Randomized controlled trial of a home-visiting intervention on infant cognitive development in peri-urban South Africa.

AIM: To determine whether, in an impoverished South African community, an intervention that benefitted infant attachment also benefitted cognitive development. METHOD: Pregnant females were randomized to intervention (n=220) and no-treatment control groups (n=229). The intervention was home-based parenting support for attachment, delivered until 6 months postpartum. At 18 months, infants were assessed on attachment and cognitive development (Bayley Scales Mental Development Index [MDI]) (n=127 intervention, n=136 control participants). Infant MDI was examined in relation to intervention, socio-economic risk, antenatal depression, and infant sex and attachment. RESULTS: Overall, there was little effect of the intervention on MDI (p=0.094, d=0.20), but there was an interaction between intervention and risk (p=0.03, ηp2=0.02). MDI scores of infants of lower risk intervention group mothers were, on average, 4.84 points higher than those of other infants (p=0.002, d=0.41). Antenatal depression was not significant once intervention and risk were controlled (p=0.08); there was no association between infant MDI and either sex (p=0.41) or attachment (p=0.56). INTERPRETATION: Parenting interventions for infant cognitive development may benefit from inclusion of specific components to support infant cognition beyond those that support attachment, and may be most effective for infants over 6 months. They may need augmentation with other input where adversity is extreme.