Abstract
This thesis examined whether mental health problems and sexual risk taking were associated in a general population sample and if so, the extent and direction of this association. The thesis begins with a review of theories of risk taking; sexual risk and mental health correlates; and the existing studies linking mental health and sexual risk taking. Three empirical studies were conducted. Study One produced new evidence that a range of psychiatric disorders were linked to early sex (<16 years), risky sex (multiple partners and inconsistent condom use in the past year at age 21) and sexually transmitted infections (STIs) by the age of 21 years. Young people who present with schizophrenia spectrum disorder were also prone to early and risky sex and STIs. Second, depression, the single most common psychiatric problem in the population, was also associated with risky sex and STIs. The risk increased with comorbid psychiatric conditions. Study Two addressed the issue of directionality, specifically examining if childhood behavioural and emotional problems and early adolescent psychiatric disorder predicted later sexual risk taking and STIs. Main findings showed that childhood antisocial behaviour increased the likelihood of risky and early sex, and that low levels of childhood anxiety increased the likelihood of later risky sex and having STIs. Involvement with delinquent peers mediated the association between childhood antisocial behaviour and risky and early sex. To a lesser degree, attachment to parents mediated the association between antisocial behaviour and early sex. These factors did not mediate the association between low levels of childhood anxiety and later sexual outcomes. No associations were found between adolescent psychiatric disorder and later sexual risk taking, with the exception of conduct disorder. However, it is important to note that by excluding the group who had early sex in order to establish temporality, other behaviours of interest exhibited by this group were also excluded. The third study examined whether sexual risk taking was associated with an increased risk of subsequent mental health problems, addressing the issue of directionality in the other direction. Main findings showed that reports of early sex, multiple sex partners and STIs elevated the risk of later substance dependence disorders. Importantly, this association persisted after controlling for baseline levels of psychiatric disorder. Early sex also predicted later conduct disorder, even after controlling for prior conduct disorder. In contrast, early sex, multiple sex partners and acquisition of STIs were unrelated to later diagnoses of anxiety or depression. The significant associations with multiple sex partners and STIs were also shown for incident cases of substance dependence. Moderation analyses revealed no differences between the sexes in any of the studies except in Study Three. Specifically, the association between multiple sex partners and substance dependence appeared to be stronger for males than females for up to 10 sex partners and substantially stronger for females than for males beyond ten sex partners. The final chapter in this thesis reviews the strengths and weaknesses of the studies in this thesis before considering the implications of the results for theory, research and practice.