The sample of studies was generated from: (a) computerized literature searches of PsycINFO, AIDSLINE, MEDLINE, and CINAHL, using the keywords and descriptors: HIV, AIDS, STD, prevention, education, risk reduction, intervention, adolescent(s), teen(s), and youth; and (b) reference sections from empirical articles and reviews. In order to ensure confidence in the conclusions of this review, a priori criteria were established for assessing the internal validity of the individual studies. Only studies that met four inclusion criteria were included.
First, this review was limited to studies that used primarily teenage samples (mean ages ≤19 years old or, for studies that did not report the mean age, the age range was within 13 to 19 years). Second, this review included only randomized controlled trials (RCTs), the strongest design for evaluating interventions because it permits the most unbiased comparison of intervention effects, eliminates many potential threats to internal validity present in uncontrolled studies (Campbell & Stanley, 1966
), and improves the ability to infer causation to the intervention for effects observed (Mantell, DiVittis, & Auerbach, 1997
). Thus, limiting this review to only RCTs improves the level of confidence in the conclusions drawn. Third, the primary outcomes were sexual risk behaviors (e.g., frequency of unprotected sex, condom use). Interventions designed to increase rates of HIV testing were not included unless they also had specific sexual risk reduction outcomes. Finally, only studies published in peer-reviewed journals prior to September 2000 were included.
Sample of Studies
The literature search yielded 97 studies that provide data from an HIV risk reduction intervention. Eighty-eight of 97 studies (91%) met the age criteria for this review. Among these 88 studies, 67 (76%) employed a controlled design. Forty-three of the 67 controlled studies (64%) randomly assigned individuals (or other units of participants) to conditions. Of the 43 RCTs, 22 (51%) measured sexual behavior change. Twenty-two studies met all the inclusion criteria and served as the sample of studies for the present review. These studies are noted in the reference section with an asterisk (*).
The 22 studies in this review reflect the broad scope of HIV prevention in terms of the samples chosen, settings used, intervention design and content, and findings. provides extensive details regarding the study design, setting, theoretical foundation, sample characteristics, descriptions of the intervention, significant outcomes, and data analysis for all 22 studies. In the sections that follow, study populations, settings, and key findings are described.
HIV Sexual Risk Reduction Interventions with Adolescents: Randomized, Controlled Trials
Sample sizes in the studies ranged from 34 for a pilot study (St. Lawrence, Jefferson, Alleyne, & Brasfield, 1995
) to 3,869 for a large-scale school-based study (Coyle et al., 1999
). The median and mean sample size were 326 youths and 549 (SD
833) youths, respectively. Only 4 of 23 studies (17%) used a sample of less than 100. Sample characteristics, including the targeted population, are provided in , column 2.
One approach to HIV prevention is to target adolescent populations that have been identified at high-risk for HIV/STDs, such as inner-city minority youth. Studies that targeted high-risk youth identified high-risk populations based on ethnicity, location, and prior risk behavior. Seven studies were conducted exclusively with African American youth, and another seven studies had samples of more than 50% African American participants. Given the disproportionate number of African American youth infected with HIV, the finding that 64% of RCTs were conducted primarily with African American youth is, from a public health perspective, quite appropriate. Four studies reported using samples of predominately Hispanic youth, a group also at high risk for HIV. Six studies targeted minority youth who live in inner-city areas (Kipke, Boyer, & Hein, 1993
; Rotheram-Borus, Gwadz, Fernandez, & Srinivasan, 1998
; Stanton et al., 2000
; Stanton et al., 1996
; Walter & Vaughan, 1993
; Workman, Robinson, Cotler, & Harper, 1996
). In sum, 18 studies (82%) were conducted with urban minority youth; a group that has been disproportionately affected by HIV. Other high-risk youth also targeted were youth in treatment for substance dependence (St. Lawrence, Jefferson, et al., 1995
), incarcerated youth (Gillmore et al., 1997
; St. Lawrence, Crosby, Belcher, Yazdani, & Brasfield, 1999
), and youth who were abused or neglected (Slonim-Nevo, Auslander, Ozawa, & Jung, 1996
). Three studies targeted youth based on high risk behavior by conducting studies in STD clinics (DeLamater, Wagstaff, & Havens, 2000
; Metzler, Biglan, Noell, Ary, & Ochs, 2000
; Orr, Langefeld, Katz, & Caine, 1996
) because adolescent patients in STD clinics have been found to have high rates of sexual risk behaviors (e.g., Heffernan, Chiasson, & Sackoff, 1996
A second, and more general, approach to HIV prevention is to broadly target the adolescent population and thereby include youth with varying degrees of HIV risk. For example, five studies targeted adolescents from schools (Coyle et al., 1999
; Kirby, Korpi, Adivi, & Weissman, 1997
) and primary care settings (Boekeloo et al., 1999
; Gillmore et al., 1997
; Mansfield, Conroy, Emans, & Woods, 1993
). Sexually-inexperienced youth are good candidates for HIV prevention because previous research has shown that it is more difficult to achieve behavioral change in teens who have already initiated sex (Kirby et al., 1991
). Three RCTs targeted younger adolescents (10–14 years; Jemmott, Jemmott, & Fong, 1998
; Kirby et al., 1997
; Stanton et al., 1996
) and three studies had samples of predominately sexually inexperienced youth (Levy et al., 1995
; Kirby et al., 1997
; Workman et al., 1996
Thus, a clear strength of this literature is a focus on both general and high-risk adolescent populations. A broad primary prevention approach ensures that youth who are not engaging in high-risk behaviors receive prevention services before they initiate risky sex. An additional benefit is that results are generalizable to the larger adolescent population. In contrast, a targeted approach addresses the most needy groups of youth in order to make the greatest impact on reducing new cases of HIV (Kalichman, 1998
). The cost of this targeted approach is that results only can be generalized to the specific population and the intervention has less “reach.”
However, some high-risk groups are not well-represented in this literature. Only one RCT has been conducted with gay and lesbian teenagers and it also included young adults (Rotheram-Borus, Murphy, Fernandex, & Srinivasan, 1998
). This is a particularly vulnerable population given the recent increase in rates of HIV among young MSM (CDC, 2000b
). The lack of studies in this area may reflect the difficulty in identifying sources of gay and lesbian youth, and the practical difficulties of conducting a RCT in a rare setting where these youth could be identified (i.e., a gay community center) without contamination between conditions. Youth with mental illness are another vulnerable group for HIV/STDs that have not been targeted for RCT prevention studies despite elevated risk for HIV (Carey, Weinhardt, & Carey, 1995
). Prevention efforts are beginning to address HIV positive (HIV+) populations (Rotheram-Borus et al., 2001
) with goals that are consistent with primary HIV prevention (i.e., preventing new HIV infections) and secondary HIV prevention (i.e., reducing further health risks to those already infected).
Interventions were conducted in a variety of settings that can be categorized as schools, community sites, and health care settings. In school-based studies, interventions were implemented in high schools (Coyle et al., 1999
; Walter & Vaughan, 1993
), junior high schools (Kirby et al., 1997
; Levy et al., 1995
), and a parochial school (Workman et al., 1996
). These interventions were implemented as part of the school curricula and were offered to a broad range of students, consistent with a broad primary prevention approach.
The Safer Choices curriculum (Coyle et al., 1999
) illustrates how many school-based interventions are implemented and evaluated. In this study, 20 high schools were randomly assigned to receive Safer Choices (the experimental curriculum) or a standard, knowledge-based AIDS curriculum. A unique feature of this intervention was the dual focus on strategies that influenced both individual risk factors (i.e., attitudes, behavioral skills) and social environments (e.g., peer resources). The curriculum was delivered in regular classrooms by a teacher and two peer leaders over 10 class periods. Consistent with the theoretical framework, mastery experiences, role-plays, peer facilitation, and parent-teen communication were emphasized. Initial findings for 3,677 students at a 7-month follow-up showed that students who received Safer Choices reported less frequent unprotected intercourse and were more likely to have used condoms at last intercourse than students in the control curriculum.
The Safer Choices study highlights several potential advantages of school-based interventions, including access to large numbers of youth (95% of youth are enrolled in school; National Center for Education Statistics, 1997
), which allows for large-scale intervention projects that can potentially influence behavior change at the individual and peer group level (Kirby et al., 1997
), and the ability to examine behavioral change longitudinally. Schools are an ideal setting to reach sexually inexperienced youth because most teens are enrolled in school before initiating sexual activity (DiClemente, 1993
). However, limitations of school-based programs are that measuring sexual behavior is often prohibited by school districts (e.g., DiClemente et al., 1989
), and the findings cannot be generalized to out-of-school youth.
Concerns have been raised about how to improve access to HIV prevention programs for youth not enrolled in school, who often have higher rates of sexual risk behaviors (Walter & Vaughan, 1993
). Eleven interventions were conducted in community settings and provided unique access to vulnerable and difficult to reach youth. The sites included social service agencies (Rotheram-Borus, Gwadz et al., 1998
; Slonim-Nevo et al., 1996
), public housing developments (Stanton et al. 1996
; Stanton et al., 2000
), and detention centers (Gillmore et al., 1997
; St. Lawrence et al., 1999
). These sites provide access to high-risk adolescent populations, and use of intervention strategies that are tailored specifically for the needs of that population.
In addition, four RCTs were conducted in after-school settings. They differ from the school-based interventions because they were not implemented as part of the school curriculum or by teachers during regular school hours. Instead, these studies were implemented by research staff after school hours (Jemmott, Jemmott, & Fong, 1992
; Jemmott, Jemmott, Fong, & McCaffree, 1999
; Kipke et al., 1993
). The studies by Jemmott et al. (1992
) were conducted with African American youth at schools. Unlike most school-based studies, these HIV risk reduction interventions targeted a population of high-risk teens. The most comprehensive of these studies (Jemmott et al., 1998
) was conducted with 659 youth who were randomly assigned to receive an abstinence, safer sex, or health promotion intervention. In this methodologically rigorous study, the interventions were structurally similar in that they were delivered in two 4-hour sessions by an adult facilitator or two peer leaders, and included identical activities. The interventions used skills building, group discussions, videos, games, and emphasized personal responsibility. A short-term effect of the abstinence intervention was found at 3-month follow-up. The safer sex intervention demonstrated efficacy in reducing the frequency of intercourse and unprotected intercourse at 12-months compared to a control condition.
Health care settings
Sexual health settings, such as STD and family planning clinics, are uniquely suited to provide access to high-risk youth. In contrast to schools, where there is a mix of sexually active and inexperienced youth, adolescents who attend sexual health clinics have higher rates of HIV risk behaviors, STDs, and other behaviors associated with risky sex (e.g., alcohol and drug use; Metzler et al., 2000
). Many adolescents who attend public clinics face obstacles to receiving health care and prevention services (e.g., lack of health insurance). Eight (36%) RCTs were conducted in health care facilities, including STD and family planning clinics (DeLamater et al., 2000
; Gillmore et al., 1997
; Metzler et al., 2000
; Orr et al., 1996
), a health center (St. Lawrence, Brasfield et al., 1995
), hospital (Mansfield et al., 1993
), primary care office (Boekeloo et al., 1999
), and treatment facility for substance abuse (St. Lawrence, Jefferson, et al., 1995
For example, Orr et al. (1996)
recruited 209 female clients from three STD and family planning clinics, and randomly assigned them to either a behavioral intervention or a standard educational intervention. The behavioral intervention was individualized and lasted 10–20 minutes; a research assistant provided HIV/STD information, and modeled behavioral skills including condom application and negotiation skills. Control patients received STD and condom information. Six months after receiving the brief intervention, adolescents in the behavioral condition reported greater condom use than those in the education only condition.
Providing prevention services in conjunction with health care mean that teens receive interventions when their awareness of the consequences of risky sex is heightened. Also, HIV prevention programs should also reduce rates of recurrent STDs, further reducing the risk of HIV transmission (CDC, 1998b
). Disadvantages of implementing interventions in clinic settings are attrition, and the limited time available for such interventions.
Thus, a second major strength of the adolescent HIV prevention research literature is that RCTs have been conducted in multiple settings. These interventions have varied in dose, content, how they are implemented, and in outcomes. School-based studies commonly involve large sample sizes, and interventions are delivered in classrooms over multiple sessions. Community-based studies are often targeted to high-risk teens, and are implemented in small groups; they occur in a variety of locations, ranging from after-school programs to detention centers. Interventions in health care settings are more likely to be single-session, brief interventions. Together, RCTs conducted in school, community, and health care settings provide youth with valuable HIV prevention services that might not otherwise be available to them.
Intervention effects in reducing HIV risk were evaluated with one or more sexual risk behaviors, including reduced frequency of penetrative sex or unprotected sex, number of sexual partners, diagnosis of STDs, and increased condom use or abstinence. Among sexually-inexperienced youth, delay of onset of sex was also used as an outcome. provides a summary of the sexual risk reduction outcomes for each RCT at each assessment period.
Sexual Risk Behavior Outcomes of N=22 HIV Risk Reduction Interventions for Adolescents
The 22 studies evaluated 23 interventions (Gillmore et al., 1997
report findings for two samples). Of the 23 interventions, 13 (57%) achieved significant risk reduction effects. In no case did the experimental intervention do worse than the control intervention. shows the number of studies that measured each outcome variable, as well as the number of studies that reported between-condition effects. Across studies, frequency of unprotected sex was reduced in 75% of studies that measured this outcome. Condom use was improved in 53% of studies that measured this outcome. Number of partners was reduced only in 27% of studies. The lowest rates of behavior change were found for abstinence, which improved in only 14% of studies that measured it. These findings are confirmed by a recent meta-analysis of 21 studies for youth (Jemmott & Jemmott, 2000
), which found small effect sizes for each of these outcome variables. Additional outcomes were found in the 23 interventions. Reductions in the frequency of sex were achieved in 5 of 12 studies (42%) of studies. The finding that 29% of the studies that measured STD outcome reported reductions in STDs is important. Delay of sex among sexually-inexperienced youth was found in two of four studies. Reductions in sexual risk (i.e., frequency of unprotected sex, increased condom use) were achieved more often than reductions in sexual activity (i.e., frequency of sex, abstinence).
Figure 1 Sexual risk reduction outcome variables measured by 22 randomized, controlled HIV risk reduction interventions with adolescents. The direction of the variables indicates greater HIV risk reduction, such as reduced STDs, sexual partners, frequency of sex (more ...)
In summary, many adolescent HIV risk reduction interventions have been effective but are associated with small effect sizes. Characteristics of effective interventions remain unknown. Improved understanding of what factors are associated with effective interventions is most likely to occur if the methodology of research studies is enhanced. Toward the latter goal, we provide a methodological critique of extant research, and suggestions for the design of new studies.