Sex differences in the interacting roles of impulsivity and positive alcohol expectancy in problem drinking: A structural brain imaging study

Abstract

Alcohol expectancy and impulsivity are implicated in alcohol misuse. However, how these two risk factors interact to determine problem drinking and whether men and women differ in these risk processes remain unclear. In 158 social drinkers (86 women) assessed for Alcohol Use Disorder Identification Test (AUDIT), positive alcohol expectancy, and Barratt impulsivity, we examined sex differences in these risk processes. Further, with structural brain imaging, we examined the neural bases underlying the relationship between these risk factors and problem drinking. The results of general linear modeling showed that alcohol expectancy best predicted problem drinking in women, whereas in men as well as in the combined group alcohol expectancy and impulsivity interacted to best predict problem drinking. Alcohol expectancy was associated with decreased gray matter volume (GMV) of the right posterior insula in women and the interaction of alcohol expectancy and impulsivity was associated with decreased GMV of the left thalamus in women and men combined and in men alone, albeit less significantly. These risk factors mediated the correlation between GMV and problem drinking. Conversely, models where GMV resulted from problem drinking were not supported. These new findings reveal distinct psychological factors that dispose men and women to problem drinking. Although mediation analyses did not determine a causal link, GMV reduction in the insula and thalamus may represent neural phenotype of these risk processes rather than the consequence of alcohol consumption in non-dependent social drinkers. The results add to the alcohol imaging literature which has largely focused on dependent individuals and help elucidate alterations in brain structures that may contribute to the transition from social to habitual drinking.

Keywords: Alcohol expectancy; Cerebral morphometry; Disinhibition; Gender difference; Insula; Social drinking; Thalamus; VBM.

Fig. 1

Comparison of regression slopes between men and women. Significant slope differences are observed in the regression between AUDIT and BIS (t = 2.018, p = 0.045) but not GP, GP × BIS, or age.

Fig. 2

Voxel based morphometry: multiple regressions against global positive alcohol expectancy (GP) and the interaction of GP and Barratt impulsivity (BI) or BI × GP. Posterior insula GMV was reduced in women with increased GP (upper panel), and left thalamus GMV was reduced with increased BI × GP in the combined group (lower panel). (For interpretation of the references to colour in this figure, the reader is referred to the web version of this article.)

Fig. 3

Single-level mediation analysis of (A) global positive alcohol expectancy (GP), right posterior insula (pIns) gray matter volume (GMV) and AUDIT score in women, and (B) the interaction of GP and Barratt impulsivity (BI × GP), left thalamus (thalL) GMV and AUDIT score in men and women combined. Dashed arrows indicate the lack of a significant connectivity at Bonferroni corrected p = 0.05/4 = 0.0125. The asterisk “*” indicates significant mediation.