Treating depression fails to reverse cognitive deficits in bipolar disorder

By Afsaneh Gray, medwireNews Reporter

Successful treatment of depression with total sleep deprivation (TSD) does not improve neuropsychologic deficits in bipolar patients, despite improving clinical symptoms, Italian researchers report.

Although there was no significant improvement in cognitive function after TSD treatment, bipolar patients “did not experience the well known worsening of performance observed in healthy controls after sleep loss,” lead researcher Sara Poletti (Scientific Institute and University Vita-Salute San Raffaele, Milan) and colleagues point out.

A group of 100 biologically unrelated inpatients with a diagnosis of bipolar I disorder, 25% of whom reported previous psychotic symptoms, were matched by age with 100 healthy controls. Patients received antidepressant treatment as needed, except for a subsample of 42 patients who were treated with mood stabilizers alone, and received three consecutive TSD cycles over a 7-day period plus light therapy.

The researchers found that TSD treatment caused a significant decrease in depression, as measured by the Hamilton Depression Rating Scale (HDRS), with 31 patients achieving a full response to treatment, defined as a HDRS score lower than 8 by day 7.

Cognitive function was assessed at baseline and after treatment using the Brief Assessment of Cognition in Schizophrenia (BACS), which evaluates several different cognitive domains: verbal memory, working memory, psychomotor speed and coordination, selective attention, semantic fluency, letter fluency, and executive functions.

As expected, bipolar disorder patients performed less well on baseline cognitive measures than healthy controls. After TSD treatment, there was a significant improvement only in the selective attention domain, “confirming a positive effect of TSD on speed of information processing in bipolar patients,” the authors write in the Journal of Affective Disorders.

There was no difference between patients with and without psychotic features.

There was a significant correlation between medication load and performance on all domains of the BACS; a decrease in medication load was associated with higher cognitive performance. However, this was thought unlikely to account for the deficits seen in bipolar patients.

Poletti and colleagues conclude: “Patients with the greatest cognitive impairment have the poorest social and vocational functioning and patients whose cognition improves demonstrate an improvement in vocational functioning suggesting that cognitive processing deficits may be an important treatment target.”

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