Family, adoption, and twin studies demonstrate a strong genetic contribution to ADHD, which involves polymorphisms in a number of genes, such as those which code for dopamine transporters. Environmental risk factors for ADHD include antenatal exposure to toxins, such as alcohol and tobacco, prematurity, adverse childhood experiences, childhood illness, head trauma, and exposure to environmental toxins.3 The heterogeneity of ADHD may be explained partially by the varying contribution of genes and environmental factors for individual children. ADHD is reported in all ethnic groups and social classes. The prevalence of ADHD in children in the general population ranges from 5% to 11%.3,6
