To test whether receiving care from a health visitor (HV) trained in identification and psychological intervention methods prevents depression 6–18 months postnatally in women who are not depressed 6 weeks postnatally.

The study was a prospective cluster trial, randomized by GP practice, with follow-up for 18 months in 101 primary care teams in the Trent area of England. The participants were women scoring <12 on the postal Edinburgh Postnatal Depression Scale (EPDS) at 6 weeks postnatally (1474 intervention and 767 control women). Intervention HVs (n=89, 63 clusters) were trained in identifying depressive symptoms using the EPDS and face-to-face clinical assessment and in providing psychologically orientated sessions based on cognitive behavioral or person-centered principles. The control group comprised HVs (n=49, 37 clusters) providing care as usual (CAU). The primary outcome measure was the proportion of women scoring ⩾12 on the EPDS at 6 months postnatally. Secondary outcomes were mean EPDS score, Clinical Outcomes in Routine Evaluation – Outcome Measure (CORE-OM) score, State–Trait Anxiety Inventory (STAI), 12-item Short Form Health Survey (SF-12) and Parenting Stress Index Short Form (PSI-SF) scores at 6, 12 and 18 months.

After adjusting for individual-level covariates, living alone, previous postnatal depression (PND), the presence of one or more adverse life events and the 6-week EPDS score, the odds ratio (OR) for EPDS ⩾12 at 6 months was 0.71 [95% confidence interval (CI) 0.53–0.97, p=0.031] for the intervention group (IG) women compared with the control (CAU) group women. Two subgroups were formed by baseline severity: a ‘subthreshold’ subgroup with a 6-week EPDS score of 6–11 (n=999) and a ‘lowest severity’ subgroup with a 6-week EPDS score of 0–5 (n=1242). There was no difference in psychological effectiveness by subgroup (interaction term: z=−0.28, p=0.782).

This study provides new evidence of a universal, enduring preventive effect for depression in women who screen negative for depression postnatally.