Background In January, 2014, the Same-Sex Marriage Prohibition Act was signed into law in Nigeria, further criminalising same-sex sexual relationships. We aimed to assess the immediate eff ect of this prohibition act on stigma, discrimination, and engagement in HIV prevention and treatment services in men who have sex with men (MSM) in Nigeria. Methods The TRUST cohort study uses respondent-driven sampling to assess the feasibility and eff ectiveness of engagement of MSM in HIV prevention and treatment services at a clinical site located with a community-based organisation trusted by the MSM community. TRUST is a prospective implementation research cohort of MSM (=16 years) in Abuja, Nigeria. We compared HIV clinical outcomes and stigma, including fear and avoidance of health care, across baseline and quarterly visits before and after implementation of the the Same-Sex Marriage Prohibition Act. Outcomes assessed were measures of stigma and discrimination, loss to follow-up, antiretroviral therapy status, and viral load. We compared outcomes before and after the legislation with χ2 statistics, and estimated incident stigma-related events and loss to follow-up with Poisson regression. Findings Between March 19, 2013, and Aug 7, 2014, 707 MSM participated in baseline study procedures, contributing to 756 before legislation (prelaw) and 420 after legislation (postlaw) visits. Reported history of fear of seeking health care was signifi cantly higher in postlaw visits than in prelaw visits (n=161 [38%] vs n=187 [25%]; p<0 0001), as was avoidance of health care (n=118 [28%] vs n=151 [20%]; p=0 001). In incidence analyses, of 192 MSM with follow-up data and no history of an event at baseline, reported fear of seeking health care was higher in the postlaw than the prelaw period (n=144; incidence rate ratio 2 57, 95% CI 1 29-5 10; p=0 007); loss to follow-up and incident healthcare avoidance were similar across periods. Of the 161 (89%) of 181 HIV-infected MSM with HIV viral loads available, those who had disclosed sexual behaviour with a health-care provider were more often virally suppressed at baseline than those with no previous disclosure (18 [29%] of 62 vs 13 [13%] of 99 men; p=0 013). Interpretation These analyses represent individual-level, quantitative, real-time prospective data for the health-related eff ects resulting from the enactment of legislation further criminalising same-sex practices. The negative eff ects of HIV treatment and care in MSM reinforce the unintended consequences of such legislation on global goals of HIV eradication. Strategies to reach MSM less likely to engage in HIV testing and care in highly stigmatised environments are needed to reduce time to HIV diagnosis and treatment.
