Background 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. The Thinking Healthy Program (THP), a psychological treatment delivered by community health workers (CHWs) in Pakistan, 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.

Objective To evaluate the effectiveness and cost-effectiveness of THP delivered by peers (the Thinking Healthy Program-Peer delivered in Goa, India; THPP-I) 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 Individual randomized controlled trial in Goa, India involving 280 women. TPs will not be blinded to treatment allocation. Mothers attending antenatal clinics at hospitals will be assessed for eligibility to participate in the trial (e.g. whether they are in the second or third trimester of pregnancy). 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). Women who screen positive (PHQ-9 score ≥ 10) and give informed consent for further participation in the trial will be randomly allocated in a 1:1 ratio to receive enhanced usual care (EUC) or THPP-I+EUC, using a computer generated allocation sequence. The primary outcomes will be remission (i.e. recovery from depression and depressive symptoms), both assessed by the PHQ-9 at 6 months. Secondary outcomes are depressive symptoms and remission at 3 months (PHQ-9), maternal disability at 3 and 6 months (measured with the WHO-DAS), perceived social support, breastfeeding rates and infant weight and height of children at 3 and 6 months. Outcomes will be analyzed on an intention to treat basis.

Interventions EUC will comprise communicating the results of the screening to the mother through an information sheet on self-care for mental health, communicating the results to the mother's gynaecologist, providing the gynaecologist 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-I group will receive, in addition to EUC, between 6 to 14 sessions of THPP starting from their recruitment in the second/ third trimester until up to 6 months after child birth. Sessions will be delivered by peers on an individual basis at a location of convenience to the TPs (usually at their own homes).

Implications THPP-I 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 and mental health services in low resourced settings.

Inclusion Criteria:

• In the 2nd or 3rd trimester of pregnancy
• Aged 18 years and over
• Intending to reside in the selected areas of the intervention delivery for the entire duration of the study (mothers intending to be away for more than 2 months during or after the period of child birth will be excluded).

Exclusion criteria:

• Mothers requiring immediate inpatient care for any reason (medical or psychiatric)
• Mothers who do not speak any of the following languages: Konkani, Hindi, English, Marathi
• Mothers whose expected date of delivery is within 3 weeks of their screening date
• Previously screened using the PHQ-9 within the last month
• Mothers with difficulty hearing/speaking which makes the assessment difficult