Cognitive functions in euthymic Egyptian patients with bipolar disorder: are they different from healthy controls?

BACKGROUND

There is marked interest to research neurocognitive functions in bipolar disorder during euthymia. Consequently we aimed to study cognitive functions in euthymic bipolar patients and factors affecting them.

METHODS

It is a cross sectional case-control study of 60 euthymic bipolar patients and 30 matched healthy controls. They were subjected to: Structured Clinical Interview for DSM-IV disorders, (SCID-I) to ascertain clinical diagnosis, Young Mania Rating Scale (YMRS), Hamilton Rating Scale for Depression (HRSD) to validate euthymia. Wechsler Adult Intelligence Scale (WAIS) for general intellectual abilities, Wechsler Memory Scale-Revised (WMS-R) for memory, Wisconsin Card Sorting Test (WCST) for executive functions, Continuous Performance Test (CPT) for attention and impulsivity, and an information sheet gathering patient data.

RESULTS

Bipolar patients had statistically significant lower mean IQ scores in all WAIS subscales (p=0.000), significantly lower memory abilities especially digit span and visual memory, higher impulsivity and inattention (p=0.000) but no significant difference in response time by CPT. They displayed significantly lower executive performance on WCST. Patients' years of education correlated positively with IQ. Hospital admission, number, type of episodes and total number of episodes affected memory functions. Hospital admission and number of hypomanic episodes correlated with attention and impulsivity. Previous hospitalization correlated with executive functions.

CONCLUSIONS

Euthymic bipolar patients exhibit cognitive deficits, which correlated with clinical variables as number, type of episodes and previous hospitalization, this knowledge could help minimize cognitive impairments for future patients.

LIMITATIONS: The small sample size, cross sectional design and lack of premorbid cognitive assessment limit generalization of findings.