OBJECTIVE: Some growth hormone deficient adults (GHDAs) have an impaired quality of life, which may improve with growth hormone (GH) treatment. The objective of our study was to make an in-depth psychiatric evaluation of patients with adult-onset (AO) and childhood-onset (CO) GH deficiency (GHD), and to assess the time course of changes in their quality of life and symptoms of depression in response to GH treatment. DESIGN: The study design was a 4-month, double-blind, cross-over, placebo-controlled trial of GH therapy. METHODS:We used a detailed psychiatric interview to characterise 25 patients with proven GHD at baseline. They were reassessed at monthly intervals during treatment with GH or placebo, using the Nottingham Health Profile and two well-recognised depression rating scales. RESULTS: 11/18 (61%) of the patients with AO-GHD, but 0/7 of the patients with CO-GHD, were found to have atypical depression at baseline. There were significant improvements in the depression rating scale scores after 2 months of GH therapy, with significant improvements in emotional reaction and social isolation scores from 1 month, and in energy levels and sleep disturbance from 2 and 3 months respectively. CONCLUSIONS: The results of our study confirm that a large proportion of GHDAs have unequivocal psychiatric morbidity, and suggest that a response to treatment can be seen after a short trial of GH therapy. We hypothesise that this rapid improvement of symptoms of atypical depression represents a direct central effect of GH therapy.