Ten years of longitudinal research on U.S. adolescent sexual behavior: Developmental correlates of sexual intercourse, and the importance of age, gender and ethnic background
Introduction
In the last few decades researchers examining the development of adolescent sexuality have generally focused on the risks and problems associated with sexual behaviors, such as sexually transmitted infections and pregnancy. Most of these have been cross-sectional studies designed to identify the correlates of adolescent sexual behavior. Yet, in the past 10 years, two notable features have been witnessed. First, recent perspectives in adolescent psychology have considered the risks along with the potentially positive aspects of sexuality in middle or late adolescence and emerging adulthood (Blythe and Rosenthal, 2000, Russell, 2005, Smiler et al., 2005), noting that during the teenage years, most adolescents in Western cultures become sexually active. The majority of young people have first sexual intercourse before graduating from high school, with over 60% and closer to 70% of U.S. adolescents engaging in sexual intercourse by age 18 (Carver et al., 2004, Grunbaum et al., 2002, Grunbaum et al., 2004); most of these first sexual interactions are with the other sex (Horne and Zimmer-Gembeck, 2005, Savin-Williams and Diamond, 2004). In later adolescence sexual behavior is fairly widespread—even normative.
Second, in the last 10 years, reports from a large number of longitudinal studies have been published. In these studies, various aspects of sexual behavior have been investigated, focusing on sexual perceptions and attitudes, as well as the occurrence of sexual behaviors, such as the onset of sexual intercourse. Prospective longitudinal studies were needed to disentangle the factors that were in place prior to sexual behavior from those that emerged at the same time or after the onset of sexual intercourse. For example, in some of these longitudinal studies, researchers have found that relatively earlier onset of sexual intercourse covaries with certain prior social environmental factors, such as features of family and peer relationships (e.g., Crockett et al., 1996, McBride et al., 2003, Whitbeck et al., 1999). Moreover, longitudinal studies are essential to the identification of normative and nonnormative antecedent and concurrent correlates of first sexual intercourse at different ages.
Given that so many longitudinal studies have come of age in the last decade, the associated escalation in the number of published longitudinal studies, and the expanding focus on both risky sexual behavior and positive sexuality development during adolescence, it was the ideal time for a systematic and integrative review. This review was undertaken to provide a summary of what is known about the factors that precede and covary with the onset of adolescent sexual intercourse. Because the study of age and sexual behavior is limited to correlational research, longitudinal studies or studies with intensive repeated collection of data are the best options for establishing temporal ordering. Such temporal ordering is one criterion for establishing cause-and-effect relationships (Baltes, Reese, & Nesselroade, 1988). This type of review is especially important for those considering future longitudinal research, which is costly and time consuming for both researchers and their participants. Additionally, this review provides a needed overview of what is currently known for those seeking to develop new or modify existing programs to improve the individual and social lives of young people.
In addition to providing stronger evidence of temporal ordering, such a review of longitudinal studies also could determine whether there is evidence for different groupings of correlates that may account for adolescent sexual behavior. In the current review, we refer to groupings of antecedent and concurrent (and/or distal and proximal) sexual behavior correlates as “pathways” for simplicity. Hence, pathway refers to a set of pre-existing and concurrent factors that is associated with sexual intercourse.
The complexity of adolescent sexuality has made it difficult to develop a comprehensive theoretical framework to guide research. This means that researchers have drawn from a range of theoretical perspectives or models. For example, both Problem Behavior Theory (Jessor and Jessor, 1977, Jessor et al., 1995) and Social Control Theory (Hirschi, 1969) have been used to guide some longitudinal research on adolescent sexual behavior.
In Problem Behavior Theory (Jessor and Jessor, 1977, Jessor et al., 1995), the focus is placed on individuals’ unconventional attitudes or traits and social bonds. Hence, sexual intercourse has been expected and found to be more common among young people with certain unconventional dispositional traits and among those who are relatively lacking in social bonds to conventional institutions (e.g., Capaldi et al., 1996, Goodson et al., 1997, Jessor and Jessor, 1977, Kirby, 2002). Because of these linkages between sexual behavior, individual dispositions (e.g., unconventional attitudes) and lack of social bonds, adolescent sexual behavior has been expected to covary with other problem behavior, including such behaviors as alcohol use, aggression, and delinquency. In multiple longitudinal studies reviewed here, researchers have developed hypotheses by starting with this position and studies have been designed to examine factors associated with risky adolescent sexual behaviors (e.g., Brook et al., 2004, Capaldi et al., 1996, Raffaelli and Crockett, 2003, Tubman et al., 1996a, Tubman et al., 1996b). In these longitudinal studies, the focus often has been on early sexual debut (e.g., defined in many studies as by about age 15; Bingham and Crockett, 1996, Crockett et al., 1996, Meschke et al., 2000). Regarding the antecedents or correlates of adolescent sexual intercourse patterns, the influences of other problem behaviors and family socialization have been highlighted. This, again, reflects the focus on unconventionality and lack of bonds to conventional institutions that pervades this literature.
Social Control Theory (Hirschi, 1969) starts with the assumption that most people will engage in deviant behavior and close bonds to conventional social institutions, especially family, school and church, are the factors that control deviant behaviors. Sexual behavior, especially among young adolescents, has been considered one of these deviant behaviors. Close connections to school and religious organizations, and attachment to organized activities have been expected to reflect conventional bonds that deflect deviance and shape adolescents’ values and attitudes toward delaying sexual activity.
Other researchers have had the primary aim of improving public health, which often has the goal of understanding and improving adolescent behavior, including unprotected sexual intercourse. For example, in some studies, the aims have been to understand adolescent sexual planning and decision-making in order to guide the development of better interventions to assist adolescents to delay sexual intercourse, improve condom use or limit their number of sexual partners (e.g., Hutchinson et al., 2003, McNeely et al., 2002, Sieving et al., 2000).
Finally, another perspective on adolescent sexual behavior has been described in longitudinal studies that have placed more weight on adolescent sexuality as part of normal development, while also emphasizing the importance of individual dispositions and social environments. In these investigations, researchers have emphasized the importance of biological unfolding. In what could be called a Biosocial Model (Smith et al., 1985, Udry, 1988) and extensions on this model (Rodgers & Rowe, 1993), sexual activity, unlike delinquent behavior, has been described as an activity almost every person will engage in by young adulthood and includes behaviors that are likely to continue throughout much of the life course. Because of the normative biological and relational aspects of sexual behavior, researchers with this perspective have acknowledged the importance of biological factors, such as hormones and physical maturation, and social factors related to maturation, such as dating, that may promote the onset and patterns of sexual behavior during adolescence. For example, young people who appear more physically mature seem to prompt certain responses from the social environment resulting in increased opportunities for romantic and sexual involvement (Brooks-Gunn and Paikoff, 1997, Graber et al., 1998). Extensions of this model emphasize development and biology within a context of social contagion—the spreading of ideas and activities within a social environment at times of transition—to explain adolescent sexual behavior (Rodgers & Rowe, 1993).
None of these theories and perspectives includes an explicit description of different pathways associated with adolescent sexual behavior. However, these theories do not preclude the possibility of multiple pathways. In addition, when these various theories are simultaneously considered along with other related areas of research and theory on the development of adolescent behavior (e.g., Moffitt’s theory of antisocial behavior, 1993), there could be at least two correlational pathways associated with sexually intercourse onset before the age of 18. One pathway would include certain dispositional traits marked by unconventionality, problem behaviors, and lack of social bonds to family, school or other social institutions. A second pathway might include certain biological characteristics (e.g., earlier maturation, particular hormonal levels or patterns), some problem behavior at a lower and more common level than the other group (e.g., experimentation with alcohol, other minor delinquent acts) and, because popularity with peers has been associated with earlier dating (Feldman et al., 1995, Franzoi et al., 1994), peer group success. The first pathway would be more likely found when onset of sexual intercourse is most deviant from the norm and the most risky, such as very early onset of sexual intercourse. The second pathway would be more representative of a typical adolescent and found when onset of sexual intercourse occurs at an age when it is more typical (i.e., when a larger proportion of adolescents initiate sexual intercourse). This suggests that two pathways could be identified when studies of early onset of sexual intercourse (often defined as before age 14 or 15) are separated from those that also examine correlates of onset closer to what is average or typical in the U.S. (ages 16–18). One purpose of the current review was to organize studies in this way in order to illuminate whether multiple pathways may be present. Encouraging findings could direct future research toward confirming multiple pathways.
The possibility of two pathways associated with adolescent sexual behavior is quite consistent with Moffitt’s (1993) theory that knowing age of onset of antisocial behavior among adolescents would identify two different pathways to membership into what had historically been studied as one group of antisocial adolescents. This one group was expected to share certain developmental histories and have a common set of factors associated with the onset, continuation, and escalation of their problem behaviors. Moffitt proposed that antisocial adolescents could be differentiated into two groups with differing developmental histories and different age of onset (early versus later) of antisocial behavior. Because of the strong evidence of covariation between sexual behavior and antisocial behavior (usually defined to include alcohol and other drug use, delinquent acts, and aggression), Moffitt’s theory provided a foundation for our expectation of two pathways to adolescent sexual behavior and how these groups might be identified after grouping adolescents by age of sexual intercourse onset.
There are other theories that do not preclude the possibility of two correlational pathways associated with adolescent sexual behavior. These theories include the biopsychosocial health model that integrates biology, psychological factors and environmental experiences (Weiss, 2000), the life-span developmental perspective (Baltes, Reese, & Lipsitt, 1980), and the stage termination model of development (Peskin, 1973; see also Bingham & Crockett, 1996). Each of these models identifies behavior as impacted by the dispositions and biological development of the individual, as well as being shaped by the environment via learning, modeling, and opportunities. Influential environments include those at the more proximal level of the family, close dyadic relations, and the friendship group, and also include the broader contexts, for example, of the peer group, school, neighborhood, cultural and religious structures, and government policies. Adolescent may report similar behavior, but they may have experienced different combinations of individual and environmental experiences that partially account for or covary with their behaviors. Adding to this, each model points to the likelihood that the most problem pathway will be found among those individuals who have experienced significant transitions earlier than most of their peers. It will be this group—those who have first sexual intercourse relatively earlier than most of their peers—that would be expected to have a greater history of difficulties prior to adolescence and who would continue to have more problems during adolescence.
In the current review, studies were organized by age of assessments of sexual behavior. This had not been done in any previous review, but is critical for an understanding of developmental issues, such as differential correlates in different age periods. The aim of using this organization was to attend to studies that predicted the earliest onset of sexual intercourse and not later onset (Early, sexual intercourse by age 15 only), first sex by up to middle adolescence (Middle, assessment of sexual intercourse that includes after age 15 but not later than age 18) or delaying onset of sexual intercourse (Late, identification of those who delayed until after age 18). Some researchers stated that attention to age was critical in their studies. For example, in some studies, an aim was to test the possibility of multiple pathways to sexual behavior (Tubman et al., 1996a, Tubman et al., 1996b, Whitbeck et al., 1999) or to study groups with different patterns of sexual behavior who were differentiated by preexisting factors or concurrent correlates (Bingham and Crockett, 1996, Crockett et al., 1996). In each of these studies, a range of measures was included that encompassed family relationships and deviant behavior. Often other potential correlates were assessed, such as biological development and quality of peer relationships, acceptance by peers or dating (Bingham and Crockett, 1996, Crockett et al., 1996, Whitbeck et al., 1999), or adolescents were grouped by their patterns of sexual behavior over a period of time and groups were compared (Tubman et al., 1996a, Tubman et al., 1996b). These studies more explicitly tested the possibility of different pathways to sexual intercourse during adolescence that depended on age of onset and correlates of sexual abstinence until after age 18.
In sum, recent longitudinal studies that assessed the age of first sexual intercourse or patterns of sexual intercourse over time were identified. Our key aim was to review studies that examined a range of factors potentially associated with adolescent early or later onset of sexual intercourse and sexual abstinence until age 18 among general community samples of U.S. adolescents. A secondary aim was to determine whether findings pointed to at least two pathways (i.e., sets of different correlates) to sexual intercourse behavior that could be linked to early versus mid-adolescence onset of sexual intercourse. We also included a review of correlates associated with sexual abstinence until the late teenage years. Longitudinal studies were included that focused on factors associated with the age, grade or timing (e.g., early, average, late) of first sexual intercourse or patterns of sexual behavior over time. In these studies, it was required that the first wave of assessment was completed when participants were younger than age 18. The definition of early sexual intercourse varied somewhat from study to study, but our organization of studies by age overcame this study variability to some extent. Yet, this review was necessarily constrained by the methodologies of included studies.
Adolescents’ biological sex1 and race/ethnicity were important factors to consider. Many researchers have recognized the importance of both of these demographic characteristics by studying only boys (e.g., Capaldi et al., 1996), girls (e.g., *Halpern, Udry, Campbell, & Suchindran, 1999), examining boys and girls separately (e.g., Meschke et al., 2000), limiting the study to racial/ethnic minority adolescents (e.g., Smith, 1997), or examining racial/ethnic groups separately (e.g., *Costa, Jessor, Donovan, & Fortenberry, 1995). Although analyses within the included studies often were conducted separately for boys and girls, rarely were gender and race/ethnicity examined as moderators of associations between sexual intercourse experience and proposed antecedents or correlates using interaction effects. This added some complexity to our review in order to highlight how correlates of adolescent sexual intercourse behavior might be identified for one or two demographic subgroups or for an ethically and racially diverse group of boys and girls, but may require additional research in order to conclude that findings apply to all demographic subgroups or significantly differ between groups. Finally, it would have been preferable to provide more information about adolescents who had sexual interests or engaged in sexual behavior with the same sex, but most studies in this systematic review did not mention gay, lesbian, or bisexual adolescents and/or sexual behaviors with the same sex.
Section snippets
Methods
We searched electronic databases to identify longitudinal studies of adolescent sexual behavior published between 1995 and 2004. Included studies examined associations between (a) adolescent age of first sexual intercourse or patterns of sexual intercourse over time and (b) individual or social factors. After meetings with content experts and a preliminary examination of a convenience sample of literature, a set of terms was selected to begin the literature search. Librarians, with involvement
Overview of the literature search and included studies
More than 1000 studies were identified in database searches (Medline, PsycInfo) and reference lists of reviews and retrieved studies. The vast majority of these studies examined sexual abuse, sexual offending, pregnancy and other factors outside the domain of this review. In addition, most were cross-sectional in design. After examination of abstracts, there were 35 longitudinal studies of U.S. adolescent sexual intercourse onset. Studies reported on 26 independent samples with at most four
Summary, discussion and conclusions
In this review of 35 recent longitudinal studies, correlates of adolescents’ sexual intercourse behaviors included physical development, problem behaviors, school-related behaviors and attitudes, sex-related attitudes, religious behavior and attitudes, mental health, and family and peer factors, including status and qualities of relationships. It was clear that age of first sexual intercourse (or patterns of sexual intercourse behavior over time) is correlated with a complicated assortment of
Conclusions
Sexual behaviors before and during adolescence emerge from a complex interplay of individual biological, and emotional, cognitive, and behavioral factors combined with the many levels of social forces that are important during particular phases of life. It is appropriate, therefore, that the studies reviewed here considered all of these elements. Given the importance of adolescent sexual development, it also was inspiring to see such a bulk of longitudinal research coming of age in the last 10
Acknowledgments
Portions of this review were funded by the Agency for Healthcare Research and Quality, Contract No. 290-97-0018, Task Order No. 7. Preventing Violence and Health Risking Social Behaviors in Adolescents and through support from the Griffith Psychological Health Research Centre. Thank you to Patty Davies at Oregon Health and Sciences University for her extremely valuable assistance with literature searching. Appreciation also is extended to Dr. Nancy Carney and Dr. Hugo de Coudray for our
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