How much alcohol a person drinks directly affects how likely they are to have unsafe sex, a new review shows.
On average, every 0.1 milligram per milliliter increase in study participants' blood alcohol levels raised their likelihood of having unprotected sex by 5 percent, the researchers found.
Canadian researchers looked at 12 studies that examined the link between people's blood alcohol content (BAC) and how likely they were to say they would use a condom during intercourse. In all of the experiments, researchers had split the study participants into two groups, and asked one group consume alcohol, while the other group did not drink. Participants were then reported whether they would engage in unsafe sex.
The findings help explain why people who've been drinking engage in unsafe sex despite knowing better, study researcher Jürgen Rehm, the director of the Social and Epidemiological Research at Canada's Centre for Addiction and Mental Health, said in a statement. "Alcohol is influencing their decision processes."
Drinking and sex
Inall of the 12 studies that the researchers reviewed, the more alcohol participants consumed, the higher their willingness to engage in unsafe sex, according to the analysis.
This link between the role of alcohol consumption and risky sex intentions can be applied to better understanding important public health issues, such as the transmission of HIV and other sexually transmitted infections, according to the researchers.
"Drinking has a causal effect on the likelihood to engage in unsafe sex, and thus should be included as a major factor in preventive efforts for HIV," Rehm said.
Self-reporting of unsafe sex
Because the participants reported their own likeliness of having sex without a condom, there is the potential for bias, or underreporting regarding participants' willingness to have unprotected sex.
The researchers noted that not all studies that have examined this link have been published, and after they accounted for this, the increased likelihood of having sexafter drinking may be only 3 percent.
The results, which will be published in the January 2012 issue of the journal Addiction, should be taken into account in HIV/AIDS prevention programs, because efforts to reduce drinking may also lower the chance of engaging in unsafe sex, thereby reducing the number of new HIV infections, according to the study.
Pass it on: Drinking alcohol may directly affect a person's intention to have unprotected sex.
Live Science newsletter
Stay up to date on the latest science news by signing up for our Essentials newsletter.