Incredible Years effects are credible in the long-term

Long-term follow-up studies of the effectiveness of parenting interventions are rare. Data are generally only available for conditions prevailing less than six months after a program ends. But the typical pattern is for the effect – at its maximum around the point of completion– to dissipate over time.

In this research, a team from Bangor University, Wales, followed up a successful randomized controlled trial of the Incredible Years BASIC parenting program at 12 and 18 months to see how far the evidence of improved parenting and child behavior was sustained.

They found that the significant gains identified six months after the program started were maintained after 18 months. They covered child behavior, parent behavior, parental stress and depression and were corroborated by observations of sustained improvements in child and parent behaviors.

Two-thirds of the children (63%) had experienced a minimum significant change (0.3 of a standard deviation) at 18 months. Using stricter criteria, 54% made a large change (0.8) and 39% a very large change (1.5). Improvements were more marked for those who completed all three follow-up data collection points (at six, 12 and 18 months) and whose problems were more severe at the outset.

The only exception to the general pattern was a small but significant decrease in self-reported parenting competence, but this was not substantiated by observed parenting skills or reported or observed child behavior.

The Bangor team also found that the frequency and associated cost of health and social service use over time showed a steady but modest decrease over 18 months (there was an increase in the use of special education services). For example, primary care service costs for the previous six months fell from $158 at baseline to $45 at 18 months. The authors suggest that this trend may have been due to fewer child problem behaviors.

The study took place in North- and Mid-Wales Sure Start areas between 2002 and 2006. Families were recruited through health visitors. The index child needed to be three- or four-years-old and to score above the clinical cut-off on the Eyberg Child Behavior Inventory (ECBI) on either the problem or intensity scales.

Families were randomly allocated to either the program group (n=104) or a control group (n=49). Parents in the program group participated in a 12-week parenting program involving weekly two-hour group sessions with a trained leader. High levels of fidelity were achieved through intensive weekly supervision.

The research used standardized outcome measures, including the ECBI and the Parenting Stress Index. Intention-to-treat analysis was conducted, with the ‘last observation carried forward’ for the 25 intervention group families who did not complete all three post-intervention assessments.

The long-term follow-up lacked a control group but it was considered unethical to withhold the program for so long from families in need.

See: Bywater T, Hutchings J, Daley D, Whitaker C, Yeo S T, Jones K, Eames C and Tudor Edwards R. (2009) “Long-term effectiveness of a parenting intervention for children at risk of developing conduct disorder,” British Journal of Psychiatry 195, 1-7. doi: 10.1192/bjp.bp.108.05631.