Explaining how a psychosocial intervention (PROACTIVE) based on behavioural activation improved outcomes of depression in older adults living in deprived regions of Brazil: The mediating roles of reduced loneliness and stepped care

Background: The PROACTIVE trial was a task-shared, stepped and collaborative care, psychosocial intervention based on psychoeducation and behavioural activation in 715 participants (60-94 years; mean (SD) 68·6 (6.9) years; 74·1 % female), that was highly effective at improving recovery from depression among older adults in Brazil. Here we investigate mediators of the intervention's effectiveness.

Methods: Causal mediation analysis using interventional indirect effects, simultaneously decomposed the total effect of PROACTIVE on recovery from depression (PHQ-9 < 10) into multiple indirect effects including: dose of intervention (numbers of sessions and activities completed); social support (Luben Social Network Scale); perceived loneliness (UCLA questionnaire); and additional sessions offered to participants who did not respond during the initial phase of the stepped care intervention.

Results: Of the intervention's total effect (difference in probability of recovery from depression between the intervention and control arms 0·216 [bias-corrected 95 % CI: 0·149, 0·291]): 13 % was mediated through reduced loneliness (0·028 [0·013, 0·046]); and 25 % through attending additional sessions for participants who did not initially respond to the intervention (0·055 [0·007, 0·102]).

Limitations: Due to limitations in our sample size our study may lack power to detect some nuances such as interactions between different mediators.

Conclusions: 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. Importantly, our findings suggest that the intervention's stepped-care component offering additional sessions to participants who did not experience an early response shows promise in ensuring a sustained recovery from depression.