Personal and perceived peer norms that encourage adolescents to refrain from sex are associated with reduced odds of sexual initiation among seventh and eighth graders (odds ratios, 0.8 and 0.7, respectively). According to data from a longitudinal survey conducted in three inner-city school districts in New Jersey,1 alcohol and drug users are more likely than nonusers to start having sex in these grades (1.3-1.5). In addition, the greater adolescents' sense of self-efficacy in avoiding risky behavior and using condoms, the less likely they are to start having sex in seventh grade (0.9), but unexpectedly, the more likely they are to initiate sex in eighth grade (1.2).
Analyses were based on survey data from middle school students who participated in an HIV intervention program in 1994-1996. Participants completed baseline surveys at the beginning of seventh grade and were surveyed again at the end of seventh grade and at the end of eighth grade. Questionnaires asked adolescents about their sexual behavior, demographic characteristics and academic achievement, which was categorized as high (A's and B's), average (B's and C's) or low (C's, D's and F's). The surveys also covered a range of psychosocial factors, including personal and perceived peer norms about refraining from sex and about condom use; communication with parents; self-efficacy in refusing sex, drugs or alcohol and in using condoms; alcohol and drug use in the last 30 days; perceived barriers to condom use; and perceived risk of acquiring HIV or another sexually transmitted disease (STD). Psychosocial survey items were grouped by category, scaled and converted to continuous standard scores. Participants who were sexually experienced at baseline or who provided incomplete or contradictory responses were eliminated from the sample, and adolescents who reported that they had initiated sex during seventh grade were excluded from the analyses of initiation in eighth grade.
Of the 2,973 participants who completed baseline surveys, 48% were male and 52% were female; 84% were aged 12-13. Fifty-one percent of students were black, 30% Hispanic, 9% white, 3% Asian and 6% members of other racial or ethnic groups. At enrollment, 13% of young women and 39% of young men reported that they had already had sex.
By the end of seventh grade, 13% of the 1,637 adolescents who remained in the sample reported that they had become sexually experienced. Although no statistical tests were performed to evaluate the significance of variations, the proportions appeared to be higher among some demographic groups than among others: 19% of men vs. 9% of women; 16% of low academic achievers vs. 10% of high achievers; 16% of blacks and 12% of Hispanics vs. 7% of whites, Asians and other ethnic groups; and 16% of those who spoke only En-glish at home vs. 10% of those who spoke another language. At the end of eighth grade, 15% of the remaining 1,524 participants reported that they had started having sex since the last assessment, and similar differences emerged among demographic groups.
To identify independent predictors of sexual initiation, the researchers constructed three logistic regression models for each time period studied. The first model assessed psychosocial factors, the second considered only demographic characteristics and the third combined those variables that were statistically significant in the first two models.
At the end of seventh grade, the psychosocial model revealed three significant predictors of sexual initiation: Adolescents' odds of having had sex at this stage decreased as their own beliefs, or their perceptions of friends' beliefs, that one should refrain from sexual intercourse increased (odds ratio, 0.7), and as perceived self-efficacy in using condoms and refusing sex increased (0.8). Alcohol and drug users had higher odds of sexual initiation than nonusers (1.2). When only demographic factors were considered, the odds of sexual initiation during seventh grade were significantly higher among men than among women (3.0), and among low and average academic achievers than among high achievers (1.7 and 1.4, respectively); odds were lower among adolescents who spoke another language at home than among English-only speakers (0.6), and lower among Hispanics (0.9) and whites, Asians and others (0.4) than among blacks.
Scoring high on peer norms remained a highly significant psychosocial factor in the combined model: More preventive norms about refraining from sex were associated with decreased odds of sexual initiation (odds ratio, 0.8). Findings in this model were also consistent for self-efficacy (0.9) and alcohol and drug use (1.3). Gender remained the most significant predictor among the demographic variables; men's odds of having initiated sex were more than twice those of women (2.5). The odds of sexual initiation were lower among adolescents who spoke another language at home than among English-only speakers (0.5) and among whites, Asians and others than among blacks (0.5). In the combined model, Hispanic ethnicity and academic achievement levels were not associated with adolescents' likelihood of having initiated sex during the first phase of the study.
At the end of eighth grade, results of the psychosocial model again revealed a strong association between preventive sex norms and reduced odds of sexual initiation (odds ratio, 0.7). Alcohol and drug use, barriers to condom use and perceived risk of STDs and HIV were linked to elevated odds of sexual initiation during eighth grade (1.2-1.4). Unexpectedly, high levels of self-efficacy were also associated with increased odds of sexual initiation at this stage (1.2). The analysis of demographic variables indicated that predictors for eighth grade were similar to those found for seventh grade: male gender, black race and low or average academic achievement. In addition, sexual initiation was less likely among adolescents whose mothers had graduated from high school or college than among those with less educated mothers (0.9 and 0.8, respectively).
In the combined model, the higher adolescents scored on sex norms, the less likely they were to have become sexually active in eighth grade (odds ratio, 0.7). Participants who reported alcohol or drug use were more likely than nonusers to report that they had initiated sex (1.5); barriers to condom use and high levels of perceived risk were also associated with increased odds of sexual initiation (1.3 and 1.2, respectively). As in the psychosocial model, adolescents' odds of sexual initiation increased with self-efficacy scores (1.2). Most demographic variables remained statistically significant: Sexual initiation was more likely to occur among men than among women (1.5), and among low and average academic achievers than among high achievers (1.7 and 1.5, respectively); the odds were lower among Hispanics (0.4) and among whites, Asians and other ethnic groups (0.4) than among blacks.
The researchers note that young adolescents' level of cognitive development may have limited their ability to understand and answer certain survey questions. For example, participants' failure to distinguish well between self-efficacy in refusing risky behaviors and in using condoms led to the grouping of these items in a single variable; the mixed findings on self-efficacy should thus be interpreted with caution. The researchers conclude that their findings support "program efforts which address adolescent personal and perceived norms about refraining from sexual intercourse and which address alcohol and drug use among youth."
1. Santelli JS et al., Initiation of sexual intercourse among middle school adolescents: the influence of psychosocial factors, Journal of Adolescent Health, 2004, 34(3): 200-208.