Variable neurocognitive functioning seen in euthymic bipolar patients

By Eleanor McDermid, Senior medwireNews Reporter

A study lends further support to the notion that patients with bipolar disorder have heterogeneous cognitive abilities.

Unlike some previous studies, Diego Martino (Favaloro University, Buenos Aires, Argentina) and co-workers included only patients who were euthymic at the time of testing.

They therefore believe that the heterogeneous neurocognitive functioning they identified could help to explain the variable functional status seen in bipolar disorder patients during periods of euthymia, and, “therefore, could be thought of as a course modifier of the illness.”

The team says this is “a critical issue”, because it may explain why some patients fail to achieve functional recovery despite syndromal remission whereas others maintain a high level of social and occupational functioning even during mood episodes.

The study participants undertook a battery of neurocognitive tests assessing attention, verbal memory, language and executive function. The 100 bipolar patients had poorer cognitive functioning than the 40 mentally healthy controls, with 70.0% versus 27.5% scoring at least 1.5 standard deviations (SDs) below normal values in at least one domain.

Bipolar patients had impaired neurocognition in the attention, verbal memory and executive function domains, with language being preserved. Those with impaired neurocognition also had significantly poorer psychosocial functioning than the controls.

However, 30.0% of the patients had intact neurocognition in all domains, the researchers note in the Journal of Affective Disorders. On the other hand, an additional 30.0% of patients had clinically significant impairments in neurocognition, scoring at least 2 SDs below normal in at least two cognitive domains, compared with 7.5% of controls.

Patients with clinically significant neurocognitive impairments had significantly poorer psychosocial functioning than those with preserved cognition, and tended to have more hospitalisations, at an average of 0.64 versus 0.18, suggesting greater clinical severity.

The researchers note, however, that the difference in neurocognition between these groups was larger than the difference in hospitalisations, “suggesting that other factors beyond clinical variables could be influencing the development of cognitive deficits in [bipolar disorder].”

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