What is the best design for early childhood interventions?

After many years of neglect the message is finally out that early childhood is critically important and has long-term effects on individual and maybe even ‘national’ development. Recent findings from neuroscience have shown changes to brain function and structure following disadvantages in early childhood. Furthermore, comprehensive long-term benefits have been reported from high quality early interventions in health, social function, educational attainment, mental health, and even wages. Subsequently, professionals are advocating for early childhood interventions to be conducted at scale. However, there remain many unanswered questions about the content, timing, and duration of such interventions. The South African intervention by Murray et al. began in pregnancy and continued to 6 months of age and was aimed at improving maternal sensitivity and attachment. Attachment did improve but there was no overall benefit on the children’s mental development. The authors suggest that improving maternal sensitivity and attachment may not be sufficient to improve cognition, and opportunities for learning need to be added. It is likely that the content of the intervention determines the type of benefit. For example, interventions focussing on cognitive and language development often benefit those domains but not motor development. In contrast, nutritional interventions often benefit motor development more than mental development. Many functions underpin the development of future functions that appear at an older age; for example, more secure attachment may lead to better social relations and mental health in later childhood and adulthood. Evaluations of immediate impacts therefore do not provide sufficient information and long-term follow-ups are required. Unfortunately, few are available. It is encouraging that benefits to attachment were found a year after the South African intervention stopped. More research is needed on the fit between content of intervention and type of benefit both in the shortand long-term. Another important question posed by the South African intervention is what is the most effective age to begin interventions? Conventional wisdom says the earlier the better but there is little intervention data to support this. Research on sensitive periods suggests that different functions have different timing and duration, and interventions may have different optimal periods depending on the content of intervention and outcomes measured. It is possible that pregnancy and the postnatal period is the most sensitive time for changing maternal responsiveness and subsequent attachment and one explanation may be hormonal changes in pregnancy. Studies of children in residential institutions provide useful information on sensitive periods. Adoption is a comprehensive intervention and Romanian children in residential institutions adopted before 6 months had no measured long-term deficits. This suggests that interventions after age 6 months may be as effective as ones starting earlier. A meta-analysis of interventions in residential institutions showed that children enrolled before 12 months had greater cognitive benefits than those enrolled later and there was a linear relation between age at beginning and effectiveness. Furthermore, in a randomised trial of foster care, the age of fostering was related to improvement in several functions such as IQ and attachment, which improved most in children fostered before 24 months; language improved most in children fostered before 15 months. These findings suggest that interventions should start before 12 months; however, it is unknown how relevant they are to children living at home. Unlike nutritional supplementation with calories and protein that tends to benefit undernourished children under 24 months but little over 24 months, psychosocial interventions beginning later in childhood may be able to remedy deficits where the sensitive periods are wider. Many studies beginning as late as 30 months have had sus-