)
0.24 (p ¼ 0.06) 0.06 (p ¼ 0.62)
MMJ, Medical marijuana.
Acknowledgements The authors thank the Colorado Department of Public Health and Environment (CDPHE) for providing additional data.
Declaration of interest The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this paper.
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Does the legalization of medical marijuana increase completed suicide?
Suicide is among the 10 most common causes of death in the United States. Researchers have identified a number of factors associated with completed su...