Genetic factors play a significant role and are estimated to account for about half of overall addiction risk, varying across the lifespan and with different substances.

Genes involved in the metabolism of drugs, in dopaminergic and glutamatergic neurotransmission, in neuroplasticity, and in brain development are all thought to be involved.

Psychiatric disorders such as mood, anxiety, psychotic and personality disorders, and ADHD are also associated with a higher risk of substance use disorder – and the association is thought to be bidirectional.^4,6