Clonidine challenge in childhood anxiety disorder

ABSTRACT 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 μg/kg) and provided neurohormonal and mood self-report assessment over a 180-minute period. Result The ANX group differed from normal controls in Hamilton Anxiety Rating, Revised Children's Manifest Anxiety Scale score, and maximum change from baseline (Δmax) 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 Amax 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.