Postpartum depression (PPD) already affects up to 1 in 5 women and left untreated costs $150,000 per case over the lifespan. Under normal conditions, just 10% of women with PPD get evidence-based treatment, a situation that has worsened substantially during COVID-19. The purpose of this study is to a assess if self-referred, online adaptation of a 1-Day Cognitive Behavioural Therapy (CBT)-Based Workshop for PPD delivered up to 30 women at a time can lead to reductions in PPD, if the workshops are cost-effective, and to assess workshop impact on common complications of PPD (anxiety, partner relationship discord, problems with mother-infant attachment). 388 women will be randomized to receive either immediate treatment or treatment 12 weeks later (waitlist control). Study measures will be collected at baseline (immediately before treatment workshop) and 12 weeks later (immediately before wait list control workshop).

The COVID-19 pandemic has further exposed the 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. These women have been among the most affected by the pandemic, experiencing substantial worry, isolation, loneliness, lack of control, and insomnia (1), all of which have increased PPD rates. They also have more responsibilities than ever before, providing care to their infants, toddlers, and older children, while managing their households and supporting their partners. They are also profoundly worried about job losses, reduced income, and food insecurity , all of which have disrupted family routines, increased partner conflict, and rates of intimate partner violence (2).

Postpartum depression (PPD) typically affects up to 1 in 5 women (3-5), increasing the risk of later depressive episodes (6), parenting problems (7), poor mother-infant attachment (8), and emotional, behavioural, and school problems in offspring (9,10). A single case of PPD has been estimated to cost as much as $150,000 over the lifespan (11), 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) (12). Barriers to care include women's preference for psychotherapy over medication, a lack of time, and a reluctance to travel to regular appointments (13,14). The healthcare system is now 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 and decreased access to resources that protect against PPD including social and practical support from family, friends, and professionals. The need for safe and accessible PPD treatment is further highlighted by the uptake of recent recommendations (written by the NPI) on managing PPD during COVID-19 which have been read 40,000 times since their posting (12).

Only interventions that are considered safe and that can be rapidly upscaled can have an impact on PPD at the population level during COVID-19 (15). Ideal large-scale interventions for PPD during COVID-19 are not only safe (i.e., delivered online), but are brief, utilize the treatments most preferred by women (i.e., non-pharmacological), easily accessible (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.

The purpose of this study is to assess if Online 1-Day CBT-Based Workshops for PPD added to care as usual during the COVID-19 pandemic improve PPD more than usual care alone, if the workshops are cost-effective, and if these workshops reduce the impact of the common comorbidities and complications of PPD (anxiety, partner relationship discord, and poorer mother-infant attachment).

388 women who are 18 years or older, have a baby under 1 year old and have an Edinburgh Postnatal Depression Scale (EPDS) score of 10 or more will be randomized to receive either immediate treatment or treatment 12 weeks later (waitlist control) and changes in depression, anxiety, relationship quality, and mother-infant attachment will be compared.

PPD is a major public health issue that has only increased in scope and impact during COVID-19, and no safe, accessible, scalable solutions exist to tackle the scope of this problem. Only health system interventions like ours that utilize existing infrastructure from a previous RCT of face-to-face workshop delivery can be launched expediently on a large scale to significantly improve the health of Canadian women with PPD and their families during this pandemic.

Promising data from a face-to-face trial, and very encouraging recruitment and feasibility findings from the online adaptation of these workshops suggest that self-referred Online 1-Day CBT-Based Workshops can be delivered immediately and rapidly scaled to reduce the impact of COVID-19 on women with PPD and their families. Since the pandemic will have a lasting impact on the delivery of mental healthcare, these online workshops could represent a significant component of the next successfully implemented, research-enabled Canadian public health strategy, and will be applicable globally.

Inclusion Criteria:

• 18 years or older
• infant under 12 months old
• EPDS score 10 or more
• Fluent in written/spoken English

Participants and the research coordinator cannot be blinded to group condition, but staff making reminders and data analysts will not be aware of group status. Therapists delivering groups will be randomly assigned to workshops and not notified of group status.