Sneaky cheaters are also unsafe sex partners. For those who were unfaithful not only were they practicing risky sexual activities chances are alcohol and drugs were also involved.

For those in a relationship, sexual health is important and some may seek sex outside of the relationship. At times this is consensual, with both partners being able to have sexual partners outside of the relationship and other times a partner may be sneaking off without consent. Those who engaged in this type of behavior were found to be quite the risky sexual partner.

The study uncovering the risky behavior of cheating individuals was led by Terri D. Conley, PhD, from the Department of Psychology at the University of Michigan. A total number of 1,647 people responded to an online ad in regards to their sexual activity. Of this group, 801 people had sex with someone who was not their primary partner and in this group, 493 had the consent of their partner, an open relationship, while 308 were in a monogamous relationship but were cheating on their primary partner.

The researchers that people who were cheating used condoms for vaginal or anal sex less often than people who had sexual partners as part of an open relationship.  Condom use for vaginal sex was 27 percent lower for cheaters and condom use for anal sex was 35 percent lower for cheaters when compared to other individuals who had sexual partners as part of an open relationship.

While lower condom use is already a problematic behavior, drug and alcohol use was found to be higher in cheaters than in individuals who had sexual partners with the consent of their partner. According to researchers, drug and alcohol use was 64 percent higher in unfaithful individuals when compared to individuals in an open relationship.

The researchers believe these risky behaviors increase the risk of sexually transmitted infections (STI) for those who are being unfaithful in their monogamous relationship. Being in a committed relationship with just one partner can be quite beneficial in preventing STI's, note researchers, as long as they have tested negative for STI's at the beginning of the relationship and remain faithful to one another throughout the relationship.

The researchers conclude that more education is needed to raise awareness of STI's and promote condom use. Cheating can do more than just ruin a relationship as it could also increase the risk of STI's.

The study was published in The Journal of Sexual Medicine.