Biological and clinical validation of atypical depression

Depressed patients with (a) mood reactivity alone (MR group), (b) mood reactivity plus one or more associated features (atypical depression, AD group), and (c) patients with neither mood reactivity nor atypical depression (non-MR/AD group) were compared on their cortisol response to 75 mg of desipramine (DMI), a relatively selective norepinephrine reuptake inhibitor. AD patients exhibited a significantly higher cortisol response to DMI compared with MR and non-MR/AD patients, suggesting that atypical depression may be associated with a less impaired norepinephrine system. MR and non-MR/AD patients did not differ, suggesting that mood reactivity alone is not associated with the biological profile observed in atypical depression. Results indicate that while mood reactivity may be necessary for the diagnosis of atypical depression, the additional presence of at least one associated symptom is required for a distinct biological profile. Our findings provide further biological validation of the concept of atypical depression.