Cognitive Abilities of Bipolar Patients Not as Uniform as Previously Believed
In the past, research has regularly suggested that bipolar disorder patients show cognitive ability levels midway between that of mentally healthy control patients and patients with schizophrenia. But, researchers and doctors have been uncomfortable with the suggestion that bipolar disorder patients can be so easily categorized, and with good reason. A new study says that patients with bipolar disorder are more accurately separated into three unique groups based on their cognitive performance.
The study, led by Katerine Burdick from the Icahn School of Medicine at Mount Sinai in New York, studied 136 bipolar disorder patients who had completed the MATRICS Consensus Cognitive Battery (MCCB).
One group, making up 28.7 percent of the patients, showed cognitive abilities similar to the 148 mentally healthy control participants, and many showed significantly higher performance for social cognition.
This is “in line with the anecdotal evidence of a high-performing, socially savvy” bipolar disorder subgroup, the team reported in Psychological Medicine.
The second group, comprised of 31.6 percent of the patients, showed selective cognitive impairment. Their performance on the MCCB range from relatively normal to the control participants, to one standard deviation below. The most impairment was shown in processing speed, attention, and social cognition.
According to the study, this group had cognitive abilities similar to what are normally reported for bipolar patients as a whole. However, the third group was found to make up the largest percentage in the study.
The final group, which included 39.7 percent of the patients, had notable cognitive impairment across all domains, with scores between two and three standard deviations below he control scores.
The team noted this group showed deficits very similar to those found in 185 patients with schizophrenia previously tested by the researchers. The bipolar patients did perform better than schizophrenia patients on tests of social cognition, but all other domains were comparable. The researchers concluded:
“By subgrouping [bipolar disorder] patients based on neurocognitive profiles we can reduce the heterogeneity of the phenotype to allow for a more targeted assessment of clinical and biological predictors of cognitive impairment.”