Internet-based cognitive behavioural therapy (iCBT) for perinatal anxiety and depression versus treatment as usual: study protocol for two randomised controlled trials

Women who are pregnant (study 1) or < 12 months postpartum (study 2) with current clinically elevated symptoms of anxiety and/or depression according to validated self-report measures, will be recruited via the research arm of a not-for-profit clinical and research unit in Australia and randomised to the intervention group or treatment as usual control group. The minimum sample size for each study (alpha 0.05; power 0.80 for a g of 0.80) was identified as 50 with at least 10% more to be recruited to account for expected attrition. The co-primary outcome measures are the Patient Health Questionnaire 9-item scale and Generalised Anxiety Disorder 7-item scale to measure depression and anxiety symptom severity, respectively, and will be administered at the following primary time-points: baseline; post treatment; and at one-month follow-up. Psychological distress will be measured according to the Kessler-10 psychological distress scale at each primary time-point and will also be completed before each lesson for those in the intervention group. The total trial period nine weeks for study 1 and 11 weeks for study 2. Program efficacy will be determined using intent-to-treat mixed models. Maintenance of gains will be assessed at one-month follow-up.