The slogan "Hugs, Not Drugs" now has some added scientific weight.
The subjects of the study were prairie voles, not humans - though that's not reason to automatically dismiss the findings. Prairie voles have long been used as an animal model for human relationships. Like humans, they tend to form long-term, often life-long pair bonds (though, also like humans, they sometimes cheat). Pairs commonly carry on like newlyweds, cuddling and grooming each other, and they build a life together of shared domestic and child-rearing responsibilities.
Researchers at Florida State University decided to investigate whether relationship status influenced how male prairie voles responded to the highly addictive drug methamphetamine. They introduced the drug both to prairie voles who still were virgins, and not yet bonded with a partner, and to prairie voles who had established a (mostly) monogamous relationship.
The pair-bonded prairie voles were less interested in the drug in general. Only the unbonded virgins were willing to spend time in a frightening cage to gain access to the methamphetamine. (Not a bad comparison for the human counterpart of hanging around a sketchy neighborhood to score.)
Then the researchers looked at how the brains of the prairie voles responded to direct administration of the drug. The brains of the unbonded voles responded enthusiastically, increasing the activity of dopamine in the nucleus accumbens. Dopamine release in this region is known to be a key mechanism by which a substance - be it alcohol, nicotine, cocaine, or food - becomes addictive. But the opposite happened in the brains of bonded voles. Their dopamine receptors became less responsive. It was almost as if the brain was protecting itself against the risk of addiction. Previous research has shown that dopamine plays a critical role in the formation of prairie vole pair bonds; mating is like a drug in itself, and possibly one that forever shapes which rewards the brain responds to.
What are the implications for humans? I'm pretty sure it's not to make sure all the young male virgins get laid, though I suppose that's not an impossible conclusion from this data. The researchers suggest a different take - that social bonds may reduce the risk of addiction, especially the supportive bonds found in long-term relationships. This is consistent with previous human research, which has shown that both perceived social support and adult attachment style - how secure you feel in close relationships- predict lifetime prevalence of substance abuse. The less social support and less relationship security, the greater the risk of addiction.
So: Hugs, not drugs? Sounds good to me; at the least, it might make it easier to "Just Say No."
Aragona BJ et al. (2003). A critical role for nucleus accumbens dopamine in partner-preference formation in male prairie voles. The Journal of Neuroscience, 23, 3483-90.
Caspers KM et al (2005). Contributions of attachment style and perceived social support to lifetime use of illicit substances. Addictive Behaviors 30, 1007-11.
Lui Y et al. (2011). Social bonding decreases the rewarding properties of amphetamine through a dopamine D1 receptor-mediated mechanism. The Journal of Neuroscience, 31, 7960-66.