A parallel group RCT with experimental (immediate workshop) and waitlist control (treatment 12 weeks later) groups will address our objectives. All participants will be asked to complete study questionnaires at baseline (T1, 3 weeks before the intervention/first workshop) and 12 weeks later (T2, just prior to the waitlist control/second workshop). Workshops will be delivered by trained peer leaders (women who have recovered from PPD). The study will aim to determine if online 1-day CBT-based workshops for PPD delivered by trained lay peers added to care as usual during the COVID-19 pandemic: (1) can improve PPD more than usual care alone, (2) are cost-effective, (3) can reduce the impact of common comorbidities and complications of PPD including anxiety, partner-relationship discord, social support, infant temperament, parenting stress, and poorer mother-infant attachment.

The COVID-19 pandemic has further exposed vulnerabilities in social and economic systems that lead to inequalities for mothers with mental health problems and their children, worsening unintended systematic biases that exist within the healthcare system. Women with postpartum depression (PPD) are experiencing substantial worry (1), isolation, loneliness, and insomnia (2), all of which have increased levels of PPD(3,4). Mothers now have more responsibilities than ever before, providing care to their infants and toddlers, educating their older children, managing households, and supporting their partners. They are also profoundly worried about job losses, reduced income, and food insecurity (5), all of which have disrupted family routines and increased levels of partner conflict and rates of intimate partner violence.(6)

Postpartum depression (PPD) typically affects up to 1 in 5 women (7-9) and increases the risk of later depressive episodes (10), parenting problems (11), poor mother-infant attachment (12), and emotional, behavioural, and school problems in offspring (13,14). A single case of PPD has been estimated to cost as much as $150,000 over the lifespan (15), or $57 billion for each annual cohort of Canadian births.

Even under ideal conditions, the healthcare system is poorly equipped to provide care for problems requiring urgent psychotherapy like PPD (e.g., just 1 in 10 women with PPD receive evidence-based care) (16). Barriers include women's preference for psychotherapy over medication, a lack of time, and a reluctance to travel to regular appointments (17,18). During the pandemic, the healthcare system has become even less able to help these women as public health units that previously supported the mental health of mothers have shifted their priorities to direct COVID response. Moreover, social distancing recommendations aimed at reducing COVID-19 risk have inadvertently increased psychological distress (19) and decreased access to resources that protect against PPD including social and practical support from family, friends, and professionals.

Peer administered interventions (PAIs - those delivered by recovered former patients) are increasingly recognized as potentially effective alternatives to traditional mental health care services (21). Such treatments capitalize on the fact that in the case of psychotherapy, it is not clear that the level of training predicts treatment quality or outcome (22,23) for patients. Depression is an appropriate target for PAIs because it is relatively common, there is substantial unmet treatment need, and recovery rates are high, suggesting that peers will be widely available (21). The few studies that have examined the impact of PAIs for depression suggest they can be effective in both the short and long term but are most effective if: a) they are delivered by peers alone, and b) structured and based on evidence-based treatments (rather than providing non-specific support) (21). In the context of the COVID-19 pandemic peer-delivered interventions are particularly appealing, considering redeployment and re-prioritizing of healthcare providers and services to focus on responding to the pandemic.

Only interventions that are considered safe and that can be rapidly upscaled can have an impact on PPD at the population level (24). Ideal large-scale interventions for PPD during the COVID-19 pandemic are not only safe (i.e., delivered online), but brief, utilize the treatments most preferred by women (i.e., non-pharmacological), reduce barriers to accessibility (i.e., self-referred), provide skills that can be used over the long-term, and delivered in large groups to increase social support. At present time, no interventions exist that meet all of these criteria.

Research Questions Primary Research Question: Can Online 1-Day CBT-Based Workshops for PPD delivered by trained lay peers added to care as usual during the COVID-19 pandemic improve PPD more than usual care alone? Secondary Research Question: Are the workshops cost-effective? Tertiary Research Question: Can these workshops reduce the impact of the common comorbidities and complications of PPD (anxiety, partner relationship discord, social support, infant temperament, parenting stress, and poorer mother-infant attachment)?

Design A parallel group RCT with experimental (immediate workshop) and waitlist control (treatment 12 weeks later) groups will address our objectives. All participants will be asked to complete study questionnaires at baseline (T1, 3 weeks before the intervention/first workshop) and 12 weeks later (T2, just prior to the waitlist control/second workshop). Peers delivering groups will be randomly assigned to workshops and not notified of group status.

Intervention: The experimental (immediate workshop) group will receive the online workshop at baseline (T1), and the control (waitlist) group will receive the intervention twelve weeks later. Both groups can also receive care as usual from their healthcare providers.

The online workshop was developed by the NPI, Ryan Van Lieshout (a perinatal psychiatrist who has developed and tested effective brief group CBT for PPD interventions), Peter Bieling (author of the world's leading group CBT manual), and June Brown (developer of 1-Day CBT-Based workshops for depression in the UK). It is a day-long intervention delivered in 4 modules. Each participant is given a professionally designed manual (Attached) to facilitate learning. Weekly reminder emails are sent for 8 weeks after workshop completion to encourage practice. The investigators also provide a list of PPD resources and a copy of the Canadian Practice Guidelines for the Treatment of PPD (written by NPI).

Lay peers who have recovered from PPD will be recruited (n=5) to be trained to deliver the workshops. The investigators will utilize the CBT training program and screening and safety protocols (e.g., handling suicidality, child safety issues) developed in the context of a previous study where a psychologist and psychotherapist delivered the 1-Day CBT workshops.

Given the situation with COVID-19, the investigators will run the CBT workshops virtually via ZOOM.

Randomization: Women will undergo block randomization to the experimental or waitlist control group using permuted block sizes of 4, 6, and 8. The randomization scheme will be generated in the statistical computing program R. The randomization of participants will be delivered to the research coordinator via the online REDCap (Research Electronic Data Capture) system. The investigators will track reasons for loss to follow-up.

Recruitment: The investigators will recruit participants via social and online media, our public health and community partners, midwifery groups, and obstetrical and family practices.

Inclusion Criteria:

• reside in Ontario
• have an infant <12 months old
• 18 years or older
• EPDS score 10 or more