BACKGROUND:
The abuse of psychoactive substances markedly increased the burden of disease among young persons all over the world. Men having sex with men (MSM) have increased vulnerability to substance use and its associated disorder for several reasons. This study therefore assessed psychoactive drug use and its associated factors among MSM in southwestern Nigeria

METHODS:
A cross-sectional study was carried out among 305 young MSM (aged 16 -35 years), from three representative states in southwestern Nigeria, selected via respondent-driven sampling. Data were collected using a validated, semi-structured, self-administered questionnaire and analyzed with SPSS version 23. Relevant descriptive and inferential statistics were calculated with level of significance (p) set at <0.05. Strict confidentiality was ensured and participation fully voluntary.

RESULTS:
The mean age of respondents was 25.3 ± 5.7 years; 228 (74.8%) had tertiary education. Psychoactive substance use was reported by 78 (25.6%) respondents; drug dependence was reported by 60 (19.7%) participants. Substance use was associated with transactional sex and unprotected anal sex. Drug dependence was associated with the following: unprotected anal sex; age; gender identity; occupation; educational status; transactional sex; depression; insomnia; suicidal ideation; weakness, violence; bullying; poor concentration and drunkenness.

CONCLUSIONS:
Prevalence of substance use and dependence were high among MSM in southwest, Nigeria. Unprotected anal sex, transactional sex and other psychosocial factors were associated with drug use and dependence. Therefore, concerted efforts at addressing these psychosocial issues are necessary for effective control of psychoactive substance use among MSM in Nigeria.