Are BPI and BPII suicide attempters distinct neuropsychologically?

It is not clear if bipolar disorder I (BPI) and bipolar disorder II (BPII) represent the same disorder on a continuum of severity or two distinct syndromes. Neuropsychological functioning is a means of understanding similarities and differences between diagnostic groups. Objective: To compare the neuropsychological functioning of depressed suicide attempters with BPI or BPII and healthy controls. Methods: Fifty-one individuals with bipolar disorder (BPI n = 32, BPII n = 19) and a history of suicide attempt were compared with 58 healthy controls with respect to neuropsychological functioning in the following domains: motor functioning, psychomotor performance, attention, memory, working memory, impulsiveness and language fluency. Results: Participants with BPI and BPII performed significantly more poorly than healthy controls on tests of Digit Symbol Test of psychomotor functioning, the N Back Test of working memory and the Go-No-Go Test of impulsiveness. Participants with BPI were significantly worse than controls but not those with BPII on the Test of Verbal Fluency. Participants with BPII performed significantly worse than either controls or those with BPI on the Simple Reaction Time Motor Test and the Stroop Test of attention. Conclusion: While participants with both BPI and BPII performed more poorly than healthy controls, individuals with BPII also performed more poorly than those with BPI on some tests suggesting that they may have a unique syndrome. The findings have implications for assessment and treatment in bipolar disorder.