Attention deficit hyperactivity disorder (
ADHD) is a heterogeneous disease whose neurobiological background is not completely understood. It has been proposed that deficits of the inhibitory function with an underactive behavioral inhibition system (BIS) may be in the core of
ADHD. In this regard, this review summarizes all studies that examine the involvement of
cortisol in
ADHD. Differences in
cortisol responses from different
ADHD subtypes, hyperactive/impulsive, inattentive, and combined, are analyzed. In addition, we examine the role of comorbidities as confounding factors in the study of
cortisol in
ADHD, including comorbid
disruptive behavioral disorder (DBD), as well as anxiety and
depressive disorders. Because
ADHD is a neurodevelopmental condition and approximately half of the children enter adulthood with the disorder, we review
cortisol studies in adults and children separately. Two diverse patterns of
cortisol have been reported both in children and adults with
ADHD. Blunted
cortisol responses to stress are associated with comorbid DBD, whereas high
cortisol responses are associated to comorbid
anxiety disorders. Nevertheless, the inhibitory deficits in
ADHD do not appear to be related directly to
cortisol deficits in either children or adults. This review increases our understanding of the heterogeneity of
ADHD and could help in determining new strategies for the treatment of these patients. Future studies including gender and a more systematic methodology to study the
cortisol response are needed.