Young women are the most vulnerable to postpartum mental illness: A retrospective cohort study in UK primary care.

Background: Whilst childbirth is a leading cause of mental illness in women, how it affects women at different ages is unknown.

Aims: We examine whether the effect of childbirth on mental illness varies at different ages.

Methods: From 2,657,751 women identified from a UK population-based primary care database, 355,864 postpartum periods, with no history of mental illness, were matched on year of birth and general practice to 1,420,350 non-postpartum periods. Cox regression models were used to compare incident mental illness between postpartum and non-postpartum periods. These were measured using hazard ratios (HR) and hazard ratios adjusted for parity and prior pregnancy loss (aHR).

Results: Strong evidence is presented that the effect of livebirth on mental illness was age-dependant for depression (p <0·001), anxiety (p 0·048) and affective psychosis (p 0·031). In 15-19 year olds, depression was over seven times more likely to occur in postpartum periods than non-postpartum periods (aHR 7·09, 95%CI 6·65-7·56); twice the effect in women overall (aHR 3·24 95%CI 3·18-3·29). 15-19 year olds were 50% more likely to develop anxiety in postpartum periods than non-postpartum periods (aHR 1·52, 95%CI 1·38-1·67), with little effect in women overall (aHR 1·07 95%CI 1·04-1·10). Livebirth had over twice the effect on affective psychosis in women aged 15-24 (15-19 year olds: aHR 2·71 95%CI 1·23-5·97; 20-24 year olds: aHR 2·79 95%CI 1·68-4·63) compared to women overall (aHR 1·66, 95%CI 1·29-2·14).

Conclusions: Younger women are far more vulnerable to the effect of childbirth on their mental health, particularly depression and anxiety.