Comparing standard and technology-assisted Peer-delivered CBT for Perinatal Depression: A causal mediation study

Background: The ENHANCE non-inferiority trial that took place in a deprived setting in Pakistan, demonstrated that a technology-assisted digital adaptation of the Thinking Healthy Programme (THPTAP), was no different than the face to face Thinking Healthy Programme in improving symptoms of perinatal depression. Examining potential mechanisms through which THP-TAP improved symptoms of perinatal depression, even in the absence of an intervention effect, is key as it can reveal underlying mechanisms of change, providing insight into features the intervention to target to improve outcomes. The present study examines the mechanisms through which THP-TAP improved symptoms of perinatal depressions (or not) compared to the face to face Thinking Healthy Programme. 

Methods: We applied a counterfactual-based approach to mediation, interventional effects, to decompose the total effect of THP-TAP intervention on symptoms of perinatal depression into the following pre-specified indirect effects: number of sessions attended; behavioural activation; perceived social support; problem-solving and cognitive-restructuring skills; and peer empathy.

Results: Perceived social support in THP-TAP arm mediated an improvement in symptoms of perinatal depression compared to the standard face to face Thinking Healthy Programme group (adjusted mean difference in PHQ-9 scores attributable to perceived social support in the technology-assisted digital adaptation of the Thinking Healthy Programme group compared to WHO-THP group: -0.072, bias corrected 95% CI: -0.170, -0.018). There was no difference to support the indirect effects for all other mediators. 

Conclusions: Even in the absence of treatment superiority, our findings suggest that levels of perceived social support was an important feature of the THP-TAP intervention, that resulted in improved symptoms of perinatal depression. From a practical perspective, these findings highlight the importance of social connectedness as a mechanism of change, demonstrating that peer-delivered digital psychosocial interventions can successfully cultivate this relational component