Alcohol use disorders and anxiety disorders: relation to the P300 event-related potential

The robust association of alcoholism with reduced P300 event-related potential amplitude has been largely established in severely affected alcoholics and their offspring. Few studies have examined the relationship of increased arousal, anxiety, and P300. In this study, we sought to determine whether P300 group differences could be discerned in well functioning individuals with less severe forms of alcohol use disorders and anxiety disorders. We were particularly interested in looking at the subgroup of alcohol use disorders accompanied by anxiety disorders. This subgroup has previously been found to have diminished alpha amplitude in the resting EEG.

Male and female community volunteers (99 unrelated index participants and 78 relatives) and 21 unrelated volunteers from an anxiety disorder clinic were interviewed by using the Schedule for Affective Disorders and Schizophrenia, Lifetime version. Blind-rated lifetime psychiatric diagnoses were assigned according to DSM-III-R criteria. Auditory and visual P300 event-related potentials were elicited with an oddball paradigm and were recorded at the midparietal (Pz) site.

As expected, auditory P300 amplitudes were significantly reduced in participants with alcohol use disorders and significantly increased in participants with lifetime anxiety disorders. However, more detailed analysis revealed that, in an apparent paradox, auditory P300 amplitudes were lowest in individuals with comorbid alcohol use and anxiety disorders and highest in individuals with anxiety disorders alone. Visual P300 amplitudes followed the same trends but were generally not significant.

Even in a sample of largely community-ascertained individuals, auditory P300 amplitude is reduced in alcoholics, particularly those with anxiety disorders, and is highest in nonalcoholics with anxiety disorders.