Neurological aspects of drug misuse

The misuse of illicit drugs and prescription medications may cause neurological complications from overdose, withdrawal and long-term chronic misuse. Drug-use disorder has become particularly important and complex because of different patterns of presentation associated with new psychoactive substances and the growing misuse of opioids, synthetic cannabinoids and stimulants. We review worldwide demographic data of drug-use disorder and discuss the individual classes of agents, newer developments relating to understanding the mechanisms of action and the patterns of administration, usage, toxicity and withdrawal. We consider the difficulties in assessment and the specific acute syndromes of toxicity that present with neurological manifestations. We review the neurological patterns of longer-term complications and consider the effects of drug misuse-related trauma, infection, seizures, stroke, toxic leucoencephalopathy, cognitive impairment, movement disorders and neuromuscular complications. The neurological consequences of drug-use disorder disproportionately affect the young and can have devastating effects on innocent lives. It is essential that neurologists recognise acute toxicity early and understand the longer-term consequences of drug-use disorder.