Inattention, hyperactivity, and impulsiveness constitute essential components for the diagnosis of Attention-deficit/hyperactivity disorder (ADHD). Both the diagnosis and medical treatment of ADHD have become highly prevalent during the last two decades. Still, there are considerable regional differences, both within and between countries, in the proportion of children and adolescents with this neuropsychiatric diagnosis. Previous research have shown associations between ADHD with lower socioeconomic status on the one hand and intelligence on the other hand. Hitherto, there is no established objective biological marker for ADHD.
For this interdisciplinary study, we aimed to evaluate these associations' causal directions and strengths using a bi-directional two-sample Mendelian randomization design.[1] We used summary‐level data from the most extensive available genome‐wide association studies (GWAS) to identify genetic instruments for the diagnosis of ADHD, intelligence, and socioeconomic markers, including the Townsend deprivation index, household income, and educational attainment. Effect estimates from individual genetic variants were combined using inverse‐variance weighted regression.
Our results indicate that an ADHD diagnosis may be a direct and robust intelligence-independent consequence of socioeconomic-related factors, whereas ADHD appears only to lead to modestly lowered socioeconomic status. Low intelligence seems not to be a significant independent cause or consequence of ADHD.
The results of this study raise questions about basic assumptions with long historical roots: 1) how children’s conditions and expressions are interpreted in different contexts and 2) how aristocratic norms relate to social practice, pedagogical ideals, and neuropsychiatric diagnoses.
Göteborgs universitet, 2024.