Traumatic brain injury and alcohol/substance abuse: A Bayesian meta-analysis comparing the outcomes of people with and without a history of abuse

Alcohol and substance (drugs and/or alcohol) abuse are major risk factors for traumatic brain injury (TBI); however, it remains unclear whether outcomes differ for those with and without a history of preinjury abuse. A meta-analysis was performed to examine this issue. The PubMed, Embase, and PsycINFO databases were searched for research that compared the neuroradiological, cognitive, or psychological outcomes of adults with and without a documented history of alcohol and/or substance abuse who sustained nonpenetrating TBIs. Data from 22 studies were analyzed using a random-effects model: Hedges's g effect sizes measured the mean difference in outcomes of individuals with/without a history of preinjury abuse, and Bayes factors assessed the probability that the outcomes differed. Patients with a history of alcohol and/or substance abuse had poorer neuroradiological outcomes, including reduced hippocampal (g=-0.82) and gray matter volumes (g=-0.46 to -0.82), and enlarged cerebral ventricles (g=-0.73 to -0.80). There were limited differences in cognitive outcomes: Executive functioning (g=-0.51) and memory (g=-0.39 to -0.43) were moderately affected, but attention and reasoning were not. The findings for fine motor ability, construction, perception, general cognition, and language were inconclusive. Postinjury substance and alcohol use (g=-0.97 to -1.07) and emotional functioning (g=-0.29 to -0.44) were worse in those with a history of alcohol and/or substance abuse (psychological outcomes). This study highlighted the type and extent of post-TBI differences between persons with and without a history of alcohol or substance abuse, many of which may hamper recovery. However, variation in the criteria for premorbid abuse, limited information regarding the history of abuse, and an absence of preinjury baseline data prevented an assessment of whether the differences predated the TBI, occurred as a result of ongoing alcohol/substance abuse, or reflected the cumulative impact of alcohol/substance abuse and TBI.