Noradrenergic function in obsessive-compulsive disorder: behavioral and neuroendocrine responses to clonidine and...

To evaluate noradrenergic (NE) function in obsessive-compulsive disorder (OCD), behavioral, physiological, and neuroendocrine responses to the alpha 2-adrenergic agonist clonidine were examined in 18 patients with OCD and 10 healthy subjects. Subjects received single i.v. doses of 2 micrograms/kg of clonidine administered under double-blind, placebo-controlled, random-assignment conditions. Following clonidine, but not following placebo, patients transiently experienced a significant reduction of obsessions and compulsions. Significant drowsiness and a reduction in anxiety were also noted, but the antiobsessional effect appeared independent of the soporific and antianxiety effects. Growth hormone (GH), cortisol, and 3-methoxy-4-hydroxyphenylglycol responses to clonidine did not differentiate patients from healthy controls. Blood pressure and pulse in response to clonidine did not differ between groups. Improvement in OCD symptoms after clonidine significantly correlated with GH response to clonidine, suggesting specific noradrenergic mediation. This finding lends only partial support for a primary defect of noradrenergic function in OCD.