The rates of perinatal depression in South Asian women are reported to be amongst the highest in the world, ranging from 18%-30% in urban areas and 28%-36% in rural areas. In addition to its profound impact on women's health, disability and functioning, perinatal depression is associated with poor child health outcomes such as pre-term birth, infant under-nutrition and stunting. There is robust evidence that perinatal depression can be effectively managed with psychological treatments delivered by non-specialist health care workers. Our previous research conducted in Pakistan led to the development of the Thinking Healthy Program (THP). THP is a psychological treatment delivered by community health workers (CHWs) which more than halved the rate of perinatal depression among mothers and led to significant improvements in child health outcomes. To enhance access to such evidence-based psychological treatments, there is a need to examine the potential role of other human resources such as lay persons in delivering psychological treatments such as THP in poor resource settings.

Objectives To evaluate the effectiveness and cost-effectiveness of THP delivered by peers (the Thinking Healthy Program - Peer delivered in Rawalpindi, Pakistan; THPP-P) over the duration of 6 months. Peers will be healthy mothers who live in the same community as potential trial participants (TPs).

Study design and outcomes Single-blind stratified cluster randomized controlled trial in Rawalpindi, Pakistan (rural area) involving 40 clusters (560 women). TPs will not be blinded to treatment allocation. TPs include all pregnant women in their third trimester of pregnancy who are identified through the list of their local community health worker (Lady Health Worker or LHW). Those who are eligible will be invited to participate in screening for depression; mothers who consent will be screened for depression with a locally validated version of the Patient Health Questionnaire (PHQ-9). TPs who screen positive (PHQ-9 score ≥ 10) receive enhanced usual care (EUC) or THPP+EUC. The primary outcome measures will be remission (i.e. recovery from depression) and reduction in depressive symptoms, both assessed by the PHQ-9 at 6 months post child birth. Secondary outcomes are depressive symptoms and remission at 3 months (PHQ-9), maternal disability at 3 and 6 months post child birth (measured with the WHO-DAS), improved maternal support (measured with MSPSS) at 3 and 6 months post child birth, breastfeeding rates and infant weight and height of children at 3 and 6 months. Outcomes will be analysed on an intention to treat basis.

Interventions EUC will comprise communicating the results to the mother's LHW and medical officer (MO) at the Basic Health Unit (BHU) of her area, providing the MO with the WHO mhGAP guidelines for the treatment of depression, and providing guidance on referral of depressed mothers to mental health services. TPs who are in the THPP group will receive, in addition, 14 sessions of THPP starting from their recruitment in the third trimester until up to 5 months after child birth. Sessions will be delivered by peers on an individual and group basis at a location of convenience to the TPs (usually at their own homes).

Implications THPP has the potential to advance knowledge of the extent to which task-shifting of the delivery of evidence-based psychological treatments can be extended to peers in the community. If effectiveness is observed, this approach offers a potential opportunity to access a vast untapped human resource for maternal mental health care and addresses a major barrier in global mental health - the lack of skilled and motivated human resources in the formal health sector - offering a new avenue for the scaling up of evidence-based psychological treatments in low resourced settings.

Inclusion Criteria:

• Depressive disorder (PHQ-9 (>10 score)),
• In the 3rd trimester of pregnancy,
• Aged 18 years and over,
• Intending to reside in the study area for the entire duration of the study.

Exclusion criteria:

• Mothers requiring immediate inpatient care for any reason (medical or psychiatric),
• Mothers who do not speak any of the following languages: Urdu, Punjabi, Potohari or English.