By Lucy Piper, Senior medwireNews Reporter

The course of bipolar illness is rarely chronic but multiple recurrences are common, suggest findings from a 5-year naturalistic study.

Chronicity in terms of uninterrupted persistence of the index episode was seen in only 1.3% of 156 patients with bipolar I or II disorder, the researchers note, but symptoms recurred in 87.0% of 150 patients, with almost half of these experiencing three or more recurrences.

“As a consequence, the patients spent almost one-third of the time in illness episodes and about one-sixth of the time with subthreshold symptoms”, report Erkki Isometsä (University of Helsinki, Finland) and co-workers in Bipolar Disorders. “Half of the time they were euthymic.”

The patients were interviewed at baseline and again at 6 months, 18 months and 5 years using a life-chart method to determine changes in the their mood states.

By five years, 96% of patients had reached full remission of at least 2 months. In multivariate analysis depression and comorbid cluster C personality disorders were found to be “powerful predictors for outcome”.

Indeed, patients with a Hamilton Depression Scale score of 25 or below achieved full remission nearly five times sooner than patients with higher scores, at a median of 6.5 months versus 30.3 months.

Lifetime psychotic symptoms were the only factor to significantly predict recurrence, occurring at a median 4.0 months in patients with compared with 5.7 months in those without such symptoms.

Depression was the predominant illness state. And contrary to the researchers’ expectations, the 82 patients with bipolar II disorder did not spend more time in depressive states than did the 69 bipolar I disorder patients, after accounting for age, gender and index episode.

“Similar proneness to depression may appear counterintuitive to clinicians, who mostly treat patients with [bipolar disorder]-II only for depression, whereas the florid albeit short-lived manic states of patients with [bipolar disorder]-I commonly dominate their perceived clinical picture”, the team comments.

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