Data Analytic Plan
We conducted two related analyses, one examining the impact of AUD on the course of PTSD symptoms, and a second examining the impact of any degree of alcohol symptoms on PTSD symptom course. Each analysis consisted of repeated measures multivariant analysis of variance (MANOVA) on three dependent variables: intrusion, avoidance, and hyperarousal symptoms. Independent variables were time and AUD (analysis 1) or alcohol problems (analysis 2). There were no univariate or multivariate within-cell outliers at
p <.001 for either analysis. Results of evaluation of assumptions of normality, homogeneity of variance-covariance matrices, linearity, and multicollinearity were acceptable (
Tabachnick & Fidell, 2001) for both analyses.
Alcohol Use Disorders and PTSD Symptoms
Using Wilks’ criterion, the combined dependent variables were significantly affected by time, F (3, 97) = 25.90, p <.001, and AUD, F (3, 97) = 3.50, p <.05, but not the interaction, F (3, 97) = 1.95, ns. On the basis of univariate tests, time was significant for all three dependent variables: for intrusion, F (1, 99) = 58.40, p <.001; avoidance, F (1, 99) = 31.99, p <.001; and hyperarousal, F (1, 99) = 54.27, p <.001. Scores consistently decreased over time (see for means and standard deviations). AUD was a significant predictor for two of the three dependent variables, intrusion, F (1, 99) = 8.02, p <.01, and avoidance, F (1, 99) = 8.82, p <.01; those who had AUDs had consistently higher scores than those who did not have a history of AUD. Hyperarousal symptoms were not significantly different between the two groups, F (1, 99) = 3.61.
| Table 1Mean Scores and Standard Deviations for Posttraumatic Stress Disorder Clusters as a Function of Time and Alcohol Problems |
Alcohol Problems and PTSD Symptoms
For analysis 2, the combined dependent variables were significantly affected by time, F (3, 97) = 34.94, p <.001; alcohol problems, F (3, 97) = 4.25, p <.01; and the interaction, F (3, 97) = 2.95, p <.05. On the basis of univariate tests, time was a significant predictor for all three dependent variables: for intrusion, F (1, 99) = 72.16, p <.001; avoidance, F (1, 99) = 44.03, p <.001; and hyperarousal, F (1, 99) = 80.76, p <.001. Scores consistently decreased over time (see ). The presence of alcohol problems was significant for all three dependent variables: for intrusion, F (1, 99) = 7.90, p <.01; avoidance, F (1, 99) = 12.45, p <.01; and hyperarousal, F (1, 99) = 4.85, p <.05. Those who had lifetime histories of alcohol problems had consistently higher scores than those who did not. The interaction was not significant for intrusion or avoidance symptoms but was significant for hyperarousal, F (1, 99) = 4.17, p <.05. A plot of the interaction suggested that women who had alcohol problems experienced less symptom improvement over time than women who did not have alcohol problems.