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Background: A younger age at onset of use of a specific substance is a well-documented risk-factor for a substance use disorder (SUD) related to that specific substance. However, the cross-substance relationship between a younger age at onset of alcohol use (AU) and nicotine use (NU) and the risk of cannabis use disorders (CUD) in adolescence and early adulthood remains unclear. Aims: To identify the sequence of and latency between initial AU/NU and initial cannabis use (CU). To investigate whether younger age at AU- and NU-onset is associated with any and earlier CU-onset and a higher risk of transition from first CU to CUD, taking into account externalizing disorders (ED) and parental substance use disorders as putative influential factors. Methods: Prospective-longitudinal community study with N = 3021 subjects (baseline age 14–24) and up to four assessment waves over up to ten years with additional direct parental and family history information. Substance use and CUD were assessed with the DSM-IV/M-CIDI. Results: Most subjects with CU reported AU (99%) and NU (94%). Among users of both substances, 93% reported AU prior to CU (87% for NU). After adjustment for ED and parental substance use disorders younger age at AU-onset was associated with any CU. Younger age at NU-onset was associated with earlier CU initiation. Younger age at AU- and NU-onset was not associated with a higher risk of CUD. Conclusions: The cross-substance relevance of younger age at first AU and NU for the risk of CUD is limited to early CU involvement.

Le cannabis est la substance illicite la plus consommée à l’adolescence et ce, mondialement. Nous savons qu’un usage problématique de cannabis est susceptible d’entraîner une multitude de conséquences sur les plans physiques, psychologiques, sociaux et économiques. Or, les consommateurs constituent un groupe au profil hétérogène et n’expérimenteront pas tous des problèmes significatifs reliés à cet usage. Il s’avère donc important d’identifier les usagers à risque élevé de conséquences et de spécifier la nature de ces problèmes afin d’intervenir de façon efficace auprès de cette clientèle. Pourtant, bien que la littérature scientifique soulève l’idée que certains types de consommateurs présentent davantage de risques, l’état des connaissances ne révèle que peu d’informations de nature empirique qui permettraient de distinguer des autres usagers les profils d’adolescents davantage à risque. À cet effet, les typologies disponibles à ce jour sont généralement théoriques ou limitées aux études cliniques, font référence à des problèmes particuliers ou se basent sur des indicateurs spécifiques de la consommation tels que la fréquence d’usage. De plus, aucune étude jusqu’à maintenant n’est en mesure de nous pister quant aux types de problèmes associés plus spécifiquement à certains profils de consommation ni de préciser quels profils sont davantage représentés pour des conséquences données. Cette étude est basée sur les classes latentes de consommation découvertes dans l’étude de Fallu, Brière et Janosz (2014) à partir de plusieurs caractéristiques de consommation et comparées sur plusieurs prédicteurs et problèmes associés à la consommation. Son échantillon est constitué de 1618 élèves consommateurs de cannabis en secondaire 4. Cette étude examine quels sont les problèmes attribués et non-attribués les plus fréquents pour chacune des classes. Elle examine également quelles sont les classes les plus représentées pour différents problèmes attribués et non-attribués. Enfin, elle compare les résultats obtenus pour les problèmes attribués et non-attribués. La stratégie analytique employée a consisté à conduire des analyses descriptives, des analyses de Chi carrés ainsi que des analyses de variance univariée, parfois suivies d’une analyse post-hoc. Les résultats ont démontré que la classe d’appartenance peut prédire la survenue des différents problèmes que rencontrent les jeunes consommateurs, que certaines classes sont plus représentées pour certains problèmes et que les adolescents aux profils les plus lourds sont à risque de sous-estimer certains problèmes liés à leur consommation. L’une des principales découvertes concerne les deux classes précoces. Il semble que la classe des consommateurs modérés précoces présente un profil de problèmes davantage intériorisé et la classe des polyconsommateurs lourds précoces, davantage extériorisé. Les implications de ces résultats sont finalement discutées. / Cannabis is the most widely used illicit substance among adolescents worldwide. We know that cannabis misuse is likely to cause a variety of effects at physical, psychological, social and economic levels. However, consumers are a heterogeneous group and not all will experience significant problems associated with such use. It is therefore important to identify high-risk users and to specify the nature of these problems in order to intervene effectively with this clientele. Yet, although the scientific literature raises the idea that certain types of consumers are at higher risk, the current state of knowledge reveals little empirical information that would distinguish adolescents with higher risk profiles. To this end, the typologies available today are generally limited to theoretical or clinical studies, refer to specific problems, or are based on specific consumption indicators such as frequency of use. Furthermore, no study has yet been able to reveal the types of problems associated specifically with certain consumer profiles or to specify which profiles are more prone to various consequences. The present study is based on a latent class consumption model developed from several consumer characteristics found in the study by Fallu, Briere and Janosz (2014). They were compared with several predictors and problems associated with the consumption. The sample comes from within the context of evaluation of the New Approaches New Solutions (NANS) dropout prevention program, and consists of 1618 students who used cannabis in 10th grade. The subjects were annually evaluated from the 7th grade until the 11th. This study examines which attributed and non-attributed problems are most common for each class. It also examines which classes are most frequently assigned to different attributed and non-attributed problems. Finally, it compares the results obtained for the attributed and non-attributed problems. The analytical strategy used was to conduct descriptive analysis, chi-square analysis and univariate analysis of variance (ANOVA), sometimes followed by post-hoc tests when relevant. The results show that the class can predict the occurrence of various problems that young people face, that some classes are more represented for some problems, and that teenagers with heavier profiles are at risk of underestimating certain problems associated with their consumption. One of the main findings regarding the two early classes. It seems that early-moderate use students have a more internalized problems profile and those with early-heavy and polydrug use, a more externalized problems profile. Finally, the implications of these results are discussed.

Background: Suicide rates in the U.S. have continued to rise over the last 2 decades. The increased availability and broader legalization of cannabis is a public health concern, particularly among adolescents. The objective of this study was to examine the association between the age of cannabis initiation and lifetime suicidal ideations and attempts in a sample of adults aged 18 or older. Methods: Data are from the Collaborative Psychiatric Epidemiology Surveys (CPES), 2001 to 2003 (N = 15 238). The primary objective of the CPES was to collect data about the prevalence of mental disorders, impairments associated with these disorders, and their treatment patterns from representative samples of majority and minority adult populations in the U.S. Logistic regression analyses were conducted to test the association between cannabis initiation age (early ⩽14 years old; later >14 years old) and outcomes of lifetime suicide ideation and attempts. Cigarette use, cannabis use, gender, income, race, education, and age were controlled for the analyses. Results: Overall, 12.5% of participants reported suicide ideation, while 4.2% reported attempt. Early cannabis use was associated with a higher risk of suicide ideation (AOR = 3.32, 95% CI [2.75, 3.80]) than later cannabis use (AOR = 2.15, 95% CI [1.92, 2.39]). Early cannabis use was associated with a higher risk of suicide attempt (AOR = 4.38, 95% CI [3.48, 5.52]) than later cannabis use (AOR = 2.56, 95% CI [2.14, 3.06]). Wald chi-squared tests revealed significant differences between the early and late initiation for both ideation (χ2 = 26.99; P < .001) and attempts (χ2 = 26.02; P < .001). Conclusions: Significant associations were found between early initiation of cannabis and suicide behaviors. As suicide rates continue to rise, it is recommended that clinicians, treatment providers, and other professionals consider the use of cannabis at an early age as a risk for subsequent suicide behaviors.

Background: A younger age at onset of use of a specific substance is a well-documented risk-factor for a substance use disorder (SUD) related to that specific substance. However, the cross-substance relationship between a younger age at onset of alcohol use (AU) and nicotine use (NU) and the risk of cannabis use disorders (CUD) in adolescence and early adulthood remains unclear. Aims: To identify the sequence of and latency between initial AU/NU and initial cannabis use (CU). To investigate whether younger age at AU- and NU-onset is associated with any and earlier CU-onset and a higher risk of transition from first CU to CUD, taking into account externalizing disorders (ED) and parental substance use disorders as putative influential factors. Methods: Prospective-longitudinal community study with N = 3021 subjects (baseline age 14–24) and up to four assessment waves over up to ten years with additional direct parental and family history information. Substance use and CUD were assessed with the DSM-IV/M-CIDI. Results: Most subjects with CU reported AU (99%) and NU (94%). Among users of both substances, 93% reported AU prior to CU (87% for NU). After adjustment for ED and parental substance use disorders younger age at AU-onset was associated with any CU. Younger age at NU-onset was associated with earlier CU initiation. Younger age at AU- and NU-onset was not associated with a higher risk of CUD. Conclusions: The cross-substance relevance of younger age at first AU and NU for the risk of CUD is limited to early CU involvement.

Road traffic crashes are a serious public health problem worldwide, and human factors are the most prominent factor of accidents, affecting mostly the young adults. Past studies found that both gender and personality traits such as impulsivity are associated with risky driving, however, the interaction of these predictors is rarely addressed in the literature. To bridge the gap, the present study explores how a specific facet of impulsivity interacts with our hypothesized moderator, gender identification, leads to drug driving using a moderator analysis. We recruited participants from 17 to 35 years old possessing a valid drivers' licence via Facebook advertising. They were invited to complete a questionnaire on their socio-demographic characteristics, cannabis consumption habits and impulsivity scores. A moderator analysis is conducted to disentangle the relationship between sensation seeking, gender and driving after cannabis consumption using SPSS Process. The proposed model contains sensation seeking as an exogenous variable directly associated with driving after cannabis use, and this relationship is moderated by gender identification. The current study provides evidence that sensation seeking and gender identification are not only associated with DACU but also interact to affect driving behaviour. Implications of the study are discussed. / Les accidents routiers constituent de graves problèmes de santé publique dans le monde et les facteurs humains sont connus pour être le principal facteur d'accidents, impliquant principalement les jeunes adultes. Des études antérieures ont démontré que le genre ainsi que des facteurs liés à la personnalité tels que l'impulsivité sont associés à la conduite après consommation récente de cannabis, cependant, l'interaction de ces prédicteurs est rarement abordée dans la littérature. Pour cette raison, cette étude vise à explorer le processus par lequel une facette spécifique de l'impulsivité interagit avec le genre ou le sexe pour modérer la probabilité de prendre le volant après avoir consommé du cannabis. Des participants de 17 à 35 ans possédant un permis de conduire valide ont été recrutés à partir de Facebook par le biais d’annonces payantes. Ils étaient invités à remplir un questionnaire portant sur leur caractéristique socio-démographique, leur habitude de consommation de cannabis, ainsi que sur les composantes de l'impulsivité. Une analyse de modération a été effectuée pour clarifier la relation entre la recherche de sensations, le genre et la conduite d’automobile à l'aide du SPSS PROCESS. Le modèle proposé inclut la recherche de sensations comme variable exogène directement associée à la conduite après la consommation du cannabis, et cette relation est modérée par le genre ressenti. Effectivement, le genre ressenti des participants semble être une variable modératrice de l’association entre la recherche de sensation et la prise de volant après avoir consommé du cannabis. Les implications de ces résultats seront discutées.

The association between extent of chronic cannabis use (CCU-extent) and cognitive impairment among adolescents has been the subject of controversial debate. Linking DNA methylation to CCU-extent could help to understand cannabis associated changes in cognitive performance. We analyzed cognitive task performances, CpG methylation in peripheral whole-blood samples and self-reported past-year CCU-extent of n = 18 adolescents (n = 9 psychiatric outpatients with chronic cannabis use (CCU), n = 9 without) who were matched for age, gender and psychiatric disorders. Patients with CCU were at least 24 h abstinent when cognitive tasks were performed. A Principal Component Analysis (PCA) was carried out to identify group differences in whole genome DNA methylation. Mediation analyses were performed between CCU-extent associated CpG sites and CCU-extent associated variables of cognitive tasks. PCA results indicated large differences in whole genome DNA methylation levels between the groups that did not reach statistical significance. Six CpG sites revealed reduced methylation associated with CCU-extent. Furthermore, CCU-extent was associated with lower scores in verbal learning. All six CpG sites mediated the effects between CCU-extent and verbal learning free recall. Our results indicate that CCU is associated with certain patterns in the methylome. Furthermore, CCU-extent associated impairments in memory function are mediated via differential methylation of the six CCU-associated CpG sits. Six identified CpG are located in genes previously described in the context of neurodegeneration, hippocampus-dependent learning and neurogenesis. However, these results have to be carefully interpreted due to a small sample size. Replication studies are warranted.

The Brisbane Longitudinal Twin Study (BLTS) was being conducted in Australia and was funded by the US National Institute on Drug Abuse (NIDA). Adolescent twins were sampled as a part of this study and surveyed about their substance use as part of the Pathways to Cannabis Use, Abuse and Dependence project. The methods developed in this dissertation were designed for the purpose of analyzing a subset of the Pathways data that includes demographics, cannabis use metrics, personality measures, and imputed genotypes (SNPs) for 493 complete twin pairs (986 subjects.) The primary goal was to determine what combination of SNPs and additional covariates may predict cannabis use, measured on an ordinal scale as: “never tried,” “used moderately,” or “used frequently”. To conduct this analysis, we extended the ordinal Generalized Monotone Incremental Forward Stagewise (GMIFS) method for mixed models. This extension includes allowance for a unpenalized set of covariates to be coerced into the model as well as flexibility for user-specified correlation patterns between twins in a family. The proposed methods are applicable to high-dimensional (genomic or otherwise) data with ordinal response and specific, known covariance structure within clusters.

Background: Polysubstance use (PSU) is common among patients with cannabis use (CU) and is related to more severe CU problems. However, it is unclear how PSU predicts CU treatment outcomes beyond CU patterns. We examined the frequency, amount, and class of additionally used substances as predictors for primary and secondary outcomes. Methods: We conducted crude and adjusted regression analyses for PSU variables as predictors of remission, abstinence, reduction, and secondary outcomes in 166 help-seeking patients from a randomized clinical trial of CANDIS, a cognitive behavioral treatment program. Results: Patients with recent illegal PSU experienced more difficulties in reducing their CU (B = –1.22, p < 0.001). In contrast, remission rates were slightly higher in patients with a wide variety of last-year-PSU (RD = 0.04, p < 0.001). Amphetamine use predicted poorer outcomes regarding CU-related problems (B = –4.22, p = 0.019), and the use of opiates, inhalants, and dissociative substances predicted poorer physical health outcomes (B = –0.62, p = 0.009; B = –0.96, p = 0.039; B = –1.18, p = 0.007). Conclusions: CU treatment is also effective for patients with moderate PSU. However, treatment effects may be enhanced by addressing specific PSU characteristics as part of a modularized program.

Bien que la conduite d’un véhicule motorisé soit une activité des plus usuelles, les accidents routiers font partie des dix premières causes mondiales de décès. Au cours des dernières années, les programmes canadiens et québécois de prévention en sécurité routière ont montré une certaine efficacité, observable notamment par une baisse des décès sur la route. Ces progrès sont toutefois insuffisants, et de meilleures stratégies d’intervention et de prévention doivent être développées. Une meilleure connaissance des personnes susceptibles d’être impliquées dans des accidents routiers permettrait le développement de campagnes plus ciblées et pertinentes. Ainsi, il est déjà reconnu que le fait d’être un homme, le fait d’être âgé entre 15 et 29 ans, et la consommation d’alcool ou de substances psychoactives, augmentaient le risque d’être impliqué dans un accident routier. De ce fait, l’un des objectifs de cette thèse est de mieux comprendre le rôle de la fréquence de consommation de cannabis dans la conduite automobile risquée chez les jeunes conducteurs de sexe masculin. D’autre part, des études se sont déjà intéressées au rôle joué par les parents dans les comportements routiers de leurs jeunes. Aucune étude ne semble toutefois s’être attardée au rôle du soutien à l’autonomie prodigué par les parents dans la prise de risques au volant des jeunes. Le second objectif de cette thèse est donc d’investiguer l’impact du soutien parental de l’autonomie dans la conduite automobile des jeunes consommateurs de cannabis. Dans cette optique, l’Article 1 traite de l’association entre la fréquence de consommation de cannabis et la prise de risques au volant auto-rapportée auprès d’un échantillon de conducteurs masculins âgés entre 18 et 25 ans. De plus, il évalue le rôle du niveau de soutien parental de l’autonomie dans cette prise de risques auto-rapportée. Les résultats indiquent que la fréquence de consommation de cannabis est positivement associée à la prise de risques au volant, telle que mesurée par la variable de conduite sous l’influence du cannabis, et en est un prédicteur. Les résultats de cet article n’ont cependant pu démontrer que le soutien parental de l’autonomie était un prédicteur de la conduite automobile risquée auto-rapportée. L’Article 2 étudie la conduite automobile risquée à travers des données comportementales de conduite automobile risquée, observées dans un contexte de simulation de conduite. Les résultats de ce deuxième article révèlent que la fréquence de consommation de cannabis contribue à prédire la conduite automobile risquée observée. En outre, les résultats indiquent un effet significatif des niveaux de fréquence de consommation sur la prise de risques au volant. Finalement, les résultats révèlent une contribution du niveau de soutien parental à l’autonomie dans la prise de risques au volant observée en simulation. Enfin, la discussion porte sur les contributions théoriques de cette thèse aux connaissances scientifiques en sécurité routière, ainsi que ses implications pratiques pour la prévention et l’intervention. / Although driving a vehicle is one common activity, road accidents are one of the top ten causes of death in the world. In recent years, a decrease of on road deaths in Canada and Quebec have shown that road safety prevention campaigns can be effective. However, these advances are insufficient, and there is a need for better intervention and prevention strategies. A better knowledge of individuals likely to be involved in road accidents would allow the development of more targeted and relevant prevention campaigns. Thus, it is already known that men, individuals aged between 15 and 29, and users of alcohol or psychoactive substances before driving have an increased risk of being involved in a road accident. Therefore, one of the objectives of this thesis is to have a better understanding of the role of frequency of cannabis use in young males’ risky driving. Also, studies have already examined the role of parents in the road behaviors of their children. However, no study seems to have focused on the role of parental autonomy support in young drivers’ risky driving. The second objective of this thesis is to investigate the impact of parental autonomy support on risky driving among young cannabis users. In this line of thinking, Article 1 investigates the association between frequency of cannabis use and self-reported risky driving among a sample of male drivers aged between 18 and 25 years old. In addition, it evaluates the role of parental autonomy support in self-reported risky driving. Results indicate that frequency of cannabis use is positively associated with risky driving (measured with self-reported measure of driving under the influence of cannabis), and is a predictor of this measure. However, results did not show that parental autonomy support is a predictor of self-reported risky driving. Article 2 studies risky driving through behavioral measures. These behavioral measures are observed in a driving simulator. Results of this article reveal a contribution of frequency of cannabis use in predicting observed risky driving in a driving simulator. In addition, results indicate a significant effect of the frequency of use levels on risky driving behaviors observed in the simulated driving task. Finally, results show a contribution of parental autonomy support in observed risky driving in the simulator. The theoretical contributions of this thesis to the scientific literature on road safety, as well as its practical implications for prevention and intervention are discussed.