Relationship between neurocognitive functioning and episode recurrences in bipolar disorder

Background: The relationship between neurocognitive impairment and clinical course in bipolar disorder (BD) is inconclusive. The aim of this study was to compare time to recurrence between patients with and without clinically significant cognitive impairment.

Methods: Seventy euthymic patients with BD were included. Based on baseline neurocognitive performance, patients were divided into those with (n=49) and those without (n=21) clinically significant cognitive impairment. Both groups of patients were prospectivelly assessed by a modified life chart method during a mean of 16.3 months.

Results: Patients with some cognitive domain compromised had an increased risk of suffering any recurrence (HR: 3.13; CI 95%: 1.64-5.96), hypo/manic episodes (HR: 2.42; CI 95%: 1.13-5.19), or depressive episodes (HR: 3.84, CI 95%: 1.66-8.84) compared with those patients without clinically significant cognitive impairment. These associations remained significant after adjusting for several potential counfounders such as number of previous episodes, time since last episode, clinical subtype of BD, exposure to antipsychotics, and subclinical symptoms.

Limitations: We classified patients as with or without clinically significant cognitive impairment, although deficits in different cognitive domains may not be equivalent in terms of risk of recurrence.

Conclusions: The results did not support the hypothesis that the experience of successive episodes is related to a progressive neurocognitive decline. On the contrary, cognitive impairment could be the cause more than the consequence of poorer clinical course. Alternatively, a specific subgroup of patients with clinically significant cognitive impairment and a progressive illness in terms of counts of recurrence and shortening of wellness intervals might explain the association showed in this study.