Fig 4. The mediating effect of behavioural activation at 3 months on the effectiveness of the HAP on depression severity at 12 months.

Variables as follows: β, Beta coefficient; a, a-path (HAP–mediator); b, b-path (mediator–outcome); c, direct effect (HAP–outcome); a × b, indirect effect. BDI-II, Beck Depression Inventory–II; PHQ-9, Patient Health Questionnaire 9.