Stigma and prejudice towards sexual diversity negatively affect the mental health of sexual minority individuals. This dissertation contains five empirical studies that tried to fill lacunae in scientific knowledge regarding this association. The first two sought to further insights into antecedents of that link, by studying attitudes towards sexual minority orientations, focusing on the role of education in explaining these attitudes. The effect of educational attainment appeared to be limited, as its association with acceptance of homosexuality was largely confounded by family and individual factors. Within schools, friends affected and were affected by the homophobic attitudes of their peers over time.

The last three empirical chapters studied whether minority stress processes explained mental health disparities between heterosexual and sexual minority individuals, as well as between subgroups of sexual minority individuals. Experiences of parental rejection and bullying victimization partly explained mental health disparities between heterosexual and sexual minority youth, but sociometric analyses did not find sexual minority youth to be more socially isolated in schools than their heterosexual counterparts. Bisexual individuals reported worse mental health than other sexual minority individuals, but dimensions of sexual identity were of limited use in explaining this difference.