National Drug Strategy
National Drug Strategy

Comorbidity of mental disorders and substance use: a brief guide for the primary care clinician

12.3 Does substance use predispose individuals to brain injury?

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Substance use (including alcohol, cannabis and other illicit substances) has been associated with brain injury. Up to 40% of individuals with a brain injury have been found to meet DSM-IV criteria for substance use disorders prior to the injury. Conversely, 68% of people with a substance use disorder have also been found to have had some sort of previous head injury(503, 504).

While there is a strong relationship between substance use and brain injury, the order of causality remains unclear(504-506). Some debate also remains as to whether substance use or its severity is an actual predictor of brain injury(507, 508).

The risk of brain injury as a result of increased impulsivity and risk taking or novelty seeking behaviour associated with underlying personality traits may be exacerbated by substance use. Combined with low harm avoidance, this increased impulsivity can result in head trauma from falls or accidents or unintentional overdose(2, 501).

Substance dependence may result in attempted suicide due to the inability to cope with the negative consequences of such dependence(351, 501, 507, 509).

Brain injury can also result from:

Patients with brain injury and alcohol use disorders have been shown to have significantly reduced grey matter volumes compared with brain injured patients without alcohol use disorders(508). The question is whether an initial brain injury predisposes people to an increased risk of subsequent alcohol or other substance-induced brain injury.

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