La prévention et la réduction des problèmes liés à la consommation de substances psychoactives par une intervention brève ciblée à la personnalité chez les adolescents présentant des problèmes de santé mentale

Background: In adolescents, mental health disorders frequently co-occurs with substance misuse, a dual diagnosis that tends to complicate the patient’s treatment and prognosis, resulting in astounding costs for society. Thus, it is critical to investigate how to prevent and reduce substance use problems in this population and optimize their global treatment. According to recent literature and to health provincial and federal governments’ priorities, an integrated services approach has been identified as the strategy to favour. In three randomised-controlled trials, brief personality-targeted interventions have shown to be effective in preventing adolescent onset and growth of drinking, binge-drinking and drinking problems. The personality profiles targeted (Hopelessness/Negative thinking, Impulsivity, Anxiety-Sensitivity, Sensation Seeking) play an important role in the onset and development of both substance misuse and psychiatric symptoms. In this thesis, we hypothesized that brief personality-targeted interventions aiming to prevent and reduce substance misuse in a high-risk population would also benefit a psychiatric clinical sample of adolescents.  Methods: To test this hypothesis, 2 studies were conducted as part of this thesis. In the first one, data from an existing sample of adolescents from a school cohort were analysed to determine if among these students, those at high risk of alcohol misuse and presenting with psychiatric symptoms could benefit from this brief intervention. The same intervention was then delivered to a clinical sample of adolescents; this second study was conducted in a psychiatric department in a hospital setting. Results: The first study showed that the intervention was as effective regardless of whether the adolescents reported depression and anxiety symptoms; these symptoms did not moderate the intervention effects on substance misuse and associated problems. However, reporting hyperactivity/impulsivity symptoms and conduct problems did significantly moderate the intervention effects on some drinking outcomes, showing mainly more beneficial intervention effects in adolescents reporting higher levels of externalizing symptoms.  In the second study, no significant intervention effects were found regarding substance use and psychiatric symptoms outcomes. Adolescents who received the intervention significantly had higher rates of follow-up compared to those who did not receive the intervention (p =0,003).  Conclusion: The first study is promising regarding the applicability of the intervention with adolescents with psychiatric disorders’ symptoms. In that sense, the lack of significant findings in the second study could potentially be explained by attrition and small sample size at follow-up and therefore to the statistical limits encountered. It is also possible that the intervention as delivered did not address the issues specific to this clinical population in enough depth.  Nevertheless, it was observed that the evaluation and organization of patient care did not simultaneously include support for patients’ substance use or associated problems. The coordination between treatment and research should be optimized, not only to support the stated mission of governments to harmonize these two dimensions, but also to follow their recommendations as to the need to prioritize the integration of care for patients with comorbid disorders.

Keyphrases: Adolescents, Mental health disorders, Substance use disorders, Concurrent disorders, Personality-targeted intervention