Patients with bipolar disorder are more likely to respond to lithium if the treatment is started early in the course of the condition, say researchers.
Lars Vedel Kessing (University of Copenhagen, Denmark) and team used two definitions of early treatment; the first was treatment initiation after the initial hospital psychiatry contact for a single manic episode versus later contacts and the second was initiation after a single manic or mixed episode versus after a formal bipolar disorder diagnosis.
Regardless of the definition used, patients given earlier treatment were more likely to respond to treatment, the team reports in the British Journal of Psychiatry.
Using the first definition, 15.2% of 4714 patients received lithium at first contact and 84.8% started it later. The probability of an excellent response, defined as having avoided polypharmacy or hospital admission, was 13.3% after 5 years and 8.7% after 10 years for patients who started early, compared with corresponding rates of 6.3% and 4.0% among those who started later.
This equated to a 13% reduction in the risk of not responding, after accounting for confounders including age, gender, and additional diagnoses relating to substance abuse. The findings were similar when the team used the second definition, at a 25% reduced risk of nonresponse.
The researchers stress that they used “rather conservative” definitions of excellent lithium response, having included patients regardless of whether they continued lithium treatment, so may have underestimated the effects of early treatment.
“In clinical practice it is a crucial decision when to start prophylactic treatment with lithium”, they write. “We have no data from randomised trials to guide this decision.”
Vedel Kessing et al say that their observational findings “clearly suggest” that early lithium treatment results in an improved long-term response.
However, they also point out that all the patients in their study were seen by hospital psychiatry units, whether as an inpatient or an outpatient, and that the patients’ median age at inclusion in the study was relatively old for first bipolar disorder onset, at 46.7 years, although the range was very wide. They suggest this may reflect severe or abrupt onset in older bipolar patients, requiring hospital care, or could indicate a long period of undiagnosed bipolar disorder.
“[T]he findings of the study may be generalised only to patients with more severe forms of mania/bipolar disorder who may have a later onset of illness,” say the researchers, “although we find it most likely that early intervention with lithium will also have advantages in younger samples.”
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