What works and for whom in treating depression in older adults in deprived communities in Brazil: Findings from a causal mediation analyses of the PROACTIVE trial that overlapped with the COVID-19 pandemic (preprint)

Background: The PROACTIVE trial was a task-shared, collaborative care, psychosocial intervention that was highly effective at improving recovery from depression in older adults in Brazil that overlapped with the COVID-19 pandemic. Here we investigate mediators of the interventions effectiveness. Methods: Causal mediation analysis using interventional indirect effects, decomposed the total effect of PROACTIVE on recovery from depression (PHQ-9 less than 10), into multiple indirect effects including: dose of intervention (number of sessions and number of activities completed); social support measured through Luben Social Network Scale; perceived loneliness through the three-item UCLA questionnaire; conditions associated with frailty; and extra sessions offered to participants who did not respond to the intervention. Findings: Of the interventions total effect (difference in probability of recovery from depression between the intervention and control arms 0.211 [bias-corrected 95% CI: 0.139, 0.274]): 14% was mediated through improved conditions associated with frailty 0.030 [0.003, 0.065]); 6% through reduced loneliness (0.013 [0.001, 0.028]); and 20% through attending extra sessions for participants who did not respond to the intervention (0.042 [0.007, 0.105]). Interpretation: Our findings emphasise the importance of a home-based intervention to improve depression outcomes where participants are encouraged to self-select activities to mitigate against loneliness and are referred to primary care to manage health issues relating to frailty. Importantly, our findings suggest that offering extra sessions to participants who did not respond to the intervention shows promise in ensuring a sustained recovery from depression.