Mediators and moderators of ART adherence effects of supporting treatment adherence readiness through training (START): evidence that START helps vulnerable clients achieve better adherence.

Supporting Treatment Adherence Readiness through Training (START) is an HIV antiretroviral adherence intervention, based on the Information Motivation and Behavioral skills (IMB) model, that significantly improved adherence in our randomized controlled trial. To understand how and for whom START had its effects on adherence, we examined mediators and moderators. Ninety-nine HIV-patients (53 control, 46 intervention) who enrolled in the trial and provided month 6 electronic monitored adherence data. The intervention was associated with increased adherence-related knowledge and lower impulsive/careless problem solving, but had no effects on other IMB-related constructs. Neither of these variables mediated the adherence effects of the intervention (based on linear regression models with bootstraping for unbiased standard errors). Four variables interacted with the intervention to moderate its effects: the intervention group had consistent high adherence across the range of depression and time since HIV diagnosis, compared to lower adherence with higher values in the usual care control; those with unstable housing or frequent drug use had higher adherence if in the intervention group compared to the control group. These findings suggest that START provides support that enables its recipients to cope with and overcome challenges (e.g., depression, unstable housing, drug use) that would typically impede adherence.Trial registration: ClinicalTrials.gov identifier: NCT02329782.