Untreated maternal depression during the postpartum period can have a profound impact on the short- and long-term psychological and physical well-being of children. There is, therefore, an imperative for increased understanding of the determinants of depression and depression-related healthcare access during this period.

Respondents were 11 089 mothers of 9-month-old infants recruited to the Growing Up in Ireland study. Of this sample, 10 827 had complete data on all relevant variables. Respondents provided sociodemographic, socioeconomic and household information, and completed the Center for Epidemiologic Studies Depression Scale (CESD).

11.1% of mothers scored above the CESD threshold for depression. 10.0% of depressed mothers and 25.4% of depressed fathers had depressed partners. Among depressed mothers, 73.1% had not attended a healthcare professional for a mental health problem since the birth of the cohort infant. In the adjusted model, the likelihood of depression was highest in mothers who: had lower educational levels (odds ratio (OR) 1.26; 95% confidence intervals (CIs) 1.08, 1.46); were unemployed (OR 1.27; 95% CIs 1.10, 1.47); reported previous mental health problems (OR 6.55; 95% CIs 5.68, 7.56); reported that the cohort child was the result of an unintended pregnancy (OR 1.43; 95% CIs 1.22, 1.68), was preterm (OR 1.35; 95% CIs 1.07, 1.70), or had health/developmental problems (OR 1.20; 95% CIs 1.04, 1.39); had no partner in the household (OR 1.33; 95% CIs 1.04, 1.70) or were living with a depressed partner (OR 2.66; 95% CIs 1.97, 3.60); reported no family living nearby (OR 1.33; 95% CIs 1.16, 1.54); were in the lowest income group (OR 1.60; 95% CIs 1.21, 2.12). The primary determinant of not seeking treatment for depression was being of non-white ethnicity (OR 2.21; 95% CIs 1.18, 4.13).

Results highlight the prevalence of maternal depression in the later postpartum period, particularly for lower socioeconomic groups, those with previous mental health problems, and those with limited social support. The large proportion of unmet need in depressed mothers, particularly among ethnic minority groups, emphasises the need for a greater awareness of postpartum mental health problems and increased efforts by healthcare professionals to ensure that mothers can access the required services.