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Adverse Childhood Experiences (ACEs) research has proliferated in the last twenty years with significant research demonstrating the detrimental effects of early childhood adversity. While many measures purport to measure ACEs, very few capture the intensity of ACEs while still calculating the traditional “ACEs tally.” Thus, it is the goal of this dissertation to collect evidence for an expanded ACES measure. The Variability in Adverse Childhood Experiences Scale (VACE) measure builds upon the original ACEs and captures interval level data. Two survey-based studies were conducted in which convergent and criterion related validity and test-retest reliability evidence were collected. In Study 1, the traditional ACE tally was not significantly related, through a multiple regression analysis, to depressive symptoms, stress, or substance use F(3, 81) = 1.72, p = .169. VACE scores were only significantly related to depressive symptoms with the entire regression model accounting for only 1% of the total variance in the sample who received the VACE measure F (3,81) = 5.024, p = .003. Childhood Trauma Questionnaire (CTQ-SF) scores were related to depressive symptoms and substance use accounting for 2% of the variance in the sample, F (3, 85) = 8.751, p F (3, 357) = 19.33, VACE score was significantly related to depressive symptoms and substance use with the model accounting for 1.8% of the total variance in the sample F (3,359) = 28.844, p CTQ-SF model accounted for 1.9% of the variance in the sample F (3, 359) = 29.37, p VACE was calculated using a Pearson’s r correlation (r = .854, p r = .664, p VACE (n = 38). The test-retest reliability suggests sufficient temporal stability of the measure across time. The primary goals of modifying an existing ACE measurement to capture greater variability and accumulate validity and reliability evidence for this new measure were achieved.

The pandemic affected daily life on an unprecedented global scale resulting in the need for adaptation and flexibility to cope with ongoing stress, uncertainty, and loss that may affect couple relationships. Understanding resource loss in the context of mass stress events is critical because resource loss has been defined as the primary agent of stress (Hobfoll, 1989). As such, it is important to understand what factors may have shaped the degree of resource loss incurred during the pandemic. Extant research implies that considering early life adversity may be useful to explore as it may be a form of resource loss and is linked to poorer mental health and relational outcomes in adulthood. Furthermore, the stress sensitization hypothesis posits that childhood adversity may prime individuals to have a lower threshold for later life stress. This study utilizes both the stress sensitization hypothesis and the conservation or resources theory as lenses for understanding how childhood adversity affects pandemic-related resource loss for couples. Given that myriad resource loss was a prominent feature of the pandemic, it will be useful to understand whether childhood adversity sets individuals and couples up to experience greater loss in the context of pandemic-related stressors. Additionally, few studies have addressed the influence of mass stressors in the context of couple relationships using data from both partners. This gap in the literature is problematic because the pandemic's unique constraints and stressors were shared and lived in relationships and mental health distress tends to be interrelated among partners. This study is thus designed to examine how family of origin stress (reported at the outset of pandemic related shutdowns in the US in April 2020) associated with posttraumatic stress (PTSS) 3 months later (July 2020) to, in turn, predict variation in resource losses reported 3 months later (October 2020) associated with the COVID-19 pandemic in 535 cisgender, heterosexual couples. Findings showed that individual's higher family of origin stress predicted higher levels of their own PTSS at wave 2, and higher PTSS at wave 2 predicted higher levels of couples' shared resource loss at wave 3. Additionally, family of origin stress associated with higher levels of couples' shared experience of loss via higher levels of their own PTSS.

This work addresses issues in the study of gene-environment interaction (GxE) through research of conduct disorder (CD) among adolescents and extends the recent report of significant GxE and subsequent replication studies. A sub-sample of 1,299 individual participants/649 twin pairs and their parents from the Virginia Twin Study of Adolescent and Behavioral Development was used for whom Monoamine Oxidase A (MAOA) genotype, diagnosis of CD, maternal antisocial personality symptoms, and household neglect were obtained. This dissertation (1) tested for GxE by gender using MAOA and childhood adversity using multiple approaches to CD measurement and model assessment, (2) determined whether other mechanisms would explain differences in GxE by gender and (3) identified and assessed other genes and environments related to the interaction MAOA and childhood adversity. Using a multiple regression approach, a main effect of the low/low MAOA genotype remained after controlling other risk factors in females. However, the effects of GxE were modest and were removed by transforming the environmental measures. In contrast, there was no significant effect of the low activity MAOA allele in males although significant GxE was detected and remained after transformation. The sign of the interaction for males was opposite from females, indicating genetic sensitivity to childhood adversity may differ by gender. Upon further investigation, gender differences in GxE were due to genotype-sex interaction and may involve MAOA. A Markov Chain Monte Carlo approach including a genetic Item Response Theory modeled CD as a trait with continuous liability, since false detection of GxE may result from measurement. In males and females, the inclusion of GxE while controlling for the other covariates was appropriate, but was little improvement in model fit and effect sizes of GxE were small. Other candidate genes functioning in the serotonin and dopamine neurotransmitter systems were tested for interaction with MAOA to affect risk for CD. Main genetic effects of dopamine transporter genotype and MAOA in the presence of comorbidity were detected. No epistatic effects were detected. The use of random forests systematically assessed the environment and produced several interesting environments that will require more thoughtful consideration before incorporation into a model testing GxE.

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Au Canada, 13 % de la population consomme des drogues illicites et il est estimé qu’un jeune sur trois consomme régulièrement du cannabis. Cela génère un fardeau social, coûtant 46 milliards de dollars et entraînant l’hospitalisation de 275 000 personnes. La compréhension des facteurs de risque et des processus menant au développement d’une consommation problématique du cannabis et des autres substances chez les jeunes s’avère ainsi critique. Bien que plusieurs facteurs individuels et environnementaux soient impliqués dans le développement d’une consommation problématique du cannabis et des autres substances, l’adversité à l’enfance et le tempérament impulsif sont identifiés comme deux facteurs de risque importants pour le développement d’une consommation problématique. Cependant, aucune étude n’existe dans la prédiction spécifique des problèmes de consommation du cannabis. L’objectif principal de cette étude a été d’examiner le rôle de l’adversité et de l’impulsivité à l’enfance dans la prédiction d’une consommation problématique du cannabis et des autres substances à l’âge de 24 ans chez des Québécois suivis depuis de leur naissance, et ce dans le cadre d’une étude de cohorte longitudinale. Une relation a été trouvée entre l’adversité à l’enfance et la consommation problématique des substances autres que le cannabis. On retrouve également l’impact de l’impulsivité en tant que facteur de risque pour la consommation problématique des substances autres que le cannabis. Dû à l’absence de résultat significatif quant à la consommation problématique du cannabis, davantage d’études sont nécessaires afin d’explorer son lien avec l’adversité à l’enfance et l’impulsivité. / In Canada, 13% of the population uses illicit drugs and it is estimated that one individual out of three regularly between the ages of 16 to 25 consume cannabis on a regular basis. This creates a social burden, costing $46 billion and leading to the hospitalization of 275,000 individuals. Understanding the risk factors and processes leading to the development of cannabis and other substance use problems in young adult is therefore critical. While it is evident that several individual and environmental factors are involved in the development of cannabis and other substance use problems, childhood adversity and impulsivity have been identified as two important risk factors for the development of problematic cannabis and other substance use. However, there are no studies that examines the specific prediction of cannabis use problems. Thus, the main objective of this study was to examine the role of childhood adversity and impulsivity in the prediction of cannabis use problems in Quebec young adults at age 24, followed since birth in a longitudinal cohort study. A relationship was found between childhood adversity and problematic use of substances other than cannabis at age 24. We also found the impact of impulsivity as a risk factor for problematic consumption of substances other than cannabis. Due to the lack of significant results regarding problematic cannabis use, more studies are needed to explore the link between problematic cannabis use, childhood adversity and impulsivity.

Le décrochage scolaire est un enjeu de taille en raison de ses coûts individuels et sociaux. Des études récentes suggèrent que celui-ci résulte non seulement de l’exposition à des facteurs de risque à long terme, mais aussi de l’exposition proximale à des évènements de vie stressants. Selon le modèle de sensibilisation au stress, le rôle précipitant apparent des stresseurs pourrait être exacerbé chez ceux ayant un historique d’adversité familiale. Cette étude visait à examiner cette hypothèse, en vérifiant d’abord (1) si l’exposition aux évènements stressants et la présence d’adversité familiale perdurant depuis l’enfance étaient directement associées au décrochage scolaire et ensuite (2) si ce type d’adversité exacerbait l’association entre l’exposition à des évènements stressants récents et le décrochage. Ces liens ont été testés auprès d’un échantillon (N = 545) d’adolescents âgés en moyenne de 16 ans (M = 16,5; ÉT = 0,9) surreprésentant les élèves ayant abandonné l’école secondaire avant la diplomation. Au-delà de facteurs confondants potentiels, les résultats suggèrent que les adolescents ayant récemment vécu des évènements de vie stressants sévères sont particulièrement à risque de décrocher, de même que ceux ayant vécu un type d’adversité familiale (ayant mené à un suivi avec la DPJ). Toutefois, les liens directs attendus n’ont pas été observés pour d’autres formes d’adversité familiale (p. ex., problèmes de santé mentale des parents), ni les liens de modération correspondant aux prédictions du modèle de sensibilisation au stress. Ces résultats partiellement concordant avec les hypothèses sont discutés en considérant leurs implications théoriques et pratiques. / High school dropout is a major issue due to its individual and social costs. Recent studies suggest that dropping out results not only from exposure to long-term risk factors, but also from proximal exposure to stressful life events. According to the stress sensitization model, this apparent precipitating role of stressor exposure should be exacerbated among those exposed to family adversity during childhood. The goal of this study was to test this hypothesis, by examining (1) whether exposure to stressful events and the presence of family adversity during childhood were directly associated with high school dropout, and (2) whether this kind of adversity exacerbated the association between exposure to recent stressful events and high school dropout. These associations were tested within a sample (n = 545) of youths aged 16 years old on average (M = 16.5; SD = 0.9) recruited in 12 public high schools located in and around Montreal and overrepresenting early school leavers. After accounting for potential confounders, adolescents who had recently experienced severe stressful life events were found to be more at risk of dropping out, as were those with a history of follow-up with child protection services. However, dropping out was not more frequent among adolescents exposed to other forms of family adversity, namely the presence of family crises and parental chronic mental health problems. Also, the expected sensitization effects were not observed in moderation analyzes. These results partially aligned with hypotheses are discussed in terms of theoretical and practical implications.

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