The association of childhood attention deficit/hyperactivity disorder (ADHD) with socioeconomic disadvantage

Abstract

Attention deficit/hyperactivity disorder (ADHD) is commonly reported to be more prevalent in children from socioeconomically disadvantaged backgrounds. In this thesis I will explore in more detail the association between socioeconomic disadvantage and ADHD. This thesis comprises six studies, starting with a systematic review in order to evaluate existing published evidence, which is followed by a qualitative study that explores educational practitioners’ conceptualisation of the causes of ADHD. A series of three analyses utilising existing data from the Avon Longitudinal Study of Parents and Children (ALSPAC) then explore which measures of socioeconomic status (SES) are associated with a research diagnosis of ADHD and potential mediators of this association, and whether timing, duration or changes in exposure to financial difficulty impact on the SES-ADHD association. In the final study in this thesis, I explore whether SES-health associations in general are likely to be due to epigenetic differences in children exposed to low SES. Existing literature provides evidence that an association between SES and ADHD is commonly detected. The facet of SES most predictive of ADHD was mother-reported experience of difficulty affording basic necessities (financial difficulty), associated with an increased risk of a research diagnosis of ADHD of 2.23 (95%CI 1.57, 3.16). Exposure to financial difficulty between birth and age seven was associated with higher levels of ADHD symptoms across childhood of 0.78 points on the Strengths and Difficulties Questionnaire Hyperactivity subscale (95% CI 0.54, 1.00, p<0.001), whereas later exposure to financial difficulty was not associated with ADHD symptoms. In addition, I found tentative evidence that different patterns of SES exposure are associated with different levels of ADHD symptoms, with those consistently low SES having symptom scores 0.41 points higher than those in difficulty (95% CI 3.46, 3.57, p<0.001). I did not find strong evidence that low SES impacts on epigenetic profiles across childhood. These findings add to emerging evidence of an association between SES and ADHD that has implications for theory and policy.