Quantitative and qualitative studies of any design were eligible for the review of effectiveness. Participants had to be women who had given birth in the previous 12 months and either met standardised diagnostic criteria for postnatal depression or scored above a cut-off on the Edinburgh Postnatal Depression Scale (EPDS). All interventions with elements described as based on cognitive behavioural principles (including psychoeducation) and conducted in a group setting were eligible. The main outcome for the quantitative review was change in depression measured using EPDS or Beck Depression Inventory.
Included studies varied in the details of the intervention and quality of reporting. Only one intervention was guided by detailed manuals. Other interventions were used alongside group CBT in some studies. Where reported, treatment duration ranged from eight to 12 weeks (one session per week) and group size ranged from four to 20. Comparators were usual care, routine primary care and waiting list group. Studies were carried out in Australia, Chile, UK (one study) and USA.
Final decisions on inclusion or exclusion of studies were made by two reviewers independently. Disagreements were resolved by discussion, with reference to a third reviewer if necessary.