European Psychiatry 30 (2015) 469–473

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Original article

Age, sex and personality in early cannabis use A. Muro i Rodrı´guez * Department of Clinical and Health Psychology, Universitat Auto`noma de Barcelona, Catalonia, Spain

A R T I C L E I N F O

A B S T R A C T

Article history: Received 12 January 2015 Received in revised form 5 February 2015 Accepted 11 February 2015 Available online 6 March 2015

Previous studies analysing personality and cannabis use in adult samples suggest that cannabis users show significant higher levels of impulsivity, sensation seeking and schizotypy. However, there are few studies exploring this relationship in adolescence using psychobiological models of personality. Given the relevance of identifying individual differences that lead adolescents to early cannabis use to prevent future health problems, the present study aimed to explore the relationship between age, sex, personality and early cannabis use using a psychobiological model of personality in a sample of 415 students (51.8% boys) from 12 to 18 years. Chi2 tests showed significant higher prevalence of cannabis use in boys and in the group aged 15–18 years. Multiple analysis of variance showed significant higher scores in psychoticism, sensation seeking and in all its subscales in cannabis users group, while an interaction with age was found for extraversion and neuroticism: cannabis users scored higher than nonusers in the youngest group (12–14 years) but lower in the oldest group in both dimensions. Finally, regression analysis showed that narrower traits of sensation seeking (experience seeking and disinhibition) were the most associated to early cannabis use. Results are discussed in terms of early cannabis users’ personality profiles and in terms of the self-medication theory. ß 2015 Elsevier Masson SAS. All rights reserved.

Keywords: Adolescent psychiatry Cannabis Personality

1. Introduction Cannabis is the most widely illegal recreational drug consumed in the world, with adolescents from 15 years old and young adults showing the highest consumption rates, increasing the prevalence of consumption up to 28% in European countries such as Spain [14,15]. Since the 1990s there has been a significant increase in the consumption of cannabis between general and school population in many countries of the European Union, but recently, a decline tendency has been detected. Nevertheless, the mean age for the initiation of cannabis use is around 14 years, situating it as the illegal drug that starts being consumed earlier than any other illegal substance in developed countries, and with boys showing a higher prevalence of consumption than girls’. However, although prevalence of cannabis use in adolescence is high, the large majority of adolescents will phase out cannabis use before it becomes problematic, and the percentage of adolescents who meet the criteria for long-term substance abuse is significantly lower [15,2,4]. Nevertheless, the negative impact that this substance might have on adolescents’ academic and social functioning, as well as on future mental and physical health, is significant and it is

* Tel.: +34 93 581 4452. E-mail address: [email protected]. http://dx.doi.org/10.1016/j.eurpsy.2015.02.008 0924-9338/ß 2015 Elsevier Masson SAS. All rights reserved.

increasing sanitary costs for western societies [14,21,22]. It is well established that frequent cannabis use exacerbates the expression of schizotypal symptomatology and a greater incidence of depression and anxiety in early adulthood is found [25,23,7,32] when its use begins in early adolescence [3,6,31]. Teenage is a significant period of brain development and behavioural maturation during which the corresponding changes in neuroplasticity places the adolescent brain at a particular risk to environmental factors such as drug exposure; using cannabis in this period increases the future risk of using other illicit drugs later in life, a phenomenon known as the gateway hypothesis [22]. However, it is also worth noting that a general increase in exploratory and social behaviours is also characteristic of this ontogenetic period [26,27,29], and not all individuals will be lead to abuse or to the intake of other addictive substances. And, although there are other factors that might lead to early cannabis use, such as cultural or familiar background, it is suggested that there is a genetical vulnerability [2,22,1,9] with reward-system based personality traits being their most powerful predictors [20,24,8,17,5,13]. Previous studies show that impulsivity and sensation seeking are the traits most associated to early cannabis use while anxiety and schizotypy are most related with a more persistent and heavy use through time. Schizotypy is a continuum of personality characteristics and experiences ranging from normal dissociative, imaginative states to more extreme states related to

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A. Muro i Rodrı´guez / European Psychiatry 30 (2015) 469–473

psychosis and in particular, schizophrenia [12]. It is defined by four factors including:  unusual experiences;  cognitive disorganization;  a tendency to introverted, emotionally flat and asocial behaviour;  and impulsive non-conformity, particularly with regard to rules and social conventions. Schizotypy is also associated to the extreme upper end of the eysenckian ‘psychoticism’ dimension of normal personality [11,16], a dimension regarded as a component of antisocial behaviour with associated impulsiveness, non-conformity and mood-related disinhibition, it is rather related with narrower symptoms of psychopathy and with the negative aspects of schizotypy [12]. Self-medication theories suggest that cannabis intake would act as a self-medication that helps individuals modulate specific outcomes of their extreme behaviours and personality [9,8,17,5]. For instance, cannabis would have a relaxing effect for those who express impulsive tendencies, and would facilitate the reduction of anxiety in social situations [8]. It is also suggested that sex might be a potential confound to studies of personality and cannabis use, since males are more likely to use cannabis and they also score significantly higher on impulsivity, sensation seeking and on the negative aspects of schizotypy. And although age of initiation has been identified as a significant predictor in the relationship between early cannabis use and future mental disorders, it has rarely been considered in the studies analysing normal personality and cannabis use in adolescence [20,24,8]. Furthermore, the role of personality traits under a dispositional approach in early cannabis use, and how certain combinations of traits increase the risk of early cannabis use in adolescence have been explored relatively few. Accordingly, the present study aims to identify, from a dispositional-psychobiological theoretical frame, those personality traits which are most related to early cannabis use, using Eysenck’s and Zuckerman’s personality models, in a non-clinical sample of Spanish adolescents, controlling for age and sex. Following the literature, it is hypothesised that (1) the prevalence of use would be higher in boys of increasing age from 12 to 18 years old, and (2) early cannabis use would be associated with adolescents showing higher scores in sensation seeking, neuroticism and psychoticism, which includes traits of impulsiveness and non-conformity. Finally, it is expected that (3) sex and age differences would be related with personality profiles of early cannabis users. 2. Method 2.1. Participants An initial sample of 486 students from four public high schools from the province of Barcelona participated in this study. Only those participants who answered completely all the questionnaires and who did not show social desirability were included in the data analyses. Social desirability was measured through the ‘‘Lie’’ scale included in the J-EPQ [16], and the 5% of subjects with the lowest scores in this scale were rejected from the analyses. The final sample (n = 415) consisted of 215 boys (51.8%) and 200 girls, ranging from 12 to 18 yrs old (mean = 14.76; SD = 1.75). 2.2. Measures To assess personality two questionnaires were administered:  the Spanish version of the Junior Eysenck Personality Questionnaire (J-EPQ) [16]: it extends personality assessment to children

and adolescents, measuring the same three major dimensions of personality as the adult version through 81 dichotomous items. The Neuroticism (N) scale consists in 23 items assessing levels of negative affect such as depression and anxiety. The internal consistency of the N scale for the present sample was .77. The Extraversion (E) scale consists in 24 items, which assess being outgoing, talkative, high on positive affect (feeling good), and in need of external stimulation. The internal consistency of the E scale for the present sample was .83. The Psychoticism (P) scale or ‘‘tough mindedness’’ is associated with egocentrism, aggressive and no-empathic behaviours through 18 items. The internal consistency of the P scale for the present sample was .82.  the Spanish version of the Junior Sensation Seeking Scale (J-SSS) [28]: it is an adaptation for adolescents of the Sensation Seeking Scale [35]. Sensation seeking (SS) is defined as ‘‘the seeking of varied, novel, complex, and intense sensations and experiences, and the willingness to take physical, social, legal, and financial risks for the sake of such experience’’ [33]. The scale contains 40 dichotomous items, with scores ranging from 0 to 40 (highest sensation seeking score). The internal consistency of the J-SSS scale for the present sample was .86 and it includes 4 subscales assessing: Thrill and Adventure Seeking (TAS), Experience Seeking (ES), Disinhibition (Dis), and Boredom Susceptibility (BS). The TAS subscale contains items expressing a desire to engage in sports or other physically risky activities that provide unusual sensations of speed or defiance of gravity, such as parachuting, scuba diving, or skiing. The ES subscale encompasses items measuring the seeking of novel sensations and experiences through the mind and senses, travelling, or being unconventional. The Dis subscale contains items describing seeking sensations through social activities such as parties, social drinking, and sex. Finally, the BS subscale measures intolerance for repetitive experiences of any kind, including routine work and boring people.

To assess early cannabis of use, in line with previous research to explore cannabis use [7,6], participants were asked ‘‘Have you smoked cannabis during the last year?’’ Participants who answered ‘‘yes’’ (18.3%) were categorised as users and participants who answered ‘‘no’’ (81.7%) were categorised as non-users. 2.3. Procedure A cross-sectional design was established and the researcher contacted four randomised high schools in Barcelona province (Catalunya) and asked for their collaboration. Questionnaires were administered during school sessions by the researcher and her assistants and participants completed the questionnaires anonymously in classroom settings. Parents were informed and gave consent prior to participant’s inclusion in this study. All students participated voluntarily and did not receive any academic or economic reward for their collaboration. The Ethical Committee of the university and the high schools’ management teams approved the protocol. 2.4. Statistical Analyses Means and standard errors of the means were computed for the J-SSS, J-EPQ scales and for age. Age was categorised into 2 age groups [30]: from 12 to 14 years old and from 15 to 18 years old. Prevalence of cannabis use and Chi2 tests were computed to contrast distributions by sex and age groups. Cronbach’s alphas were also calculated to test internal scores consistencies for the JSSS and for the J-EPQ. Pearson correlations were computed between age, J-SSS, and J-EPQ. A multivariate analysis of variance

Table 2 Pearson’s correlations among J-EPQ scales and J-SSS subscales and total scale. Thrill and Experience Disinhibition Boredom J-SSS adventure seeking susceptibility seeking J-EPQ Neuroticism .040 Extraversion .116* Psychoticism .000

.010 .143** .184**

.112 .110* .167**

.186** .147** .023

.112 .002 .129**

Notes: J-SSS = Junior Sensation Seeking Scale. *P < .05, **P < .01, two-tailed.

4.09 4.15 4.50 4.88 3.77 3.62 5.04

SE M SE

.125 .201 .271 .207 .267 .153 .301 4.22 5.16 5.03 4.94 5.25 3.82 6.37

M SE

.107 .165 .222 .170 .218 .125 .246 4.98 5.93 5.92 5.39 6.46 4.92 6.92

M SE

.149 .251 .338 .259 .333 .191 .376 6.48 7.27 7.03 7.12 7.18 6.23 8.07

M SE

.433 .654 .880 .673 .866 .497 .977 26.46 30.29 30.12 30.09 30.32 25.74 34.67

M SE

.205 .333 .448 .343 .441 .253 .498 5.15 7.22 5.58 4.42 8.39 5.56 7.25

M SE

.241 .393 .529 .404 .521 .299 .587

Experience seeking Thrill and adventure seeking Sensation seeking Psychoticism

M

% n % n % n % n % Cannabis use n No 339 81.70 168 40.48 171 41.20 176 42.41 163 39.28 Yes 76 18.31 47 11.33 29 6.99 14 3.37 62 14.94

16.35 14.99 15.71 17.62 13.08 15.75 14.95

15–18 (n = 225)

SE

12–14 (n = 190)

.206 .366 .493 .377 .485 .279 .547

Girls (n = 215)

M

Boys (n = 200)

Extraversion

Age

Sex Total sample (n = 415)

Neuroticism

Table 1 Prevalence of cannabis use by sex and age groups.

Table 3 Means and standard errors for the J-EPQ and J-SSS scales by sex, age and cannabis use groups.

The prevalence of cannabis use in the total sample was 18.3%; prevalence of use by sex and age groups are reported in Table 1. Statistically significant differences were found among prevalence of cannabis use on sex, with a higher prevalence in boys (x2 = 3.752.; P = .05) and in the age group from 15 to 18 years old (x2 = 17.28; P < .000). Mean age (15.7 yrs) was also significantly higher in the group of cannabis users when compared to non-users (14.5 yrs) (F = 33.74; P < .000). Significant correlations were found between age and EPQ’s E (r = .420), and P (r = .400) and with J-SSS’s ES (r = .378) and Dis (r = .189). Table 2 reports Pearson’s correlations among J-EPQ scales and J-SSS scales and subscales. MANOVA results (see Table 3) showed that boys obtained significantly higher scores than girls on P (F = 8.65; p = .003; hp2 = .023; observed power = .835). Regarding age, the youngest group scored significantly higher in N (F = 7.72; P = .006; hp2 = .020; observed power = .791), E (F = 47.45; P > 001; hp2 = .113; observed power = 1.00) and BS (F = 10.62; P = .001; hp2 = .028; observed power = .902), while the oldest group obtained significantly higher results in P (F = 50.49; P > .001; hp2 = .120; observed power = 1.00) and ES (F = 15,11; P > .001; hp2 = 0.39; observed power = .972). MANOVA also showed significant differences between cannabis users in P (F = 9.16; P = .003; hp2 = .024; observed power = .855) and in J-SSS total scale (F = 66.30; P > .001; hp2 = .152; observed power = 1.00) and in all its subscales, with significant higher scores in the users group as reported in Table 2. An interaction was found between cannabis users and age in N (F = 3.89; P = .049; hp2 = .010; observed power = .504): scores of the youngest cannabis users (mean = 13.00; sd = 3.90) were higher than the scores of the youngest non-users (mean = 11.43; sd = 4.22). The opposite pattern

11.25 10.99 11.68 12.19 10.49 11.16 11.52

3. Results

Total sample Boys Girls Age 12–14 Age 15–18 Non-users Users

Disinhibition

Boredom susceptibility

(MANOVA) considering the total score of the J-SSS and the total scores of J-EPQ scales (N, E, P) as dependent variables was performed taking cannabis use (users–non-users), sex and age group as factors. Partial eta-square (hp2) and observed power were also calculated. Finally, two binary logistic regression analyses were performed to describe the best predictors (age, sex, personality) of early cannabis use during the last year (yes-no): the first with broad personality scales and the second with narrower personality traits of J-SSS. Statistical tests were bilateral with Type I error set at 5%.

471 .119 .203 .273 .209 .269 .154 .303

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was observed in the oldest group aged 15–18: users’ scores (mean = 9.76; sd = 4.23) were lower than non-users’ scores (mean = 10.89; sd = 4.09). Results also show an interaction between age and cannabis use in E (F = 4.86; P = .028; hp2 = .013; observed power = .594): the youngest cannabis users scored higher (mean = 17.91; sd = 3.40) than non-users (mean = 17.27; sd = 3.70), while scores of the oldest cannabis users (mean = 11.41; sd = 7.08) were lower than non-users (mean = 14.15; sd = 5.56). Finally, a logistic binary regression analysis was performed for predicting the onset of cannabis use. First, sex, age and broad personality scales (N, E, P, SS) were considered as independent variables and a stepwise procedure was carried out to select the most significant predictors of cannabis use. In a second analysis, only personality subscales of the J-SSS were included. Results of the two analyses are summarized in Table 4. The best broad predictors associated with cannabis use were age, P and SS, with the three variables accounting for 30% of the total variance. However, when the narrower subscales of the JSSS were analysed separately together with age and sex, ES and Dis emerged as better predictors, explaining only both of them the 36% of cannabis use variance. 4. Discussion The present study analysing the relationship between personality and early cannabis use suggests that the prevalence of use is lower than the ones reported in previous studies in adolescent samples [14,15], confirming a decreasing tendency of early cannabis use in European countries such as Spain. Results also show that age is a good predictor in early cannabis use during adolescence, suggesting that adolescents older than 15 years are at higher risk for the onset of cannabis use. Moreover, since age, P, SS, ES and Dis subscales correlate positively, results reinforce the hypothesis that pubertal and behavioural changes that occur around this age would lead individuals to an increase of impulsive and exploratory behaviours that, in turn, might increase their exposure probabilities to high-risk situations such as substance use [26,27,29]. Results also confirm that the prevalence of boys using cannabis is significantly higher than girls’ [14,15,24,8], suggesting that sex differences have a significant relationship with cannabis use. Regarding personality, in line with previous studies [20,24,1,9,8,17,5], the present results show that, on the one hand, sensation seeking is the trait most related with early cannabis use, followed by psychoticism to a lesser degree. Both sensation seeking and psychoticism – which includes impulsivity trait in its hierarchical structure – have biological underpinnings rooted in testosterone levels [16,34], with higher levels of testosterone associated with higher levels of psychoticism and sensation seeking. Results regarding sensation seeking are as expected given the exploratory nature of initial cannabis use and that experimenting with substances can be seen as a highly novel and arousing experience. More specifically, narrower correlates of sensation seeking, such as experience seeking and disinhibition, have been found to be much more associated to cannabis use than age, sensation seeking and psychoticism together. According to neurobiological theories, early cannabis use could be partially explained by a two-factor model including sensation seeking and impulsivity or

disinhibiton, both traits related to increased dopaminergic activity in the reward system [24,33,34]. Furthermore, results regarding psychoticism – also related with reward sensitivity and testosterone levels – also suggest that early cannabis use might be associated to antisocial characteristics, as well as to negative aspects of schizotypal spectrum disorders [25,23,7,32,3,6,31]. Although psychoticism is a broad normal personality dimension whose upper end predisposes individuals to psychotic like experiences in a varying degree [16], some studies suggest that it is not a heightened risk for psychosis [12,11] and it is rather associated to symptoms of antisocial, schizotypal and borderline personality disorders [3,10]. On the other hand, although an overall decline through age in N and E was observed in users and non-users, the decrease in both personality dimensions was significantly higher in the cannabis users group. Accordingly, results suggest that the personality profiles of cannabis users are different depending on their age group, but are independent of sex: in the youngest group, cannabis users show higher levels in neuroticism and extraversion than non-users, while in the oldest group, cannabis users are more introverted and emotionally stable than non-users. Therefore, a question arises regarding whether there are two different personality profiles of cannabis users depending on age in the adolescence period, or if this difference might be associated to the effects of the substance itself during repeated use in adolescence by significantly decreasing their means of extraversion and neuroticism as cannabis users grow older. According to the psychobiological personality theory [16,34] and the self-medication theory [9,8,17,5,19,18], it is suggested that cannabinoids would be related with the activation thresholds of the limbic and sympathetic nervous systems, down-regulating neurotic outcomes related to worries, anxieties and irritating emotional feelings. Moreover, cannabis would also influence the activation thresholds and arousal needs of the Ascending Reticular Activation System (ARAS) related with extraversion [16] through the down regulation of the hypothalamic-pituitary-gonadal activity. Cannabinoids would also be associated to testosterone-based behavioural responses related with psychoticism and sensation seeking levels by down-regulating aggressive, impulsive and exploratory behaviours [5,18] during pubertal maturation. Nevertheless, the present study has several limitations and results should be interpreted with caution. First, the present study was cross-sectional. Hence, the implications of cannabis in the biological mechanisms of personality change could not be properly tested. Second, the data of the present sample was obtained from students of public Spanish high schools. Therefore, conclusions of this study may not generalize to other samples with different socio-demographic characteristics. Furthermore, other variables such as familiar or cultural background have not been included to control for their interactions with personality [20,24]. Finally, the measurement of cannabis use in the present study was dichotomous and categorical, and it might not reflect with precision the dimensionality of cannabis use [15]. For these reasons, future studies should use longitudinal designs in order to disentangle what personality traits discriminate recreational and sporadical users from problematic cannabis users, as well as to analyse the effects that the substance might have in the psychobiological

Table 4 Logistic Regression Analyses of age and personality scales as predictors of cannabis use.

Cannabis use

Predictors

Beta

Wald

Sig.

IC

R2

Age Psychoticism Sensation seeking ES Dis

.770 .088 .132 .412 .330

5.70 6.08 41.83 18.67 17.76

.017 .014 .000 .000 .000

.246–.871 1.018–1.172 1.096–1.187 1.204–1.770 1.150–1.574

.298 .364

A. Muro i Rodrı´guez / European Psychiatry 30 (2015) 469–473

underpinnings of personality change [22,20,9,8,17]. Future studies should also include a sample with a wider range of sociodemographic characteristics and assess other variables regarding, social, familiar and cultural background. Finally, the use of valid and reliable dimensional measures of cannabis use such as those recommended by the European Monitoring Centre for Drugs and Drug Addiction [15] is also encouraged for future studies. Contributions of the present study might help to facilitate the identification of personality traits involved in early cannabis use, an essential key point for prevention programs and interventions targeted at the promotion of adolescents’ well-being and oriented to prevent mental health problems later in adulthood. Disclosure of interest The authors declare that they have no conflicts of interest concerning this article. Acknowledgements The author would like to thank Noemı´ Valero, Elisabeth Martı´, Pablo Sa´nchez, Sara Marin and Iolao Mir for their assistance in recruiting the sample and to Prof. Montserrat Goma` i Freixanet her kind assessment. References [1] Agrawal A, Lynskey MT. Candidate genes for cannabis use disorders: findings, challenges and directions. Addiction 2009;104(4):518–32. [2] Agrawal A, Lynskey MT, Bucholz KK, Kapoor M, Almasy L, Dick DM, et al. DSM-5 cannabis use disorder: A phenotypic and genomic perspective. Drug Alcohol Depend 2014;134:362–9. [3] Anglin DM, Corcoran CM, Brown AS, Chen H, Lighty Q, Brook JS, et al. Early cannabis use and schizotypal personality disorder symptoms from adolescence to middle adulthood. Schizophr Res 2012;137(1–3):45–9. [4] American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders (DSM5), 5th ed. Madrid: Editorial Me´dica Panamericana, 2014. [5] Arendt M, Rosenberg R, Fjordback L, Brandholdt J, Foldager L, Sher L, et al. Testing the self-medication hypothesis of depression and aggression in cannabis-dependent subjects. Psychol Med 2007;37(7):935–45. [6] Arseneault L, Cannon M, Poulton R, Murray R, Caspi A, Moffitt TE. Cannabis use in adolescence and risk for adult psychosis: longitudinal prospective study. BMJ 2002;325(7374):1212–3. [7] Bailey E, Swallow BL. The relationship between cannabis use and schizotypal symptoms. Europ Psy 2004;19:113–4. [8] Barkus E. Personality cannabis use. Adv Schizo Clinical Psy 2008;3(3):84–9. [9] Casas M. Self-medication and addictions. In: Adan A, Vilanou C, editors. Substance abuse treatment. Barcelona: Marge Me´dica Books; 2011. p. 51–7. [10] Chabrol H, Melioli T, Goutaudier N. Association between personality disorders traits and problematic cannabis use in adolescents. Subst Use Misuse 2014. http://dx.doi.org/10.3109/10826084.2014.984851. [11] Chapman JP, Chapman LJ, Kwapil TR. Does the Eysenck Psychoticism Scale predict psychosis: a ten-year longitudinal study. Pers Indiv Differ 1994;17(3): 369–75. [12] Claridge G, McCreery C, Mason O, Bentall R, Boyle G, Slade P, et al. The factor structure of ‘schizotypal’ traits: A large replication study. Brit J Clin Psychol 1995;35:103–15.

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Age, sex and personality in early cannabis use.

Previous studies analysing personality and cannabis use in adult samples suggest that cannabis users show significant higher levels of impulsivity, se...
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