Table 6 Characteristics of the included studies investigating associations between breastfeeding and maternal mental health outcomes
Study | Country | Sample size (cases) | Outcome criteria | Time/age at outcome assessment | Exposure | Reference | Crude OR/RR (95% CI) | Adjusted OR (95% CI) | Adjusted variables | NOS scorea |
|---|---|---|---|---|---|---|---|---|---|---|
Cohort studies | ||||||||||
 Hahn-Holbrook 2013 [39] | USA | 160 (24) | EPDS | up to 24 months after delivery | ≥ 3 months | < 3 months | NR | NR | Maternal age, income, education, marital status, parity, preterm birth, maternal employment, ethnicity, and social support | 7 |
 Xu 2014b [46] | Australia | 186,452 (2940) | ICD-10 for schizophrenia | 12 months after delivery | Never | BF | 3.7 (2.5–5.6) | 2.0 (1.3–3.1) | Maternal age, parity, maternal smoking status, socioeconomic status, maternal country of birth, delivery method, gestational age, admission to special care nursery or neonatal intensive care unit, and history of hospital admissions for mental illness | 7 |
Mixed | BF | 2.0 (1.1–4.0) | 1.7 (0.9–3.4) | |||||||
|  |  |  | ICD-10 for unipolar depression |  | Never | BF | 1.0 (0.8–1.2) | 1.0 (0.8–1.2) | ||
|  |  |  |  |  | Mixed | BF | 1.0 (0.8–1.3) | 1.0 (0.8–1.3) | ||
|  |  |  | ICD-10 for bipolar affective disorder |  | Never | BF | 2.5 (1.4–4.3) | 1.9 (1.1–3.5) | ||
|  |  |  |  |  | Mixed | BF | 2.0 (0.9–4.5) | 2.2 (1.0–5) | ||
|  |  |  | ICD-10 for anxiety disorders |  | Never | BF | 0.5 (0.4–0.7) | 0.6 (0.5–0.9) | ||
|  |  |  |  |  | Mixed | BF | 1 (0.7–1.3) | 0.9 (0.7–1.3) | ||
 Park 2018 [35] | South Korea | 1372 (139) | PHQ-9 | >  = 50 years of age | > 47 months | < 23 months | NR | 0.33 (0.16 − 0.68) | Age, smoking, alcohol drinking, job status, education level, household income, marital status, number of pregnancies, obesity, diabetes mellitus, and hypertension | 5 |
|  |  |  |  |  | 24–46 months | < 23 months |  | 0.61 (0.31–1.21) | ||