The present study aimed to investigate serum
cortisol,
dehydroepiandrosterone (
DHEA), and
oxytocin levels of children with
attention-deficit/hyperactivity disorder (
ADHD) combined presentation and those diagnosed with
ADHD combined presentation and coexisting
conduct disorder. A total of 74 drug-naive children with
ADHD combined presentation alone, 32 children with
ADHD combined presentation +
conduct disorder, and 42 healthy controls were included. The severities of
ADHD and
conduct disorder symptoms were assessed via parent- and teacher-rated questionnaires. The severity of aggression, anxiety, and depression symptoms of the children were assessed by the self-report inventories. Independent of potential confounders, including age, sex, pubertal stage, and severity of depression and anxiety, serum
oxytocin levels of the
ADHD combined presentation +
conduct disorder group were significantly lower than those of both the
ADHD combined presentation alone and control groups. There was also a trend for the
ADHD combined presentation +
conduct disorder group to show lower serum
DHEA levels than that of the
ADHD combined presentation alone group. However, serum
cortisol levels did not show significant alterations among the groups. These findings suggest that
oxytocin and
DHEA may play a role in the pathophysiology of
conduct disorder, at least in the presence of
ADHD combined presentation.