GENES AND THE ENVIRONMENT IN DEVELOPMENTAL PSYCHOPATHOLOGY LEADING TO SEVERE MENTAL ILLNESS
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Severe mental illness refers to mental disorders that cause functional impairment and interfere with major life activities. Currently, the strongest predictor of severe mental illness is a positive family history. However, most individuals who become ill do not have a family history of severe mental illness. I sought to examine genetic and developmental psychopathology factors that may be used to complement family history information when predicting risk of severe mental illness among youth. First, I examined associations between family history of severe mental illness and two phenotypes that are identifiable early in life: affective lability and basic symptoms. I found that affective lability is associated with a family history of major mood disorders, suggesting that this phenotype is an indicator of familial liability to mood disorders. I also found that basic symptoms are transdiagnostically associated with parental illness severity, suggesting that basic symptoms during childhood are a marker of familial risk of psychopathology. Next, I examined whether genetic scores indexing disposition to intelligence and attention-deficit/hyperactivity disorder (ADHD) predicted exposure to adversity during childhood and adolescence. I found that genetic disposition to ADHD strongly predicted exposure to adversity. However, there was no significant relationship between genetic disposition to intelligence and adversity. This finding suggests that genetic liability to ADHD may be an important early predictor of adverse life experiences. Finally, I described a genetic counselling-based intervention that uses genetic information to communicate risk of developing SMI, depending on whether or not individuals choose to use cannabis. The results of this intervention will provide insight into the acceptability and efficacy of genetic counselling among young people who are not seeking treatment. The findings presented in my thesis will contribute to a better understanding of early risk factors of severe mental illness and will inform future early preventative interventions.