MedWire News: Patients with bipolar I disorder show disease progression that is random or even "chaotic," suggest findings from a 6-year study that contradict research supporting a predominant, progressive worsening of illness course.
It is widely believed that bipolar I disorder is typically a progressive condition, marked by shortening of wellness intervals and of inter-episode cycles with the passage of years and with rising episode counts.
Indeed, a preliminary review of 40 reports by Ross Baldessarini (Harvard Medical School, Boston, Massachusetts, USA) and colleagues has shown that approximately one-third report findings consistent with this theory.
To investigate further, Baldessarini and team evaluated inter-episode intervals (cycle length) over an average 5.7-year period in 128 clinically treated patients aged on average 30.1 years with DSM-IV-diagnosed bipolar I disorder.
Multivariate analysis showed that factors related to greater cycle length included fewer total episodes or cycles per patient, and longer initial hospitalization. Gender, age at intake, cycle number, and first-episode polarity were not significantly related to cycle length.
When the researchers tested for specific changes in the duration of euthymic intervals among patients with six recurrences from illness onset, they found that a nonsignificant decrease of 2.5% from cycles two to five.
The authors say the findings may have been influenced by treatment effects, but seem to indicate that most current bipolar I disorder patients are unlikely to show progressive shortening of recurrence cycles.
"Nevertheless, it remains of interest to study patients with apparently progressive illnesses… as a potential subgroup of special interest. Such patients should be evaluated for possible biological, clinical, or treatment-response differences from other bipolar I disorder patients," conclude the researchers in the Journal of Affective Disorders.
MedWire (http://www.medwire-news.md/) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2011
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