Objective: Research concerning the combined effects of alcohol and benzodiazepines on driving-related skills is largely inconsistent. Because as many as 88% of benzodiazepine users report the additional consumption of alcohol, this review aims to provide an updated and concise synthesis of the available high-quality research.
Method: We searched EBSCOhost, PubMed, Scopus, and Web of Science until April 1, 2020, for double-blind, placebo-controlled, repeated-measures intervention trials that examined the effects of alcohol (any dose provided as blood alcohol concentration [BAC]) in combination with oral benzodiazepines on neurocognitive tasks related to driving.
Results: We identified evidence of a substance and timing-dependent interaction for measures of reaction time, tracking, divided attention, and visual functioning. Administering alcohol in conjunction with or shortly after a benzodiazepine resulted in a stronger interactive effect than when administration occurred further apart. An additive and/or synergistic effect often occurred when a therapeutic dose of benzodiazepine was combined with alcohol at a BAC below .05%.
Conclusions: Combined alcohol and benzodiazepine use was associated with significant impairments in driving-related neurocognitive skills. There is a clear need for more high-quality research in this area to better elucidate the mechanisms of alcohol and benzodiazepine interactions. Drivers may be unaware of impairments following the combination of these drugs at legal driving limits. Thus, drivers should be warned to take caution when consuming even small amounts of alcohol while under treatment with benzodiazepines.