Limitations
depression, deaths, death
The participants in our study were recruited using targeted outreach and peer referral; therefore the sample should not be considered representative of the entire PWID population in these countries. Our participants are likely to be more closely linked to HIV prevention and treatment services, also as a result of study participation [Our algorithm of assessment of the cause of death relied on investigation by the study teams and was restricted by the lack of contact information and considerations of participant confidentiality. This have led to a substantial proportion of deaths due to unknown causes, and in some cases could also introduce a bias. Verification by three physicians should have minimized the chance of misclassification.Most of the measures included in this analysis (ART, OAT receipt, drug use, depression) are self-reported, which is prone to recall and social desirability biases. In a sub-study measuring the presence of ART drugs in blood samples [