Results from the eight analyses of alcohol or drug use and condom use showed that people who used any substances in conjunction with sex were less likely to use condoms (summary OR, 0.77; 95% CI, 0.64–0.91), with some heterogeneity in odds ratios (Q [7 df] = 11.1;P = 0.13;Figure 2). The summary odds ratio was highly influenced by a single large study 31; without this study the summary odds ratio for the remaining seven analyses was 0.90 (95% CI, 0.69–1.18).
The results of this meta-analysis showed that alcohol use was related to nonuse of condoms at first intercourse, with a trend among adolescents in general toward nonuse of condoms when drinking. Among adults, drinking was unrelated to use of condoms in sexual encounters. The first sexual experience represents a significant and novel milestone, and the factors that affect contraceptive use may not apply to subsequent events. 8 First-timers are novices at sex and probably at drinking as well, and their decisions may reflect the limited knowledge and experience one might expect of beginners. In their first sexual experiences, often with ambivalent feelings, the partners may find that the perceived power of alcohol as a sexual disinhibitor influences their decisions regarding sex and protection. Moreover, drinking, especially for those having sex for the first time, may interfere with planning, which affects the likelihood of using contraception. 26,67
The analysis suggested that using other substances, either alone or in addition to alcohol, may be associated with nonuse of condoms, but none of the reports of the individual studies reviewed gave information about what drugs were used. Alcohol has long been associated with sexual behavior in many contexts 68; therefore, it is not surprising that there have been many studies examining the relationship of alcohol use to sexual behavior in general 68,69 and unprotected sex in particular. 2 Other drugs receiving special attention in relation to sexual risk-taking are methamphetamine, 70 inhalants, 71 and crack/cocaine. 72 Not only do these drugs have different pharmacological effects but they also may be used in very different situations. For example, alcohol can be an instrument of courtship, 68 and as such is more common in encounters with new sexual partners. 24 Cocaine, according to conventional wisdom, has desirable effects on sexual performance, 73 and crack is often associated with trading sex for drugs. 74 Among homosexual men, some research has identified strong relationships between risky sex and the use of nitrites 71 or methamphetamine. 70 Differences in pharmacological effects, situations of use, and reasons for use may lead to different relations of these drugs to unprotected sex.
In the studies reviewed here, drinking with sex was analyzed as a binary measure, without reference to the amount of alcohol consumed. The effect of alcohol on behavior, from a mild energetic state to depression and coma, varies with quantity. 75 A sufficient amount of alcohol leads to depressed reflexes and decreased coordination, potentially interfering with condom use. The amount of alcohol consumed may contribute to the strong relationship of alcohol use and unprotected sex at first intercourse if the amount drunk is particularly large in these encounters. For example, in one study of adults, 36% of women and 55% of men who drank before their most recent sexual encounter with a new partner had 5 or more drinks, 76 whereas studies of first sexual encounters have shown that 54% of young women who drank before their first sexual encounter had 7 or more drinks 77 and that 75% of young men had 5 or more drinks. 67
By ensuring that alcohol use and unprotected sex are temporally paired, an event-level method strengthens causal inferences, but it does not eliminate confounding variables. For example, lifestyle factors such as a propensity for risk-taking, sensation-seeking, or unconventionality might lead to both alcohol use and unprotected sex in these events. Therefore, a link between drinking and unprotected sex in first sexual encounters might represent these lifestyle factors rather than a causal effect of alcohol. 2,78
A cause–effect model and a lifestyle model have different implications for prevention and education. Prevention programs that assume a causal effect of alcohol on risky sex might be ineffective if drinking and risky sex are linked through lifestyle factors. 78 Health education messages that are based on a causal model may even have paradoxical harmful effects, if highlighting a link between drinking and risky sex gives people a convenient excuse for engaging in risky behaviors. 2,79 Moreover, a general message that alcohol leads to sexual risk behavior is misleading, given that this link is found only at first intercourse, where drinking seems entangled with ambivalent feelings and lack of planning. Incorporating these complex relations into education programs for adolescents is a challenging task. 79
The interplay between alcohol use and sexual behavior is part of a context that incorporates elements of personality, situation, and relationships. 26,78 Alcohol use is more common in sexual encounters between casual partners than in encounters involving primary partners, 19,20,23,24 and most people who report drinking in a sexual encounter report that their sexual partner was drinking as well. 24,77 Some findings suggest that drinking is related to unprotected sex for casual sexual partners and not primary partners 49,59 or that alcohol affects sexual activity only at certain points in a relationship. 8 The major finding of this meta-analysis—that drinking is related to unprotected sex only in first sexual encounters—highlights the importance of the context of the sexual encounter in influencing both drinking and sexual behavior.
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