Inclusion and exclusion criteria
| Inclusion criteria | Exclusion criteria |
| Population | |
| At-risk population of parents of infants 0–12 months old in western Organisation for Economic Co-operation and Development countries | Studies including specific groups such as young mothers (mean age <20 years), divorced parents, parents with mental health problems such as schizophrenia and abuse, and children born preterm, at low birth weight or with congenital diseases |
| Intervention | |
| Structured psychosocial parenting intervention consisting of at least three sessions and initiated either antenatal or during the child’s first year of life with at least half of the sessions delivered postnatally | Interventions not focusing specifically on parenting (eg, baby massage, reading sessions with child or breastfeeding interventions), and unstructured interventions (eg, home visits not offered in a structured format) |
| Control group | |
| No restrictions were imposed. All services or comparison interventions received or provided to the control group were allowed. | |
| Outcome | |
| Child development and/or parent–child relationship outcomes | Studies reporting only physical development or health outcomes such as height, weight, duration of breastfeeding and hospitalisation Papers with insufficient quantitative outcome data to generate standardised mean differences (Cohen’s d), ORs and CI |
| Design | |
| Randomised controlled trials (RCT) or quasi-RCTs | Other study designs such as case control, cohort, cross-sectional and systematic reviews |
| Publication type | |
| Studies presented in peer-reviewed journals, dissertations, books or scientific reports | Abstracts or conference papers; studies published in languages other than English, German or the Scandinavian languages (Danish, Swedish and Norwegian) |