Effects of Panic Symptoms and Problematic Alcohol Use on Sensitivity to Unpredictable Threat

Individuals with panic disorder (PD) may engage in alcohol use because it effectively dampens their anticipatory anxiety about unpredictable, future panic attacks (i.e., threat). Heightened sensitivity to unpredictable threat (U-threat) may also contribute to risk for problematic drinking and differentiate individuals with PD and comorbid alcohol dependence (AD) from PD-only. To date, the independent effect of problematic alcohol use on reactivity to U-threat is unknown and it is unclear whether prior findings are specific to discrete diagnostic constructs or symptomatology more broadly. Moreover, there is evidence to suggest that resting respiratory sinus arrhythmia (RSA) may be a mediator underlying the association between PD and/or AD and responsiveness to unpredictable threat. The aims of the current study were therefore to examine the unique and interactive effects of panic symptoms and problematic alcohol use (i.e., binge drinking) on startle potentiation and startle responding over time during predictable (P-) and U-threat, and whether resting RSA mediates the associations between panic symptoms/alcohol binges and threat responding. A total of 134 individuals, recruited from the community, completed assessments of panic disorder symptoms and current binge drinking, and resting levels of RSA were collected. Aversive reactivity and responding was measured using a well-validated electromyography (EMG) startle potentiation threat-of-shock paradigm. Results indicated that binge drinking was associated with greater initial startle reactivity and average startle potentiation to U-threat, but not P-threat. Binge drinking also interacted with current panic symptoms such that for those who had no recent binges, elevated panic symptoms were associated with elevated average startle potentiation and less of a decline in startle responding over time during U-threat, and lower levels of resting RSA. In contrast, for those who had recent binge episodes, greater panic symptoms were associated with less initial reactivity to both forms of threat, less average startle potentiation and a typical (or adaptive) decline in startle responding during U-threat. These results suggest that problematic alcohol use does exert important independent effects on sensitivity to U-threat, and also significantly alters the association between panic symptoms and threat responding. The present findings could also suggest that anxious individuals that select to engage in problematic alcohol use are meaningfully different from anxious individuals that do not engage in problematic alcohol use.