Statistical Analysis Plan
Behavioural problems in pre-adolescent children are a large and costly public health problem, which, if not remediated, raise the risk of children showing drug use, criminality, unemployment, poor health and mental health later in life. Many interventions have been developed to prevent these problems but only a few have strong UK evidence of effectiveness, and there is growing Government interest across the UK in finding solutions to these problems. The Incredible Years parent programme has been disseminated across the UK with Government support and shown to be effective in seven randomised trials in different parts of the UK. However it is vital for policy to know for which families and at which ages these interventions are most effective, in order to be sure that they are helping to reduce, rather than widen social inequalities. This is a realistic concern, as we know that for some public health and social interventions (eg Sure Start services), it is the more advantaged families who tend to make better use of these facilities. Surprisingly, there are no clear answers to these questions about social inequality from existing trials of parenting interventions, because each individual trial is quite small. However, we proposed to overcome this problem by combining the data from 11 trials, delivered in a range of community settings, 7 in the UK and 4 in other European countries, making a total of 1460 families in all. The success of the research can be demonstrated in analysis of the data to test whether or not there are differential effects for those with higher or lower levels of social disadvantage, those from different ethnic minority groups, those with younger vs. older children, and those parents experiencing greater behavioural difficulties with their children. We were also able to examine if the costs and cost benefit of the intervention are greater for any of these groups of families. These analyses will help us to target interventions at the parents who will benefit most, and importantly, if there are found to be groups for whom the intervention works less well, it will stimulate change in working practices to try to improve availability and effectiveness of these programmes to such groups.
Using our large pooled data set, we will also be able to answer other vital questions, including the question of what are the wider public health benefits, and cost benefits, of parenting interventions, for improving parenting skill and parent-child relationships, for reducing harsh parenting, for improving parents mental health and well-being. (under well-being, we include depression, parents' confidence in their ability to be a successful parent, and improved partner relationships). We will also test whether the Incredible Years parenting intervention, targeted at one child (often the child the parents are most concerned about) also helps to improve the behaviour of other children in the family. Importantly, we will be able to pool data from all these trials on service-user satisfaction. These data on parents’ views are rarely presented in detail in trial reports, and our study provides a unique opportunity to bring together this information, and examine whether the intervention is perceived as more useful by families with different levels of social disadvantage, from different ethnic groups, or with different child ages and problems, and by the type of service setting attended. We will also be able to examine whether there are any potentially harmful effects from parenting interventions, for example, it could be that introducing new parenting practices into a stressed family can sometimes raise the levels of stress and family conflict. Detecting these possible harms in small trials is not usually possible, but with our large pooled data set we will be much more likely to be able to do this. Finally, by combining our data, we will be able to test which ingredients of the intervention are most important for a successful outcome, for example, is it helping parents to improve their skill at parenting, or is it the sense of confidence and sharing of problems that is gained from attending a group, that is most important? Lessons from these findings will be very helpful in informing parents and practitioners about what aspects of the intervention to concentrate on most.