Table 1.

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)