CLONIDINE CHALLENGE IN CHILDHOOD ANXIETY DISORDER

Objective: To evaluate the neurohormonal and subjective mood response of children with anxiety disorder to clonidine challenge. Method: Chil dren with DSM-IV diagnoses of anxiety disorder (ANX) (n = 24) and norm al controls (n = 15) were given a challenge of intravenous clonidine ( 1.3 mu g/kg) and provided neurohormonal and mood self-report assessmen t over a 180-minute period. Results: The ANX group differed from norma l controls in Hamilton Anxiety Rating, Revised Children's Manifest Anx iety Scale score, and maximum change from baseline (Delta max) in grow th hormone (GH). Clonidine-stimulated GH concentration of the ANX grou p was significantly elevated compared with that of controls but return ed to baseline within 2 hours. A subgroup with obsessive-compulsive di sorder (OCD) (n = 9) had significantly higher Delta max GH (17.5 +/- 1 0.1 ng/mL) than the group with other anxiety disorders (ANX-OCD) (9.1 +/- 5.8 ng/mL) and controls (5.7 +/- 4.1 ng/mL). Conclusion: GH respon se to clonidine challenge is not blunted in ANX subjects. This finding is in contrast to adult disorder and suggests that adrenergic postsyn aptic receptor down-regulation is not a feature of childhood anxiety. These findings suggest enhanced central adrenergic sensitivity in ANX which is most pronounced in OCD and argue against a neurobiological co ntinuum from childhood to adult anxiety disorder.