MedWire News: Suicidality, mood, psychomotor, and neurovegetative symptoms are stable across depressive episodes in bipolar disorder whereas the overall dimensional structure is not temporally stable, US researchers have discovered.
It has been suggested that depressive subtypes in bipolar disorder, characterized by groups of symptoms, have predictive or diagnostic value. However, this assumes that symptoms are stable across mood episodes, a hypothesis that has not been thoroughly investigated.
Roy Perlis, from Massachusetts General Hospital in Boston, and colleagues therefore studied 583 patients with bipolar I and II disorder from the Systematic Treatment Enhancement Program for Bipolar Disorder study who had two depressive episodes during 2 years of follow-up. Syndromal depressive mood episodes were determined using the DSM-IV criteria.
Of the participants, 66.2% had bipolar I disorder, 62.6% were female, 35.9% had a history of psychotic symptoms, 73.4% had a history of rapid cycling, and 41.2% had a history of suicide attempt. In total, 149 patients experienced a third depressive episode, at a median time to recurrence of 168 days.
The greatest stability between first and second depressive episodes was seen for neurovegetative symptoms, psychomotor symptoms, suicidal ideation, and depressed mood, while the least stable symptoms were loss of interest and fatigue.
Significant stability was also observed for the percentage of days irritable and days anxious, as well as for Clinical Global Impression scale scores and the count of DSM-IV mood symptoms. Similar findings were recorded for patients with three depressive episodes.
While a three-factor model including sleep, interest, and guilt had an excellent fit for data from the initial visit, a confirmatory model derived from first-episode data did not fit the second-episode data. Substantial differences in symptom correlations between first and second episodes also reduced the fit of a model in which all factor loadings were constrained to be equal across the two episodes.
The team concludes in the journal Bipolar Disorders: “We identified evidence of consistency of many symptoms between two episodes but with wide variation in the extent of correlation, and substantially less correlation when the episodes are separated by another depressive episode.”
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