Factors linked to bipolar cycle acceleration identified

Researchers have identified factors that are associated with cycle acceleration in patients with bipolar disorder admitted to hospital for a mood episode.

These factors included being female, having type II rather than type I bipolar disorder and experiencing increasing severity of affective episodes.

These variables have previously been highlighted in patients with rapid cycling, but have received little attention in relation to cycle acceleration, say the researchers, led by Per Finseth (Norwegian University of Science and Technology, Trondheim).

“Thus, the current risk factors may be useful in assessing a progressive course of [bipolar disorder] as well in providing clinical entities for future studies of progressive pathways of recurrence in [bipolar disorder]”, they write in Acta Psychiatrica Scandinavica.

The 210 study participants included 53.3% who were women, 68.1% diagnosed with bipolar I disorder, 31.9% with bipolar II disorder and 47.6% who had experienced cycle acceleration at some point during the course of their illness. Cycle acceleration was defined according to the patients’ own information – whether they had at any point experienced a progressive decrease in the amount of time between mood episodes.

After accounting for confounders, increasing severity of affective episodes was most strongly associated with cycle acceleration, with the next strongest association being bipolar II disorder. Specifically, cycle acceleration was positively associated with having depression as the first mood episode and negatively with the number of hospitalisations for mania.

This suggests that cycle acceleration is associated with depression-dominant bipolar disorder, say the researchers, and may explain why it appears to be less common among patients with bipolar I disorder.

The next most important factor associated with cycle acceleration was having a hypomanic or manic episode triggered by alcohol use or antidepressants. This is “in line with the hypothesis that [antidepressants] and alcohol are involved in stimulating initial affective episodes in a subgroup of patients who later develop a sensitized pattern of spontaneous episodes with a decrease in duration of syndrome-free intervals”, say Finseth et al.

They note that antidepressant use as a trigger was not by itself associated with cycle acceleration, but say that this was a rare factor and deserves further study.

Finally, female gender increased the likelihood of cycle acceleration. Together, the four factors correctly classified 83.7% of patients with and without cycle acceleration, with a sensitivity of 87.2% and a specificity of 80.4%.

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