Addictive drugs can profoundly affect social behaviour both acutely and in the long-term. Effects range from the artificial
sociability imbued by various intoxicating agents to the depressed and socially withdrawn state frequently observed in chronic
drug users. Understanding such effects is of great potential significance in addiction neurobiology. In this review we focus on
the ‘social neuropeptide’ oxytocin and its possible role in acute and long-term effects of commonly used drugs.

Oxytocin regulates social affiliation and social recognition in many species and modulates anxiety, mood and aggression. Recent
evidence suggests that popular party drugs such as MDMA and gamma-hydroxybutyrate (GHB) may preferentially activate
brain oxytocin systems to produce their characteristic prosocial and prosexual effects. Oxytocin interacts with the mesolimbic
dopamine system to facilitate sexual and social behaviour, and this oxytocin-dopamine interaction may also influence the
acquisition and expression of drug-seeking behaviour. An increasing body of evidence from animal models suggests that even
brief exposure to drugs such as MDMA, cannabinoids, methamphetamine and phencyclidine can cause long lasting deficits in
social behaviour. We discuss preliminary evidence that these adverse effects may reflect long-term neuroadaptations in brain
oxytocin systems. Laboratory studies and preliminary clinical studies also indicate that raising brain oxytocin levels may
ameliorate acute drug withdrawal symptoms. It is concluded that oxytocin may play an important, yet largely unexplored, role
in drug addiction. Greater understanding of this role may ultimately lead to novel therapeutics for addiction that can improve
mood and facilitate the recovery of persons with drug use disorders.
British Journal of Pharmacology (2008) 154, 358–368; doi:10.1038/bjp.2008.132

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