Co-occurrence of disturbed sleep and appetite loss differentiates between unipolar and bipolar depressive episodes

The aim of this study was to examine whether the co-occurrence of disturbed sleep and appetite loss, two commonly encountered somatic symptoms of depression, can differentiate the clinical expression of depressive episodes between bipolar (BP) and unipolar patients (UP). Forty BP and 40 UP outpatients were interviewed through the Schedules for the Clinical Assessment in Neuropsychiatry (SCAN) and the presence of sleep disturbance and appetite loss during their most severe depressive episode was determined. Other variables studied were patients' gender and age, clinical characteristics related to the course of the disease (age at onset, duration of illness, and number and frequency of depressive and manic episodes), severity of the worst major depressive episode, and presence or absence of certain associated symptoms during that episode (loss of energy, low interest, feelings of guilt and/or self-reproach, impaired concentration, suicidal ideation, and agitation or retardation). Appetite loss was found to be more frequently present in UP (78%) than BP patients (55%, P<.05), No significant difference in the occurrence of sleep disturbance was found between the two groups. Among BP patients, appetite loss was present in 73% of those with sleep disturbance vs. 33% of those without ( P<.02), while no such difference in co-occurrence of sleep disturbance and appetite loss was noticed among UP patients (74% vs. 85%, respectively, n.s.): this finding did not seem to be related to differences in severity of depression among UP and BP patients. Furthermore, those BP patients with co-occurrence of the two somatic symptoms complained also of loss of energy and low interest more often than those without (P<.01 and P<.05, respectively). No similar differences were observed among UP patients. The results of the present study suggest that the pathophysiological mechanisms underlying depressive episodes may differ between BP and UP affective disorder, and that those BP patients with simultaneous occurrence of sleep disturbance and appetite loss can be considered to belong to a particular nosologic subgroup with potential therapeutic and prognostic implications. (C) 2002 Elsevier Science Inc. All rights reserved.