Contribution of genetics and early cognitive and emotional development to behaviour problems in middle childhood

There are many possible causes of behaviour problems in school-age children. Looking at which aspects of the child‘s life are associated with behaviour problems at a specific time, such as the family and school environment, are useful for understanding some of the reasons for a child‘s behaviour. However, in order to truly understand some of the causes of behaviour problems we need to have a detailed idea about the genetic and environmental contributions to the child‘s behaviour. Furthermore, by following the same children over time we can find events and characteristics early in the child‘s life that lead to later problems. Once the gene-environment contribution has been established and the early circumstances leading to later problems have been identified, we can use this information to identify, at a young age, children who are likely to experience behaviour problems and to improve their lives. The research proposed here is an attempt to combine the scientific fields of developmental psychology, genetics and brain science in order to obtain this goal.

The proposed study aims at investigating the genetic underpinnings and early precursors of attentional and behavioural problems in middle childhood. These problems characterise disorders such as attention deficit hyperactivity disorder (ADHD), a condition which affects 5.29% of children world-wide (Polanczyk et al., 2007).

The proposed study has two main objectives. Firstly, using data from a national birth cohort of twins (the Twins Early Development Study, TEDS), the genetic contribution to and relationship between emotional and cognitive difficulties in early childhood (age 4) and attentional and behavioural problems in middle childhood (age 9) will be investigated. This question will be investigated using quantitative genetics analyses.

Secondly, a follow-up study of a smaller sample of typical children will be conducted. This group of children was tested several times during infancy on measures of executive functioning (e.g. inhibitory control, working memory), including neural measures, during the applicant‘s PhD work. Executive functioning has been extensively related to the attentional and behavioural difficulties associated with ADHD (Willcutt et al., 2005).

The research question of the follow-up study (Objective 2) is whether measures identified at age 4 in the analyses of the TEDS sample (Objective 1) as (a) having a strong genetic basis and (b) being strongly predictive of behaviour problems in middle childhood, are also related to measures of executive functioning at age 4 and during infancy in the smaller cohort. Parents and children will be invited back for another laboratory visit where children will complete a set of short experimental tasks, and parents will fill in a set of questionnaires, including the ones identified in the TEDS analyses.

This approach of combining analyses of the large twin sample (enabling an estimate of genetic and environmental contributions as well as longitudinal stability) with a targeted follow-up study in the smaller sample based on the initial findings, will enable an investigation of precursors of attentional and behavioural problems in middle childhood starting as early as the first year of life.

We hope to find preliminary evidence of infant and early childhood precursors of behaviour problems in middle childhood. Furthermore, we hope to gain a better understanding of the genetic and environmental contribution to this hypothesised relationship. These results would have important implications for the early identification and treatment of disorders such as ADHD where attentional and behavioural problems constitute a key component. Therefore, the proposed study has both scientific value and practical relevance.