Genetic predisposition to alcohol and nicotine may be closely related, according to animal studies conducted by Canadian researchers.

Researchers funded by the National Institute on Alcohol Abuse and Alcoholism bred rats that were genetically predisposed to alcohol use ("P" rats) and compared them to another strain bred not to like alcohol ("NP" rats). They found that the P rats self-administered twice as much nicotine by pressing a lever as the NP rats.

"Our findings suggest that the genetic factor underlying the high alcohol consumption seen in P rats may also contribute to their affinity for nicotine," said lead author A.D. Lê, Ph.D.

Alcoholics are three times as likely as non-alcoholics to smoke. The rat study was particularly valuable because the animals were given the chance to administer nicotine before they were exposed to alcohol, mitigating against the hypothesis that alcohol use itself leads to smoking.

The P rats did not demonstrate any excess preference for other drugs, such as cocaine.

The research was published in the February 2006 issue of the Journal of Neuroscience.