This is a randomized, double-blind, placebo-controlled crossover study of single-dose
intranasal oxytocin (24 IU) in 18-55 year-old men with attention deficit/hyperactivity
disorder (ADHD). Following a screening visit to determine eligibility, participants will
return for two main study visits. During the main study visits, study participants will
receive either oxytocin (Syntocinon® nasal spray, Victoria Pharmacy, Zürich, Switzerland) or
placebo (inactive ingredients of Syntocinon® nasal spray, Victoria Pharmacy), followed by
assessments of cognitive control over attention and behavior. Twenty-four participants will
be randomized 1:1 to one of two drug orders, i.e., oxytocin - placebo or placebo - oxytocin.
In an additional neuroimaging substudy, a subset of participants will undergo task-based and
resting-state functional magnetic resonance imaging (fMRI) following oxytocin/placebo
administration to investigate the effects of oxytocin on fMRI activation and functional
connectivity within the cognitive control network.