We studied error monitoring in ADHD and control children in a task requiring inhibition of a motor response. The extent of slowing following successful (stopped) and failed (nonstopped) inhibition was compared across groups. We also measured the time required to inhibit a response (stop signal reaction time, SSRT). Compared to controls, ADHD participants slowed less following nonstopped responses. Slowing did not vary with comorbid reading, oppositional, conduct or anxiety disorder, sex or ADHD subtype. Slowing after nonstopped responses was marginally, although significantly correlated with total ADHD symptoms and with age. ADHD participants had significantly longer SSRT than controls, but SSRT was not significantly correlated with slowing. The apparent deficit in error monitoring in ADHD and its independence from the inhibition deficit observed in ADHD has implications for executive control models of ADHD, performance problems associated with the disorder and for component theories of executive control.

This preliminary survey indicates that OCD children may have deficits for cognitive flexibility and planning ability and differ from adults with OCD in not presenting with poor response inhibition or memory deficits. Larger, multi-site studies are warranted to help delineate the neurocognitive deficits associated with childhood OCD.

Impaired inhibitory control aggregates in the family members of individuals with ADHD and may serve as an indicator of genetic vulnerability to the disorder.