Testing Phenotypic Models of Posttraumatic Stress Disorder and Alcohol Use Disorder Comorbidity Using Longitudinal Registry Data.

OBJECTIVE

Two predominant phenotypic models of causality exist to explain the high co-occurrence of posttraumatic stress disorder (PTSD) and alcohol use disorder (AUD): the self-medication and susceptibility models. Population-based longitudinal studies that simultaneously examine both models are needed. Thus, the goal of the present study is to test these models using the Swedish National Registries.

METHOD: Registries were used to conduct longitudinal Cox proportional hazard models (n ≈ 1.5 million) and cross-lagged panel models (N ≈ 3.8 million) with follow-up periods of ~23 years.

RESULTS

Covarying for cohort and socioeconomic status, Cox proportional hazards model results found strong support for the self-medication model. Results showed that PTSD predicted increased risk for AUD among both men (HR = 4.58 [4.42, 4.74]) and women (HR = 4.14 [3.99, 4.30]), significantly more so for men (interaction HR = 1.11 [1.05, 1.16]). Support was also found for the susceptibility model, although the effects were lower in magnitude than those for the self-medication model. AUD increased risk for PTSD among men (HR = 2.53 [2.47, 2.60]) and women (HR = 2.06 [2.01, 2.12]), and significantly more so for men (interaction term HR = 1.23 [1.18, 1.28]). Cross-lagged model results of simultaneously testing both models found support for bidirectionality. The PTSD-to-AUD paths and the AUD-to-PTSD paths were of modest effect for men and women.

CONCLUSIONS

The results from both complementary statistical approaches demonstrate that the models of comorbidity are not mutually exclusive. Although the Cox model results evidenced more support for the self-medication pathway, the cross-lagged model results suggest that the prospective relationships between these disorders are nuanced across development.