Attention deficit hyperactivity disorder ADHD is a childhood-onset condition with impairing symptoms of inattention, impulsivity, and hyperactivity. Among the implicated genes, FOXP2 is especially notable because prior work had implicated it in adult ADHD Ribases, and in speech and language disorders [ 95 ].
All these studies suggest that some frequently observed brain and behavioral abnormalities associated with frontal lobe and EF in ADHD may have heritable patterns. There is furthermore emerging evidence for abnormalities in orbital and ventromedial prefrontal and limbic areas that mediate motivation and emotion control.
The results from GWAS showed that common genetic variants, e.
Psychiatric and behavioral comorbidities, such as depression, anxiety disorder, bipolar disorder, substance use, and personality disorders, often co-occur with ADHD and result in increased difficulties for appropriate diagnoses and treatments Barkley and Brown, ; Rosler et al.
Aberrant sensitivity to the size of outcomes has also been reported in ADHD studies 4849and individuals with ADHD have been shown to have little or no change in skin conductance in response to negative outcomes compared with healthy normal individuals 5051 Decades of research have documented and replicated key facts about the disorder for a review, see ref.
Several investigators have suggested that working memory impairment is a core neurocognitive deficit of ADHD Tannock et al. Damage to the brain after birth due to traumatic brain injury has also been considered as a risk factor for ADHD Pineda et al.
While the neurodevelopmental model proposed a double dissociation model that the early onset of cADHD is associated with non-cortical dysfunction, including thalamus and brainstem, that remains static throughout the lifetime; and diminution of symptoms over development was associated with optimal development of PFC.
Family studies that studied the association between ADHD and depression suggest that the co-occurrence is influenced by shared familial factors [ 5455 ].