Aim: The overall aim of this thesis was to investigate the association between mental disorder and risk of sexual HIV transmission in a low-income country with a generalized HIV epidemic. Specific objectives were to investigate in Uganda, (1) the association between common mental disorder and sexual risk behaviour, (2) how severe mental disorder could influence sexual risk behaviour, (3) the prevalence of HIV in persons with severe mental disorder, and (4) the association of severe mental disorder with sexual risk behaviour and sexual violence exposure.

Methods:(1) Population-based household survey of 646 Ugandans. Depression, psychological distress and alcohol use were assessed, and questions asked about sexual risk behaviour. (2) Facilitybased qualitative semi-structured interview study of 20 Ugandans, exploring sexual risk behaviour and violence exposure. (3) Facility-based study of HIV prevalence among 602 persons with severe mental disorder. (4) Facility-based study of prevalence of sexual risk behaviour and sexual violence among 602 persons with severe mental disorder, with nationally representative comparison data.

Results: (1) Depression, psychological distress and alcohol use were all associated with sexual risk behaviour, with stronger associations found in women than in men. (2) Severe mental disorder can influence sexual risks by contributing to casual sex during episodes, to rape by non-partners, to exploitation by partners, to non-monogamy in partners, and to sexual inactivity. (3) HIV prevalence was higher in women with severe mental disorder than in women in the general population, but no similar difference was found in men. (4) Severe mental disorder was associated with sexual risk behaviour in women, but not men. In women, severe mental disorder was associated with exposure to sexual violence by a non-partner. The above associations were not confounded by basic socio-demographic variables.