Objective: To evaluate the neurohormonal and subjective mood response of children with anxiety disorder to clonidine challenge
Method: Children with DSM-IV diagnoses of anxiety disorder (ANX) (n = 24) and normal controls (n = 15) were given a challenge of intravenous clonidine (1.3 micrograms/kg) and provided neurohormonal and mood self-report assessment over a 180-minute period.
Results: The ANX group differed from normal controls in Hamilton Anxiety Rating, Revised Children's Manifest Anxiety Scale score, and maximum change from baseline (delta max) in growth hormone (GH). Clonidine-stimulated GH concentration of the ANX group was significantly elevated compared with that of controls but returned to baseline within 2 hours. A subgroup with obsessive-compulsive disorder (OCD) (n = 9) had significantly higher delta max GH (17.5 +/- 10.1 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 response to clonidine challenge is not blunted in ANX subjects. This finding is in contrast to adult disorder and suggests that adrenergic postsynaptic 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 continuum from childhood to adult anxiety disorder.