background adhd and autism spectrum disorder (asd) are different neurodevelopmental disorders that often persist into adulthood, but little is known about the differences in neuropsychological functioning between these disorders. Moreover there is no information on the neuropsychological  problems associated with comorbid substance use disorders (sud) in these adults.
aim To explore the different neuropsychological profiles in adults with adhd or asd with or without substance use disorder
method A total of 98 adults with asd (n=63) or adhd (n = 35), with or without a lifetime history of sud, were tested on cognitive functioning in three domains: attention, executive functioning, and intelligence.
results In the absence of lifetime sud, adults with asd performed similar to adults with adhd on attention and most executive functions (ef) tasks, but had a lower processing speed. Adults with asd with a lifetime history of sud were significantly slower on choice reaction time tasks and other processing speed tasks, had a higher variability in reaction time, showed more difficulty with response inhibition, and had lower scores on working memory tasks than adults with asd without a lifetime history of sud. In adults with adhd, a lifetime history of sud was not associated with more problems in attention, executive functioning or intelligence.
conclusions Adults with asd have slower processing speed than adults with adhd, regardless of the sud status. In addition, adults with asd are more impaired by lifetime sud than adults with adhd in the performance on neuropsychological tasks. Therefore, it is important to assess sud history in adults with developmental disorders.