Drugs age-of-onset as a signal of later post-traumatic stress disorder: Bayesian analysis of a census protocol

(1)Programa de Pós-graduação em Medicina e Saúde (PPgMS), Faculdade de Medicina da Universidade Federal da Bahia, Salvador, Brazil.

(2)Programa de Pós-graduação em Medicina e Saúde (PPgMS), Faculdade de Medicina da Universidade Federal da Bahia, Salvador, Brazil; Universidade Estadual de Feira de Santana, Bahia, Brazil.

(3)Departamento de Psiquiatria da Universidade Federal de São Paulo, São Paulo, Brazil; IoPPN - Institute of Psychiatry, Psychology & Neuroscience (King's College London), UK.

(4)Departamento da Escola de Engenharia de São Carlos, Universidade de São Paulo, São Paulo, Brazil.

(5)Departamento de Neurociências e Saúde Mental, Faculdade de Medicina da Bahia e Serviço de Psiquiatria, Com-HUPES, Universidade Federal da Bahia, Salvador, Brazil.

(6)Department of Epidemiology and Biostatistics, Michigan State University, East Lansing, MI, United States of America.

(7)Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, United States of America.

(8)Programa de Pós-graduação em Medicina e Saúde (PPgMS), Faculdade de Medicina da Universidade Federal da Bahia, Salvador, Brazil; Departamento de Neurociências e Saúde Mental, Faculdade de Medicina da Bahia e Serviço de Psiquiatria, Com-HUPES, Universidade Federal da Bahia, Salvador, Brazil.

(9)Universidade Federal da Bahia, Salvador, Bahia, Brazil. 

Individuals with PTSD have an increased risk of drug use disorders. Conversely, we aim to evaluate how early onset of alcohol, tobacco and psychoactive drugs use are associated with PTSD later in life. 2,193 brazilian young adults completed modularized assessments: The Trauma History Questionnaire, Post-Traumatic Stress Disorder Checklist-Civilian Version (PCL-C, transformed to PCL-5 through a crosswalk procedure), the Barratt Impulsivity Scale; and a survey on drug use with self-report questions about first use, current use, frequency, quantity, and interpersonal consequences. Bayesian inference and multivariate regression models were used to examine the effects on the risk of PTSD, considering different assumptions of information flow. Raw and unbiased (multivariate) estimates consistently revealed that earlier age of onset of alcohol and tobacco use increased risk for PTSD (Odds-ratios between 2.39 and 3.19 (Alcohol) and 1.82 to 2.05 (Tobacco). Among those who had PTSD (310), 10.3% (32) were very precocious at the onset age (12 to 18 years) of alcohol consumption (No-PTSD: 89 out 1883, 4.7%). Data supports a model in which age of onset effects are partially mediated by the number of trauma exposures. Early intoxication might suggest vulnerability for qualifying trauma events, or it may increase chances of exposure. Also, PTSD may be more likely to occur among trauma-exposed individuals with early intoxicating experiences due to alcohol or drug self-administration. The last possibility resonates with the idea that early intoxication might disrupt adolescent brain development, with a subsequent reduction in resilience when qualifying trauma events occur.