9.1.1 Effects of long-term alcohol use and other substance use on driving
Chronic heavy alcohol use carries a real risk of neurocognitive deficits relevant to driving capability including:
- short-term memory and learning impairments, which become more evident as the difficulty of the task increases
- impaired perceptual-motor speed
- impaired visual search and scanning strategies
- deficits in executive functions such as: mental flexibility and problem-solving skills; planning, organising and prioritising tasks; focusing attention, sustaining focus and shifting focus from one task to another; filtering out distractions; monitoring and regulating self-action; or impulsivity.
Long-term heavy alcohol use is also associated with various end-organ pathologies that may affect ability to drive, for example, Wernicke- Korsakoff syndrome or peripheral neuropathies experienced as numbness or paresthesia of the hands or feet. In the event of end-organ effects relevant to driving, the appropriate requirements should be applied as set out elsewhere in this publication.
Alcohol-dependent people may experience a withdrawal syndrome on cessation or significant reduction of intake, which carries some risk of generalised seizure (refer to Acute symptomatic seizures text and standards), confusional states and hallucinations.
Substances (prescribed, over-the-counter and illicit) are misused for their intoxicating, sedative or euphoric effects. Drivers under the influence of these drugs are more likely to behave in a manner incompatible with safe driving. This may involve, but not be limited to, risk taking, aggression, feelings of invulnerability, narrowed attention, altered arousal states and poor judgement.
Illicit substances are a heterogeneous group. Chronic effects of their use vary and are not as well understood as those of alcohol. Some evidence suggests cognitive impairment is associated with chronic stimulant, opioid and benzodiazepine use. Illicit substance users may be at risk of brain injury through hypoxic overdose, trauma or chronic illness.
End-organ damage, including cardiac, neurological and hepatic damage, may be associated with some forms of illicit substance use, particularly injection drug use. Cocaine and other stimulant misuse have been linked with cardiovascular pathology. In the event of end-organ effects relevant to driving, the appropriate requirements should be applied as set out elsewhere in this publication.1–4