Alcohol increases desire for sex without condoms: systematic review

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Alcohol consumption has an impact on the intention of individuals to have unprotected sex, according to the results of a systematic review and meta-analysis published in the journal Addiction.

“The higher the blood alcohol content, the more pronounced the intention to engage in unsafe sex,” comment the investigators.

Alcohol can lead to disinhibition, affect cognitive capacity, and has an impact on immune function. But a direct relationship between alcohol and the transmission of HIV and other infections is difficult to prove conclusively. This may be because people who consume alcohol may be more likely to have unprotected sex because they generally lead riskier lives.



When the statistical data from all studies which relate to a particular research question and conform to a pre-determined selection criteria are pooled and analysed together.


In discussions of consent for medical treatment, the ability of a person to make a decision for themselves and understand its implications. Young children, people who are unconscious and some people with mental health problems may lack capacity. In the context of health services, the staff and resources that are available for patient care.

inclusion criteria

The conditions which a person must meet to join a research study.



Confounding exists if the true association between one factor (Factor A) and an outcome is obscured because there is a second factor (Factor B) which is associated with both Factor A and the outcome. Confounding is often a problem in observational studies when the characteristics of people in one group differ from the characteristics of people in another group. When confounding factors are known they can be measured and controlled for (see ‘multivariable analysis’), but some confounding factors are likely to be unknown or unmeasured. This can lead to biased results. Confounding is not usually a problem in randomised controlled trials. 


When the estimate from a study differs systematically from the true state of affairs because of a feature of the design or conduct of the study.

One way of overcoming this limitation is to examine the relationship between blood alcohol levels and self-reported intention to use a condom or engage in unprotected sex.

Investigators from Canada therefore performed a systematic review and meta-analysis, identifying randomised studies that explored the relationship between alcohol consumption and sexual behaviour.

To be included in the analysis the studies had to satisfy five criteria:

  • Original research published in a peer-reviewed journal.
  • Individuals were randomised to receive differing doses of alcohol.
  • The intention to engage in unprotected sex was analysed.
  • The association between blood alcohol level and intention to engage in risky sex was tested.
  • Individuals were assessed individually.

The twelve studies that met the inclusion criteria were conducted in the US between 2004 and 2010. All included young adults (mean age 23 to 27 years) recruited in college or community settings.

There was a consistent relationship between blood alcohol content and intention to engage in unprotected sex.

An increase in blood alcohol content of 0.1mg/ml (compared to a content of 0.0mg/ml) was associated with a 5% increase (95% CI, 2.8-7.1%) in the likelihood of having unsafe sex.

The investigators adjusted their results to take account of publication bias and other potentially confounding factors.

A clear relationship between alcohol consumption and intention to engage in unprotected sex remained apparent, with each 0.1 mg/ml increase in blood alcohol consumption increasing the likelihood of reporting an intention to have unprotected sex by 3% (95% CI, 2.0-3.9%).

“In experimental studies there is a consistent significant effect of the level of alcohol consumption on intention to use condoms, indicating that the higher the blood alcohol content, the higher the intention to engage in unsafe sex,” comment the authors.

However, they acknowledge that their study has a number of limitations: “Most importantly, this investigation does not focus on actual condom use, but instead examines the intentions to use condoms.”

Nevertheless, the investigators believe that their study is an important addition to the literature on alcohol use and the transmission of HIV and other sexually transmitted infections.

“We found evidence of potential pathways explaining this association,” write the researchers. “Alcohol impacted on intentions about unsafe sex with a clear dose-response relationship. This may, in part, be explained by its effect on cognitive functioning.”

The authors also believe their findings have public health implications and suggest “studies varying alcohol consumption experimentally using proven effective interventions in at risk groups with later measurement of incidence of HIV and sexually transmitted infections would be advisable.”


Rehm J et al. Alcohol consumption and the intention to engage in unprotected sex: systematic review and meta-analysis of experimental studies. Addiction, 107, 51-59, 2011 (click here for the free abstract).