Cocaine-Cannabis Combination Was a Risk Factor for Repeat Impaired Driving

Polydrug use was a significant risk factor for driving recidivism compared to monodrug use (OR=1.99). Among polydrug combinations, only cocaine combined with cannabis was a significant risk factor (OR=1.65 vs cocaine alone, OR=1.30 vs cannabis alone). Recidivist polydrug users were younger than monodrug recidivists. Over time, nearly all polydrug users transitioned to monodrug use, primarily cocaine.

Retrospective analysis of hair samples collected over 7 years by an Italian local medical committee from drug-using drivers seeking license reinstatement. 335 recidivists were analyzed. Gas chromatography-mass spectrometry tested for cocaine, opiates, and cannabis. Logistic regression identified risk factors.

Understanding which drug combinations predict impaired driving recidivism can inform license reinstatement decisions and targeted interventions. The specific identification of cocaine-cannabis as a risk combination has practical implications for monitoring programs.

The finding that cocaine-cannabis users have elevated driving recidivism risk, and that they tend to transition to cocaine-only use over time, suggests cannabis may serve as a co-use facilitator in the early stages of a pattern that becomes cocaine-dominant.

Italian regulatory context may not generalize to other countries. Hair testing detects use over weeks/months, not at the time of driving. Selection bias: only captures people who sought license reinstatement. Cannot determine if drugs were used simultaneously or at different times.