Postnatal Depression Beyond 12 Months: A Systematic Review and Meta-Analysis.

Traditionally, postnatal depression (PND) has been considered as depression in the first year after giving birth, although it has been argued that the 12-month cut-off may be somewhat arbitrary. Specialist perinatal mental health services in England have recently been extended to include women in their second year postpartum; however, there is no good estimate for the prevalence of PND beyond the first year. This review aimed to obtain the best estimate of the prevalence of PND in the second postpartum year. Eligible studies were those that assessed PND and provided a point prevalence using a validated screening tool or clinical diagnosis at least once beyond the first 12 months in women over the age of 18 years in any country. Studies were excluded if they only included women who were already depressed or had elevated depression scores at baseline. PubMed, Embase, Web of Science, CINAHL and PsychINFO were searched in January 2021 (and updated in February 2024) for studies that included the prevalence of PND beyond the first 12 postnatal months. Study quality was assessed using Cochrane's ROBINS-I and Risk of Bias 2 tools. Prevalence data were combined in meta-analysis using prediction intervals (PIs). A total of 6340 papers were found, and of these, 32 studies including 57210 participants across 18 countries met the inclusion criteria and were meta-analysed. The prevalence of PND in the second year (13-24 months) was 15% (95% confidence interval [CI] 12%, 17%; 95% PI 4%, 30%) and similar to that in the first year, 16% (95% CI 14%, 19%; 95% PI 6%, 31%). Despite considerable heterogeneity, common in meta-analysis of prevalence studies, findings show that a similar proportion of women experience PND in the second year after birth.