Motives for cannabis use as a moderator variable of distress among young adults

Motives for cannabis use as a moderator variable of distress among young adults

Addictive Behaviors 32 (2007) 1537 – 1545 Motives for cannabis use as a moderator variable of distress among young adults Jeannette Brodbeck a,⁎, Mon...

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Addictive Behaviors 32 (2007) 1537 – 1545

Motives for cannabis use as a moderator variable of distress among young adults Jeannette Brodbeck a,⁎, Monika Matter a , Julie Page b , Franz Moggi a a

University of Berne, University Hospital of Clinical Psychiatry Berne, Bolligenstrasse 111, CH-3000 Berne 60, Switzerland b Zürich University of Applied Sciences, School of Health Professions, Bankstrasse 4, CH-8400 Winterthur, Switzerland

Abstract This study examined the moderating effect of social and coping motives on distress among young cannabis-using adults. A random sample of 2031 young Swiss adults was interviewed by means of a computer-assisted telephone interview. Cannabis users showed more distress, less positive health behaviour and higher hedonism compared to nonusers. Taking motive for use as a moderator variable into consideration, it became evident that only cannabis users with coping motives showed lower mental health, more symptoms of psychopathology, more psychosocial distress and more life events than non-users. Young adults with social motives for use on the other hand did not differ from non-users in terms of distress. These differences between cannabis users with social and those with coping motives remained stable over two years. In both subgroups, participants with regular cannabis use at baseline did not increase distress nor did participants with higher distress at baseline increase the frequency of their cannabis use. Our results suggest that secondary prevention for cannabis users should target especially young adults with coping motives for use. © 2006 Elsevier Ltd. All rights reserved. Keywords: Cannabis; Distress; Young adults; Motives; Moderator

1. Introduction Cannabis use is widespread among adolescents and young adults. In the majority of cases, cannabis use is age-limited and given up once adulthood is reached, with new professional responsibilities, marriage or parenthood. Many emerging adults even with excessive cannabis use do not develop long-term drug⁎ Corresponding author. Present address: University of Berne, Department of Psychology, Gesellschaftsstrasse 49, CH-3012 Berne, Switzerland. Tel.: +41 31 631 40 23; fax: +41 31 631 41 55. E-mail addresses: [email protected] (J. Brodbeck), [email protected] (M. Matter), [email protected] (J. Page), [email protected] (F. Moggi). 0306-4603/$ - see front matter © 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.addbeh.2006.11.012

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related problems (Arnett, 2005; von Sydow et al., 2001) and many studies did not find any association between less frequent cannabis use and mental disorders or other drug-related problems (Degenhardt, Hall, & Lynskey, 2003; Degenhardt, Hall, Lynskey, Coffey, & Patton, 2004; Patton et al., 2002; Poulton, Moffitt, Harrington, Milne, & Caspi, 2001). However, numerous publications show that addicted high-dose cannabis use over several years significantly increases the risk of psychosis (Andreasson, Allebeck, Engstrom, & Rydberg, 1987; Van Os, Hanssen, Bijl, & Vollebergh, 2002; Verdoux, 2004; Zammit, Allebeck, Andreasson, Lundberg, & Lewis, 2002), depression or anxiety disorder (Bovasso, 2001; Degenhardt et al., 2003, 2004; Patton et al., 2002). The specific mechanisms underlying these associations need to be explored further and may differ in different age groups. Not only regular high-dose cannabis use but also infrequent, recreational cannabis use was found to be associated with psychological problems. Fergusson, Horwood, and Swain-Campbell (2002) revealed an association between cannabis use and other illegal substance use, delinquency, depression and suicidal behaviour and a frequency of use that is less than once a month. Degenhardt, Hall, and Lynskey (2001) found an association between a higher rate of anxiety and affective disorders and a frequency of use of once every second month. Brodbeck, Matter, and Moggi (2005) found that in a representative sample of 5448 Swiss adolescents aged 16–18, cannabis use of once a month was associated with higher psychosocial distress, more physical complaints, less positive attitude towards life, more smoking and more regular alcohol consumption. Cannabis use of 1–2 times per week was related to higher scores of depression compared to no or less frequent use. It is important to identify subgroups of young cannabis users who do not show adverse effects of cannabis use and subgroups, who are at greater risk to develop harmful effects on mental health or health behaviour at an early stage in order to understand the dynamic of cannabis use and to design effective preventive intervention. Established risk factors for problematic cannabis use associated with psychosocial harm are higher frequency of use, lower onset age, lower onset age of regular use, longer length of use, mental disorders (von Sydow et al., 2001) and fewer psychosocial resources (Huesler, Werlen, & Plancherel, 2004). However, at present it cannot be said with certainty which psychological characteristics of cannabis users, which pattern of infrequent use, or which interaction between these factors correlate with a nonproblematic use of cannabis and do not bear a risk of future drug-related problems. Analysing the reasons for cannabis use however, may be an important step towards understanding the association between cannabis use and its adverse effects and thus towards tailoring effective interventions to achieve behaviour changes (Simons, Correia, Carey, & Borsari, 1998). Furthermore, different functional roles of and reasons for cannabis use may be instrumental in shaping different patterns and different contexts of use, which in turn may be associated with a different level of drug-related problem. As established in this and many other studies the main reasons for use are the enhancement of positive affects, the expansion of experimental awareness, social conformity, social cohesion motives, and the reduction of negative affect (Newcomb, Chou, Bentler, & Huba, 1988; Simons et al., 1998). Age-specific reasons for cannabis use among emerging adults are identity exploration, encouragement by substanceusing friends to foster the integration in a peer group, or to relieve feelings of distress caused by identity confusions and age-related instability (Arnett, 2005; Silbereisen & Reese, 2001). Simons et al. (1998) found that social motives for cannabis use and non-coping motives were a significant predictor of negative consequences of cannabis use. Chabrol, Duconge, Casas, Roura, and Carey (2005) concluded in a cross-sectional study that the motives for use were more important than psychopathology in predicting cannabis use in adolescents and young adults.

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To provide a better understanding of the factors that discriminate problematic and non-problematic cannabis use, the present study focuses on the motives for cannabis use and their association with mental health and psychosocial distress. We will analyse the development of psychopathology and psychosocial distress over two years among young cannabis users with coping and social motives, who continued using cannabis. Additionally we include a higher frequency of use and a lower psychosocial adjustment at baseline as risk factors for problematic cannabis use. To our knowledge motives for cannabis use have not yet been analysed as moderator variables of mental health and psychosocial distress among cannabis users in a longitudinal non-clinical random sample. If the motive for use is a moderator variable of distress among cannabis users, we should two subgroups of cannabis users who differ in terms of mental health, psychopathology, psychosocial distress and life events. We tested the following hypotheses. 1) Cannabis users with social motives show a better mental health, lower psychopathology and psychosocial distress and less life events than participants with coping motives. 2) Cannabis users with social motive level of distress do not differ from non-using persons. 3) Cannabis-using young adults with higher distress scores at baseline increase their frequency of cannabis use over two years only when they use cannabis for coping reasons. 4) A higher frequency of cannabis use at baseline increases distress at follow-up only among cannabis users with coping motives. 2. Methods 2.1. Participants A random sample of 16 to 24-year-old urban Swiss men and women was selected based on the official registers of the Residents' Administration Offices of the Swiss cities of Basel, Berne, and Zurich. Data were collected by computer-assisted telephone interview (CATI) at baseline from January to July 2003 and in a two year follow-up investigation from February to May 2005. After excluding invalid telephone numbers, people with insufficient mastery of the German language, and individuals with serious health problems that precluded participation in the interview, we interviewed 2844 people at baseline. The response rate was 71%. The sample included 52% young women and 48% young men. Mean age was 20 years (SD = 2.46), with 38% of participants aged 16 to 18 years, 31% aged 19 to 21 years, and 31% aged 22 and 24 years. Most of the participants were in comprehensive secondary school or at university (37%), in professional training (26%), or employed (20%) at the time of the interview. In the follow-up survey, we successfully interviewed 2031 people. Interviewees who did not participate in the second investigation did not significantly differ from the participants of both investigations. The follow-up response rate was also 71%. 2.2. Measures (a) Substance use: The interviewees were asked how often they had consumed cannabis, alcohol, and alcohol to the point of drunkenness in the previous month (0 = never, 1 = 1–3 times a month, 2 = 1–2 times a week, 3 = 3–6 times a week, 4 = daily). They also reported whether they had used cannabis at all in the 12month period prior to the baseline investigation and in the 24-month period prior to the follow-up investigation. (b) Motives for cannabis use: We assessed motives for cannabis use on an 11-point scale (“I consume cannabis in the context of distress or problems”, “I consume cannabis because my friends also use

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cannabis”, “I consume cannabis out of curiosity” and “I consume cannabis for other reasons”, 0 = not at all, 10 = very much). (c) Mental health was assessed using the mental health scale of the Trier Personality Questionnaire (Becker, 1989). This scale defines mental health as good psychological functioning and includes the aspect of adequate coping with internal and external problems (20 items; Cronbach's alpha = .83; 0 = not at all to 4 = very much; higher scores indicate better psychological functioning). (d) Psychopathology was assessed with a short version of the SCL (9 items, Cronbach's alpha = .75, correlation with SCL-90-R (Franke, 1995): r = .93, 0 = not at all to 4 = very much). (e) Psychosocial distress (9 items, e.g., distress in school/job or distress with parents, Cronbach's alpha = .76, 0 = not at all 10 = very much). (f ) Life events such as major personal illness or injury; illness, injury or death of a friend or family member; changing residence; or breaking up with a girlfriend or boyfriend during the previous two years were assessed with 11 items (yes/no). (g) Health behaviour like balanced diet, enough sleep or importance of health was assessed with 7 items (0 = not at all to 10 = very much, Cronbach's alpha = .74). (h) Hedonism was assessed in accordance with the hedonism scale of the Trier Integrated Personality Inventory (Becker, 2003; 8 items; Cronbach's alpha = .72; 0 = in none of five cases to 5 = in five of five cases). Individuals with high hedonism scores often act impulsively, have a strong desire to experience pleasure, consume without inhibition, and readily give in to temptation. 2.3. Data analyses To determine the existence of subgroups among cannabis users, we built a dichotomous variable for mainly coping reasons (score coping N score social reasons) or mainly social reasons (score social reasons N score coping reasons). We included cannabis users who used cannabis at least once in a month prior to the baseline-interview as well as once in a month prior to the two-year follow-up. Non-users were defined as participants who never used cannabis prior to the last two years at follow-up. To compare cannabis users with non-users we computed t-tests for independent samples and Cohen's d as effect size for continuous variables and Pearson chi-square tests for nominal variables. We used Pearson's productmoment correlations to analyse univariate associations. To compare cannabis users with social and coping motives with control of the frequency of use and to analyse changes over time we computed the analyses of covariance (ANCOVAS) with frequency of cannabis use as a covariate. To test the hypothesis that cannabis-using young adults with coping or social motives with higher distress scores at baseline increase their frequency of cannabis use at follow-up, we computed tertils for all cannabis-using participants. We analysed the tertil with the highest level of psychopathology and psychosocial distress and lowest mental health and computed McNemar-Bowker tests separately for both subgroups. 3. Results 3.1. Comparison of cannabis users with non-cannabis-using young adults 19% of the participants (n = 374) consumed cannabis at least once a month prior to the baseline investigation as well as at least once a month prior to the follow-up interview. Compared to participants reporting no cannabis use (n = 1327), cannabis users showed a higher psychopathology, more life events

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and more psychosocial distress (Table 1). They had lower health behaviour and a higher indifference towards health as well as a higher hedonism. 3.2. Motives for use and differences between cannabis users with social and with coping motives at baseline 44% of cannabis users reported predominantly social reasons for use (n = 133), 39% cited predominantly coping reasons (n = 119); fewer young adults reported that both type of reasons were equally important (17%, n = 51). Only few participants indicated curiosity (17%), having fun or addiction (less than 10%) as their reasons for cannabis use. Social and coping reasons were independent and did not correlate (r = .04, p N .05). Both types of reasons were independent of age (social reasons: r = −.07, coping reasons: r = −.09, p N .05) or gender (social reasons: r = −.04, coping reasons: r = −.02, p N .05). The average duration of use for both groups was six years (M = 6.55, SD = 2.50, vs. M = 6.10, SD = 2.60, t (240) = 1.36, p = .176). However, young adults with coping motives consumed cannabis more frequently than participants with social reasons for use (v2 (3, 252) = 16.97, p N .001). Therefore, we statistically controlled the frequency of cannabis use in the subsequent analyses. The hypothesis that participants who used cannabis for social reasons had at baseline a better mental health, lower psychopathology score, less psychosocial distress, and less critical life events compared to cannabis users with coping motives was confirmed. These differences were confirmed through the statistical control of the frequency of use and it could be concluded that they were not due to the higher frequency of cannabis use among participants with coping motives. As assumed, participants who used Table 1 Comparison of all cannabis users, cannabis users with coping motives, cannabis users with social motives and non-using participants with regard to mental health, psychopathology, psychosocial stress, health behaviour and hedonism at baseline 1

1a

1b

2

All cannabis users (n = 374)

Coping motives (n = 119)

Social motives (n = 133)

No cannabis use (n = 1327)

M, SD

M, SD

M, SD

M, SD

1 vs. 2

1a vs. 1b

1a vs. 2

1b vs. 2

t, d

F, d

t, d

t, d

− 2.31⁎, .23 4.20⁎⁎⁎, .40 3.32⁎⁎, .32 6.68⁎⁎⁎, .70 − 3.91⁎⁎⁎, .38 3.79⁎⁎⁎, .38

0.18, .02

Mental health

3.23, 0.03

3.19, 0.27

3.26, 0.28

3.25, 0.30

− 1.29, .08

5.04⁎, .29

Psychopathology

1.00, 0.59

1.15, 0.64

0.89, 0.52

0.90, 0.64

2.38⁎, .14

Psychosocial stress Life events

3.57, 1.56

3.87, 1.57

3.38, 1.44

3.35, 1.62

2.27⁎, .13

2.35, 1.50

2.91, 1.66

2.08, 1.29

1.87, 1.29

Health behaviour

5.90, 1.58

5.74, 1.54

5.84, 1.52

6.33, 1.60

Hedonism

3.10, 0.72

3.04, 0.68

3.17, 0.67

2.76, 0.77

5.72⁎⁎⁎, .35 − 4.64⁎⁎⁎, .27 7.47⁎⁎⁎, .45

13.93⁎⁎⁎, .48 6.83⁎⁎, .34 16.92⁎⁎⁎, .53 0.38, .08

⁎p b . 05, ⁎⁎p b . 01, ⁎⁎⁎p b . 001. Group 1: frequency of use at least once a month. Control group 2: no cannabis use during the last two years.

5.41⁎, .30

−0.20, .02 0.19, .02 1.78, .16 −3.39⁎⁎⁎, .31 5.84⁎⁎⁎, .56

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cannabis for social reasons did not systematically differ from the group of non-cannabis-using participants in mental health, psychopathology, and psychosocial distress and life events. Cannabis users with coping motives however showed a lower mental health, higher psychopathology scores, more psychosocial distress, and more life events as non-users (Table 1). Cannabis users with coping motives reported more life events like death of a close family member or a friend, (26% vs. 18%, (v2 (1, 252) = 11.92, p b .001), injury or illness of a close family member or a friend (25% vs. 19%, (v2 (1, 252) = 8.67, p b .01), change in residence (22% vs. 17%, (v2 (1, 252) = 5.12, p b .05) or personal injury or illness (13% vs. 8%, (v2 (1, 252) = 5.32, p b . 05) compared to participants with social motives for use. Both, cannabis users with social motives and coping motives showed less positive health behaviour and were more indifferent towards health than non-users. Participants with social motives had higher hedonism scores compared to cannabis users with coping motives and compared to non-users. 3.3. Development of mental health, distress, health behaviour and hedonism over two years among cannabis users with social and coping motives Both subgroups of cannabis users did not change their mental health, distress, health behaviour and hedonism over two years. In contrast to our hypothesis, participants with coping reasons for use kept their higher level of distress and lower level of mental health and hedonism at follow-up and did not increase distress when consuming over two years. Also cannabis users with social reasons for use did not increase distress over two years. Thus, the baseline differences between cannabis users with coping and with social motives remained stable over two years (Table 2). 3.4. Frequency of use and higher distress at baseline as moderator variables The hypothesis that a higher frequency of cannabis use increases distress was not confirmed. Neither did we find changes in mental health, psychopathology and psychosocial distress among cannabis users Table 2 Development of stress among participants with continued cannabis use over two years (coping motives n = 103, social motives n = 97) with control of frequency of use

Mental health Psychopathology Psychosocial stress Health behaviour Hedonism

Coping motive

Social motive

F

F

F

M, SD t1

M, SD t1

(Time)

(Interaction)

M, SD t2

M, SD t2

(Between subject)

0.01

0.72

5.48⁎

1.85

0.24

23.20⁎⁎⁎

0.33

3.04

18.68⁎⁎⁎

3.02

0.01

0.28

0.98

0.42

6.42⁎

3.16 3.19 1.15 1.18 4.26 3.88 5.41 5.86 3.18 3.07

⁎p b . 05, ⁎⁎p b . 01, ⁎⁎⁎p b . 001.

0.33 0.26 0.64 0.64 1.57 1.61 1.48 1.42 0.64 0.68

3.27 3.25 0.78 0.86 3.26 3.27 5.51 5.90 3.29 3.22

0.29 0.28 0.55 0.53 1.43 1.44 1.55 1.44 0.63 0.68

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with coping motives (n = 55) and social motives (n = 44) at follow-up (t between −.34 and 1.08, p N .05) among cannabis users who consumed cannabis at least three times a week over two years. Furthermore, the hypothesis that cannabis users with lower mental health and higher psychopathology and psychosocial distress at baseline would increase the frequency of cannabis use over two years was not confirmed for both subgroups (McNemar-Bowker between 1.20 and 7.62, p N .05). Participants with social or coping motives for use and lower mental health, more psychopathology and higher distress at baseline did not change distress or their frequency of cannabis use. 4. Discussion Cannabis-using young adults showed higher psychopathology scores, more psychosocial distress and more life events than non-cannabis-using participants. Although the differences in psychopathology and psychosocial distress were small, the result was consistent with the finding that individuals who use cannabis show more social and psychological distress than non-users (Brodbeck et al., 2005; Degenhardt et al., 2001; Fergusson et al., 2002). Cannabis users reported less positive health behaviour and a higher indifference towards health and higher hedonism scores than non-cannabis-using young adults. However, the results of this study demonstrate that the motive for cannabis use is an important moderator of mental health, psychopathology, psychosocial distress and life events among cannabis-using young adults. Coping and social reasons for use discriminated two distinct subgroups of cannabis users who differed in all assessed distress-related variables. Only cannabis users with coping motives had a lower mental health, higher psychopathology scores, more psychosocial distress and more life events than non-cannabis-using young adults. Participants who used cannabis for social reasons were not more distressed than non-cannabis-using interviewees. Controversial results of former studies with regards to the association between mental health, distress and infrequent cannabis use (Degenhardt et al., 2004; Patton et al., 2002; Poulton et al., 2001) might partially be explained by the fact that motives for use were differently distributed in different samples and were not controlled as moderator variables in those studies. Coping motives and social motives did not correlate and differed clearly for 83% of the cannabis users. Motives were not correlated with age or gender, but cannabis users with coping motives had a higher frequency of use. Average duration of cannabis use in both groups was six years, thus social motives were not a characteristic of an early stage of cannabis use. Only cannabis users with coping motives had a lower mental health, higher psychopathology scores, more psychosocial distress and more life events than non-cannabis-using young adults. In contrast, Simons et al. (1998) found in a sample of 299 college students that social and non-coping motives were a predictor of cannabis-related problems. However, the authors assessed merely specific cannabis-related problems and not general mental health and psychosocial distress. Cannabis use as emotion-focusing coping (Westen, 1994) is often related to expectations that cannabis use alleviates general negative affects. Young adults with coping motives may also experience cannabis use as helpful to relieve negative affects and may perceive the effects of cannabis use as more beneficial than problematic. Social motives for use include social conformity and social cohesion motives and may be learnt from models in the peer group. Cannabis use may be adaptive behaviour in order to feel integrated in a peer group (Silbereisen & Reese, 2001). In our study, cannabis use with social motives, also with a high frequency of use and higher distress at baseline, did not seem to be associated with a lower mental health, higher psychopathology, and more psychosocial distress and life events. There are different explanations for this finding: cannabis use per se may not increase the risk of psychological or psychosocial distress. Cannabis use may lead to more

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distress, but cannabis users with social motives for use might be better integrated in a peer group and get more social support for coping with problems. Young adults who use cannabis without intrapersonal coping function may also abandon cannabis use easily as soon as they realize that cannabis starts having adverse effects and before more serious problems occur. In contrast distress and coping motives may complicate the cessation of cannabis use. Here, further longitudinal research is needed. The differences between cannabis users with coping and those with social motives for use remained stable over two years. In both subgroups, young adults with continued cannabis use over two years did not develop or increase psychosocial distress or increase frequency of use. Thus, cannabis use with social motives did not seem to be related to subsequent problems. Even participants with a high degree of distress at baseline did not systematically increase their frequency of use over the following two years, independently of their motives for use. Accordingly, a high frequency of use at baseline did not lead to an increase of the level of distress over two years. Thus, regular cannabis users who consume cannabis at least three times a week over two years did not develop a higher level of distress at follow-up and cannabis users with social reasons still did not differ from non-cannabis-using participants. Thus, our study could not replicate the finding that higher frequency of use, mental disorders and lower psychosocial resources (Huesler et al., 2004; von Sydow et al., 2001) are risk factors for an increased frequency of use and the development of psychosocial problems. This may be partially explained by the participants' age, which was a limiting factor in the study: most of the cannabis-using emerging adults already used cannabis at baseline with an average duration of use of six years. After that time, their frequency of use and level of distress seemed to be stable. Thus, it was not possible to analyse whether cannabis use with coping motives at onset was a reaction to distress or whether cannabis use led to a higher level of distress. Two particularly strong points of this study were the longitudinal design applied and the use of a random sample based on the official registers of the Residents' Administration Offices of three major cities in Switzerland. This meant that the sample was not limited to a clinical sample of adolescents or to young adults who were at school or university, and a higher generalisability was assured. However, future research should set the longitudinal studies earlier in the participants' life-span; this would also allow an analysis of antecedents of the cannabis use's onset and the temporal sequence of cannabis use and distress. The results of our study have significant implications for identifying high-risk young cannabis users. The approach that made this possible was that non-cannabis as a substance, the frequency of cannabis use or the duration of use were associated with lower mental health, more psychopathology, more psychosocial distress and more life events, but the personal characteristic of the consuming young adults, in particular their motives for use. Our results suggest that secondary prevention for cannabis users should target young adults with coping motives for use. Cannabis users with social motives do not seem to need interventions to prevent psychological or psychosocial distress or life events. Motives for use were assessed with two simple questions, which showed a highly discriminating effect with regards to mental health, psychopathology, and psychosocial distress and life events. This distinction, namely whether an emerging adult uses cannabis predominantly in the context of distress and problems or mainly for social reasons, appears to have clinical significance for the decision-making as far as the necessity of prevention and early intervention are concerned. Acknowledgements This research was funded by the Swiss National Science Foundation (Grant No. 3346-65580 and 3346C0-104080/1) and the Swiss Federal Office of Public Health (Grant No. 04.001846). The authors

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would like to thank Michael Roethlisberger, Simone Artho, Veronique Eicher, Nadja Razavi, Sabine Luedi and Eva Schuerch for their contributions during data collection and analyses. References Andreasson, S., Allebeck, P., Engstrom, A., & Rydberg, U. (1987). A longitudinal study of Swedish conscripts. Lancet, 2, 1483−1486. Arnett, J. J. (2005). The developmental context of substance use in emerging adulthood. Journal of Drug Issues, 35(2), 235−254. Becker, P. (1989). Der Trier Persönlichkeitsfragebogen TPF. [TPF, Trier Personality Questionnaire. Göttingen, Germany: Hogrefe. Becker, P. (2003). TIPI. Trierer Integriertes Persönlichkeitsinventar [TIPI, Trier Integrated Personality Inventory]. Göttingen, Germany: Hogrefe. Bovasso, G. B. (2001). Cannabis abuse as a risk factor for depressive symptoms. American Journal of Psychiatry, 158, 2033−2037. Brodbeck, J., Matter, M., & Moggi, F. (2005). Konsumhäufigkeit von Cannabis als Indikator für biopsychosoziale Belastungen bei Schweizer Jugendlichen [Biopsychosocial correlates of cannabis use among adolescents]. Zeitschrift für Klinische Psychologie, 34(3), 188−195. Chabrol, H., Duconge, E., Casas, C., Roura, C., & Carey, K. B. (2005). Relations between cannabis use and dependence, motives for cannabis use and anxious, depressive and borderline symptomatology. Addictive Behaviors, 30, 829−840. Degenhardt, L., Hall, W., & Lynskey, M. (2001). Alcohol, cannabis and tobacco use among Australians: A comparison of their associations with other drug use disorders, affective and anxiety disorders, and psychosis. Addiction, 96, 1603−1614. Degenhardt, L., Hall, W., & Lynskey, M. (2003). Exploring the association between cannabis use and depression. Addiction, 98, 1493−1504. Degenhardt, L., Hall, W., Lynskey, M., Coffey, C., & Patton, G. (2004). In D. Castle & R. Murray (Eds.), Marijuana and madness: psychiatry and neurobiology (pp. 54−74). New York: Cambridge University Press. Fergusson, D. M., Horwood, L. J., & Swain-Campbell, N. (2002). Cannabis use and psychosocial adjustment in adolescence and young adulthood. Addiction, 97, 1123−1135. Franke, G. H. (1995). SCL-90-R. Symptom-Checkliste von Derogatis. Weinheim: Beltz. Huesler, G., Werlen, E., & Plancherel, B. (2004). Der Einfluss psychosozialer Faktoren auf den Cannabiskonsum [The influence of psychosocial factors on cannabis consumption]. Suchtmedizin in Forschung und Praxis, 6, 221−235. Newcomb, M. D., Chou, C. -P., Bentler, P. M., & Huba, G. J. (1988). Cognitive motivations for drug use among adolescents: Longitudinal tests of gender differences and predictors of change in drug use. Journal of Counseling Psychology, 35, 426−438. Patton, G. C., Coffey, C., Carlin, J. B., Degenhardt, L., Lynskey, M., & Hall, W. (2002). Cannabis use and mental health in young people: Cohort study. British Medical Journal, 325, 1195−1198. Poulton, R., Moffitt, T. E., Harrington, H., Milne, B. J., & Caspi, A. (2001). Persistence and perceived consequences of cannabis use and dependence among young adults: Implications for policy. The New Zealand Medical Journal, 114, 544−547. Silbereisen, R. K., & Reese, A. (2001). Substanzgebrauch: Illegale Drogen und Alkohol [Substance use: Illegal drugs and alcohol]. In J. Raithel (Ed.), Risikoverhaltensweisen Jugendlicher: Formen, Erklärungen und Prävention [Adolescents' risktaking behavior] (pp. 131−154). Opladen, Germany: Leske and Budrich. Simons, J., Correia, C. J., Carey, K. B., & Borsari, B. E. (1998). Validating a five-factor marijuana motives measure: Relations with use, problems, and alcohol motives. Journal of Counseling Psychology, 45, 265−273. Van Os, J., Hanssen, M., Bijl, R. V., & Vollebergh, W. (2001). Prevalence of psychotic disorder and community level of psychotic symptoms: An urban–rural comparison. Archives of General Psychiatry, 58, 663−668. Verdoux, H. (2004). Cannabis and psychosis proneness. In D. Castle & R. Murray (Eds.), Marijuana and madness: psychiatry and neurobiology (pp. 75−88). New York: Cambridge University Press. von Sydow, K., Lieb, R., Pfister, H., Hofler, M., Sonntag, H., & Wittchen, H. U. (2001). The natural course of cannabis use, abuse and dependence over four years: A longitudinal community study of adolescents and young adults. Drug and Alcohol Dependence, 64, 347−361. Westen, D. (1994). Toward an integrative model of affect regulation: Applications to social–psychological research. Journal of Personality, 62, 641−667. Zammit, S., Allebeck, P., Andreasson, S., Lundberg, I., & Lewis, G. (2002). Self reported cannabis use as a risk factor for schizophrenia in Swedish conscripts of 1969: Historical cohort study. British Medical Journal, 325, 1199−1201.