Bullying Involvement and Adolescent Substance Use: A Study of Multilevel Risk and Protective Factors

Bullying, frequent drunkenness, and frequent cannabis use are significant health-risk behaviours among youth. While many studies have demonstrated that bullying involvement may initiate a developmental pathway to both types of frequent substance use, there is a limited understanding of the connection between these behaviours. The presence of risk and protective factors within youths’ relationships and within their neighbourhoods may alter the associations between bullying involvement and both types of frequent substance use. A systemic approach is needed to assess the complex, social environments in which youth are embedded. The current thesis consists of two studies that examined the associations between bullying and both types of frequent substance use within the context of youths’ social environments. In Study 1, multilevel modeling was used to examine the associations between bullying and frequent substance use within the context of individual and neighbourhood risk factors. Our results indicated that the risk factors associated with both frequent drunkenness and frequent cannabis use exist at both levels, with neighbourhoods altering the association of individual risk factors. Moreover, bullying was a unique risk factor associated with both types of frequent substance use, whereas indirect associations were observed for victimization. Study 2 used a similar methodology to examine the association between bullying and both types of frequent substance use within the context of individual and neighbourhood protective factors. Once again, our results indicated that the protective factors associated with both types of frequent substance use exist at multiple levels, and that neighbourhoods altered the association of individual protective factors. Additionally, positive relationship characteristics interacted with the link between bullying and both types of frequent substance use. Together, these findings clarify the nature of the bullying-substance use link and emphasize the need to study adolescent development in context.

Understanding Adolescents’ Positive and Negative Developmental Experiences in Sport

The purpose of this study was to gain understanding of adolescents’ positive and negative developmental experiences in sport. Twenty-two purposefully sampled adolescent competitive swimmers participated in a semistructured qualitative interview. Content analysis led to the organization of meaning units into themes and categories (Patton, 2002). Athletes suggested their sport involvement facilitated many positive developmental experiences (i.e., related to challenge, meaningful adult and peer relationships, a sense of community, and other life experiences) and some negative developmental experiences (i.e., related to poor coach relationships, negative peer influences, parent pressure, and the challenging psychological environment of competitive sport). Findings underline the important roles of sport programmers, clubs, coaches, and parents in facilitating youths’ positive developmental experiences in sport, while highlighting numerous important directions for future research. Implications for coach training and practice are outlined.

Bridging the link between trauma, brain development and depression: epigenetic mechanisms

Despite its large impact on the individual and society, we currently have only a rudimentary understanding of the biological basis of Major Depressive Disorder, even less so in adolescent populations. This thesis focuses on two research questions. First, how do adolescents with depression differ from adolescents who have never been depressed on (1a) brain morphology and (1b) DNA methylation? We studied differences in the fronto-limbic system (a collection of areas responsible for emotion regulation) and methylation at the serotonin transporter (SLC6A4) and FK506 binding protein gene (FKBP5) genes (two genes strongly linked to stress regulation and depression). Second, how does childhood trauma, which is known to increase risk for depression, affect (2a) brain development and (2b) SLC6A4 and FKBP5 methylation? Further, (2c) how might DNA methylation explain how trauma affects brain development in depression? We studied these questions in 24 adolescent depressed patients and 21 controls. We found that (1a) depressed adolescents had decreased left precuneus volume and greater volume of the left precentral gyrus compared to controls; however, no differences in fronto-limbic morphology were identified. Moreover, (1b) individuals with depression had lower levels of FKBP5 methylation than controls. In line with our second hypothesis (2a) greater levels of trauma were associated with decreased volume of a number of fronto-limbic regions. Further, we found that (2b) greater trauma was associated with decreased SLC6A4, but not FKBP5, methylation. Finally, (2c) greater FKBP5, but not SLC6A4, methylation was associated with decreased volume of a number of fronto-limbic regions. The results of this study suggest an association among trauma, DNA methylation and brain development in youth, but the direction of these relationships appears to be inconsistent. Future studies using a longitudinal design will be necessary to clarify these results and help us understand how the brain and epigenome change over time in depressed youth.