Mismatch negativity on EEG examination is altered among young adults who engage in risky drinking behavior, compared with nondrinkers, and is even more pronounced among people who report risky alcohol use and also have bipolar disorder, a recently published report shows.
Mismatch negativity refers to the automatic electrical activity that occurs in the brain in response to auditory stimulation that incorporates a deviation in a sequence of sounds, and reductions in mismatch negativity are a marker for impairment of NMDA (N-methyl-D-aspartate)-receptor activation. NMDA receptors are thought to be compromised already by alcohol use and in patients with bipolar disorder.
To examine the effects of alcohol use and bipolar disorder on mismatch negativity, EEG with auditory stimuli was performed on 42 bipolar disorder patients and 34 control subjects aged 16-30 years, reported Kate M. Chitty, a PhD candidate at the University of Sydney, Australia, and her associates.
Sixteen of the bipolar disorder patients and 14 of the control subjects engaged in high-risk drinking, while 26 of the patients with bipolar disorder and 20 of the control subjects did not. Alcohol misuse was found to be a strong predictor of attenuations in mismatch negativity, and alcohol’s effect was even more pronounced in bipolar disorder patients than in control subjects. "The attenuated mismatch negativity may reflect an additive effect of alcohol’s antagonistic actions on an already perturbed NMDA/glutamatergic system," the investigators said (Biol. Psychol. 2014;99:60-8).
"Just as glutamatergic agents are becoming increasingly popular in the treatment of bipolar disease, our results suggest that limiting alcohol use could help to control glutamatergic regulation and may be a crucial first step prior to initiating such treatment," they added.
Youths with bipolar disorder have reported lifetime rates of alcohol misuse of up to 70%, and one recent study found that the demographic group most likely to participate in weekly substance use was 20- to 30-year-old males with bipolar disorder, reported Ms. Chitty, who is affiliated with the university’s clinical research unit at the Brain and Mind Research Institute.
Ms. Chitty and her associates cited several limitations of their study. For example, because participants under age 18 years are unable to buy alcohol legally in Australia, it is possible those minors might have been inclined to underreport their alcohol use. Also, the assessment of alcohol use was based on self-report answers to the AUDIT (alcohol use disorder identification test), which is designed to access alcohol use over the last year. "Therefore, information regarding the duration and intensity of the drinking habits beyond this timeframe is limited," they wrote.
Nevertheless, the study suggests that limiting alcohol use might help control glutamatergic regulation and "may be a crucial first step prior to initiating" the treatment of bipolar disorder, Ms. Chitty and her associates wrote.
This study was funded by Australia’s National Health and Medical Research Council; and the New South Wales Health, Mental Health and Drug & Alcohol Office. Ms. Chitty and her associates reported no financial conflicts of interest.