Patterns of DST positivity in remitted affective disorders

Background: While the Dexamethasone Suppression Test (DST) has been extensi vely used in cross-sectional observations of patients with major affective disorders, studies have tended to ignore the longitudinal application of th e DST in patients stabilized on long-term prophylactic medication. Methods: Monthly DST's were performed on 19 patients, 16 with bipolar disor der and 3 with recurrent major depression. All cases had an excellent respo nse to lithium treatment and family history positive for bipolar disorder. The average duration of observation was 4 years. Results: All patients remained clinically stable throughout the period of o bservation. Eleven patients showed intermittent DST positivity ranging from 10% to 60% of tests, and 2 patients exhibited no positivity. Six patients had fewer than 10% positive DST's, Females showed significantly higher posi tivity than males. The frequency of positivity did not correlate with curre nt age, age of illness onset, duration of illness, duration of lithium trea tment, or season. The risk of primary affective disorders in first-degree r elatives was also unrelated to the frequency of positivity. Conclusions: While the highly selected and small sample population limits g eneralizability, our observations suggest that clinically sufficient lithiu m prophylaxis does not automatically prevent intermittent HPA dysregulation . We hope that a better understanding of this phenomenon will offer new app roaches to the long-term management of mood disorders. (C) 1999 Society of Biological Psychiatry.