In the current study we found a significant interaction between AS and PTSD symptoms on frequency of drinking behavior; however, the direction of the interaction was contrary to our hypothesis. We predicted that AS would moderate the association between severity of PTSD symptoms and drinking behavior such that there would be a more positive association between PTSD symptoms and alcohol consumption among individuals with higher AS; thus the greatest percentage of drinking days was predicted to be among individuals high in AS and with high PTSD symptoms. In contrast to our hypothesis, it was the low AS group whose drinking behavior was more strongly associated with PTSD symptom levels, both for re-experiencing and avoidance symptoms; low levels of PTSD symptoms in this group were associated with relatively fewer days drinking, whereas high levels of PTSD symptoms were associated with more frequent drinking. It should be noted that the reported effects emerged after controlling for week of treatment, which (as would be expected) was strongly associated with drinking behavior.
These results are somewhat surprising in light of existing findings reported in the literature on AS and alcohol use among individuals with anxiety disorders. For example, previous reports with clinical samples found that individuals with high AS report more alcohol use in negative emotion situations than do low AS individuals (e.g., Dehaas et al., 2002
; Dehaas et al., 2001
). It is possible that methodological differences account for the discrepant findings; for example, both of the studies by Dehaas and colleagues operationalized drinking outcomes as responses to a self-report questionnaire (Inventory of Drug Taking Situations; Annis & Martin, 1985
), whereas in the present study degree of drinking was ascertained via patients’ reports about daily drinking behavior based on the Timeline Follow-Back. Nevertheless, the reported results run counter to theoretical expectations, and thus require replication.
Several possible explanations may account for the counterintuitive finding that the highest level of drinking was found among individuals with low AS and high PTSD symptoms. One possibility is that these individuals use alcohol for different reasons than do those with high AS. For example, low AS individuals with high PTSD avoidance symptoms may be “repressors” who deny that high anxiety (PTSD symptoms) is distressing to them (we thank an anonymous reviewer for this interpretation). Thus low AS/high PTSD avoidance individuals may use alcohol in an effort to reduce awareness of their PTSD symptoms. This explanation points to the need for additional research to specify the pathways through which AS moderates the effect of PTSD symptoms on drinking behavior.
Furthermore, it is important to examine drinking motives and other cognitive variables that moderate the association between PTSD symptoms and use of alcohol. Such investigations have been conducted in research on the relationship between social anxiety and alcohol use. For example, Bruch, Rivet, Heimberg, and Levin (1997)
found that social anxiety (shyness) was negatively associated with alcohol use; however, shy individuals who expect alcohol to be helpful in social interactions tend to consume more alcohol. Future research can examine, for example, the effects of alcohol expectancies on the association between PTSD symptoms and alcohol use.
Although the overall pattern of results reported here is the opposite of what we predicted, certain findings were in line with our hypotheses. reveals that, as expected, high AS is associated with greater drinking behavior on average (collapsing across low and high PTSD symptoms; see also ). The most surprising finding is the sharp increase in drinking behavior associated with greater PTSD symptoms among individuals with low AS. Additional research is necessary to determine whether this finding is reliable, if it extends to other outcomes besides drinking behavior, and what accounts for it. Although this finding was not predicted in the present study, at least one previous study reported similar effects associated with low AS; Zvolensky, Kotov, Antipova, Leen-Feldner, and Schmidt (2005)
found that individuals with relatively low AS were more likely to use alcohol under conditions of high stress, whereas for high AS individuals high stress was associated with less
Interestingly, of the three PTSD symptom clusters (re-experiencing, avoidance/numbing, hyperarousal), AS interacted significantly only with avoidance symptoms and marginally significantly with re-experiencing symptoms to predict drinking behavior; this finding is particularly striking in light of the strong correlations among the symptom clusters (see ). While it is possible that these symptom clusters assess the kinds of experiences that tend to provoke greater consumption of alcohol among low AS individuals, additional work is necessary to determine whether the moderating effect of AS is specific to these particular PTSD symptom clusters.
The present results have potential implications for the treatment of individuals with comorbid alcohol use disorders and PTSD. They point to the importance of assessing patients’ levels of AS in order to identify the extent to which their PTSD symptoms and drinking behavior are likely to be associated. Based on the current results, alcohol dependent individuals with low AS are particularly likely to benefit from a reduction in PTSD symptoms in terms of being able to reduce their drinking behavior, whereas individuals with high AS may continue to have problematic levels of drinking even as their PTSD abates. Additional interventions including exposure to interoceptive cues, such as those used to treat panic disorder (e.g., having patients breathe through a straw to induce sensations of suffocation) may complement the standard treatments for PTSD among individuals high in AS, given their overall greater drinking levels.
Strengths of the present study include the large, demographically diverse sample and the use of a clinician-administered PTSD severity measure that makes it unlikely that the results were driven by participants’ response bias. Additionally, the use of a validated measure of drinks consumed (TLFB) rather than more general self-reports about “typical” drinking behavior may more precisely capture participants’ drinking patterns (see Babor, Stephens, & Marlatt, 1997). The present study has several limitations. First, the cross-sectional design precludes conclusion of the causal relationship among AS, PTSD, and drinking. Thus, while it is plausible that individuals with both low AS and high re-experiencing symptoms feel compelled to drink more often, other relationships among these variables are possible. For instance, individuals who drink more and have low levels of AS may be more likely to try to avoid thinking about the trauma memory, thus perpetuating their PTSD symptoms. Longitudinal studies may allow us to determine the direction of these effects, although existing longitudinal research is consistent with the causal role of AS in subsequent self-medication with alcohol (Schmidt et al., 2007
Additionally, although the present sample was diverse in terms of participant race and ethnicity, 70% of participants were male, which likely is a function of the epidemiology of alcohol dependence (e.g., Anthony, Warner, & Kessler, 1994
); however, the majority of patients with PTSD are female (Breslau, 2009
). Thus it may be beneficial to attempt to replicate the current findings in samples that are more gender balanced. However, it is important to note that there were no significant gender effects in the regression models. It also cannot be known from the current results whether these findings extend to other groups that were underrepresented in the present sample, including individuals of Hispanic ethnicity and races other than African Americans and individuals of European descent. Finally, subsequent studies from the present clinical trial (once all outcome data are collected) will address the effects that AS may have on treatment outcome for individuals with comorbid alcohol dependence and PTSD.