Attention-deficit hyperactivity disorder (ADHD) is the most common developmental disorder of childhood. ADHD can affect a person's ability to function at school, at home, and in social settings and is one of the more common reasons for referral to pediatric neurologists, neuro developmental pediatricians, and child psychiatrists. Etiological investigations of ADHD suggest a strong genetic contribution, accounting for as much as 85% of the risk. Multifactorial patterns of inheritance are seen with a complex genetic network, frequently linked to catecholaminergic (particularly dopaminergic) neurotransmitter systems. Both animal and human studies report on the sensitivity of the dopamine system to hypoxia and ischemia. Similarly, injuries to the frontal-subcortical circuits, including cortical lesions associated with stroke and trauma and shearing white matter injuries associated with trauma are shown to result in ADHD symptoms. Evidence of such mechanisms for the development of ADHD is also borne out in the perinatal outcome literature. Although ADHD was originally conceived of as a developmental disorder occurring in childhood, it is now apparent that symptoms often persist into adulthood. Genetic factors can result in affected adults having children with ADHD and associated parent child problems. Current literature suggests continuing benefit from treatment of ADHD in affected adults, leading to reductions in symptoms and improved functioning.
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