New research indicates that having multiple sexual partners leads to an increased risk of becoming addicted to drugs or alcohol. The effect is true for men and women, but more so for the latter. The researchers speculate that there may be several explanations for the connection, among them impulsivity, which can increase risky behavior of any type. The Study To investigate the link between sexual partners and substance abuse, researchers from the University of Otago in New Zealand followed nearly all of the children born in the town of Dunedin, New Zealand, between 1972 and 1973. This included just over 1,000 people. They were tracked and interviewed several times over the years, up to the age of 32. The results of the study, which included asking the participants about their sexual partners and their use of drugs and alcohol, were published in February 2013 in the journal Archives of Sexual Behavior. The Results The strongest link between the number of sexual partners of a participant and later drug abuse occurred in the women in the study. Those women who had more than two or three sexual partners while they were between the ages of 18 and 20 were at a 10 times greater risk of developing a substance abuse problem by the age of 21. A problem with alcohol or with marijuana was most common. Women with more than two or three partners while between the ages of 21 and 25 saw a sevenfold increase in the risk of developing substance abuse by age 26. By the age of 32, the women in the study who had more than two or three partners from 26 to 31 increased their risk of having a substance abuse problem 18 times compared to those women with fewer sexual partners. For the male participants in the study, the risk of substance abuse was also increased with higher numbers of sexual partners, but not by nearly as much as it was for women. For instance, men with multiple sexual partners between the ages of 18 and 20 were just three times more likely to develop drug or alcohol problems at age 21, as compared to 10 times for women. The results of the study were adjusted to take into account mental illnesses and socioeconomic status and any affect these factors may have had on drug and alcohol abuse. The researchers found that the results held up even after controlling for these other factors. The Implications The results may not be entirely surprising, but they are important. While the study focused on one town in New Zealand, the results can apply to most people in most places. In the United States, according to the Centers for Disease Control and Prevention, nearly one-quarter of women between the ages of 20 and 24 has had two or more sexual partners. As women tend to underreport, this number could be higher. This means that a significant portion of the population is at risk for substance abuse. The study authors had a few possible explanations for the results of the research. The first and most obvious is that the link exists simply because both having multiple sexual partners and drug and alcohol use are risky behaviors. Someone who engages in one kind of risky behavior is likely to engage in another. The personality trait behind these behaviors is impulsivity. Someone who is impulsive, or acts without thinking, is likely to engage in any kind of risky behavior. This could help to explain why the results were higher for women. Having multiple partners is more taboo for women; hence it is more of a risky behavior than it is for men. Another possible explanation suggested by the researchers is that engaging in multiple, short-term, impersonal relationships may cause psychological damage, which, in turn, could lead to substance abuse as a way of self-medicating. Having multiple relationships that fail may also lead to anxiety about relationships and starting new ones--another reason to self-medicate. Women may be at greater risk in this scenario because they are culturally expected to seek out and be successful in long-term, monogamous relationships.