Several lines of evidence suggest that the neuropeptide oxytocin (OT) may be involved in the pathophysiology of obsessive-compulsive behavior in humans and repetitive grooming behavior in animals. Trichotillomania (TTM), which is characterized by chronic hair pulling, may be conceptualized as a disorder of pathologic grooming. To investigate the role of OT in TTM, the cerebrospinal fluid (CSF) levels of OT in nine women with TTM and nine healthy female controls were measured. Early findings from this ongoing study fail to demonstrate a significant difference in CSF OT levels between women with TTM and healthy female controls.

While the etiologies of pervasive developmental disorders (PDDs) appear complicated, multifactorial, and relatively poorly understood research over the last 30 to 40 years has implicated certain neurochemicals in the pathophysiology of these diseases. From these studies, a great deal of evidence has emerged supporting a role for serotonergic dysfunction in individuals with autism and related disorders. Recent clinical trials of drugs influencing serotonergic systems have demonstrated promising effects in children, adolescents, and adults with PDDs.

The phenomenological features of 35 obsessive–compulsive disorder (OCD) patients with a lifetime history of tics were compared to 35 age- and sex-matched OCD patients without tics. Seven categories of obsessions and nine categories of compulsions were determined using the symptom checklist of the Yale–Brown Obsessive–Compulsive Scale (YBOCS). Discriminant function analysis revealed that, compared to their counterparts without tics, OCD patients with tics had more touching, tapping, rubbing, blinking and staring rituals, and fewer cleaning rituals, but did not differ on obsessions. These preliminary findings suggest that the types of compulsions present may help to discriminate between two putative subgroups of OCD, i.e. those with and without tics.