Most literature on adolescent consequences of risky behaviors focuses on risky behaviors as outcomes, with some studies examining other outcomes such as educational attainment and employment. Risky behaviors beget other risky behaviors. The fact that adolescent risky behaviors often co-occur makes engaging in any one risky behavior a risk factor for engaging in another. Lindberg, Boggess, and Williams' (1999) results somewhat support the interconnectedness of adolescent risk behaviors. These researchers studied the co-occurrence of adolescent risk behaviors using data from 7th to 12th graders in the 1995 Add Health survey. They found that 28 percent of 7th to 12th graders indicated engaging in two or more risk behaviors, including regular or recent substance use, fighting, carrying a weapon, suicidal thoughts and ideation, and unprotected sexual intercourse. More than one-quarter of students, though, only participated in a single risky behavior. For all of the risk behaviors they examined, except for one, at least three-quarters of the students engaging in it were also involved in another risk behavior.
In a study using two large national data sets, the Youth Risk Behavior Survey (YRBS) and Add Health, the Center on Addiction and Substance Abuse (CASA 1999) found that teenagers who consume alcohol or take illicit drugs are more likely to engage in sex, to do so at a younger age, and to have several partners. For adolescents who are 14 and younger, consuming alcohol or using drugs doubles and quadruples, respectively, the likelihood that sexual intercourse has ever been experienced compared to adolescents who have never used these substances. Moore, et al (1995) reported that early onset of alcohol, tobacco, and other drugs; school problems; delinquency; and physical aggression are significantly associated with early onset of sexual behavior. Alcohol use in adolescence has also been found to be related to more frequent sexual activity and less frequent use of condoms (Cooper, Peirce, and Huselid, 1994).
Another example of adolescent risky behaviors occurring in conjunction with each other comes from research using the 1998 NHSDA (OAS, 2000). In this report, about 40 percent of alcohol users age 12 to 17 were also current illicit drug users. This percentage increased to 58 percent of binge drinkers and 69 percent of heavy drinkers who had used an illicit drug in the past month. Past-year criminal activity also co-occurred with substance use. Adolescents who had consumed alcohol in the previous month were more likely than those who had not to also have engaged in criminal activity in the past year. In general, the heavier the alcohol use, the greater the probability of criminality. Adolescents who drank in a heavy manner were more likely than lighter drinkers to be involved in a variety of delinquent acts and to show aggressive behavior, such as physically attacking people or destroying property.
Johnson, Arria, et al (1995) identified a connection in preadolescence between early, unsanctioned alcohol use (without permission from their parents) and higher levels of conduct problems. Earlier alcohol use was also associated with accelerated growth of conduct problem behaviors during the transition to early adolescence. The literature on adolescent conduct problems and substance use supports the notion of an "externalizing (behavioral) path" leading to substance use, particularly for males (Hussong, Curran, and Chassin, 1998). Windle (1990) found that even when holding early substance use constant, early adolescent delinquency predicted later substance use.
Each adolescent risk behavior also has some very specific consequences. We present these consequences, categorized under the relevant adolescent risk behavior.
Risky sexual behavior
The logical concerns arising from adolescent sexual behavior are pregnancy, parenthood, infection with a sexually transmitted disease, and exposure to the human immunodeficiency virus (HIV). Individuals who begin having sex at earlier ages are exposed to risk for a greater length of time, are less likely to use contraception, have more sexual partners, and are involved in high risk sexual behavior, such as substance use before intercourse (Moore, et al., 1995). Moore, et al also reported that another possible concern about early sexual behavior is that first sexual experiences are often coercive. An astonishing majority of first sexual experiences that occurred before age 15 among females were not voluntary. Coercion is damaging in itself, but it is also associated with improper or no use of contraception.
Conduct problems in childhood and early adolescence have been found to be associated with substance use problems later in adolescence (Lynskey and Fergusson, 1995; Windle, 1990). Results from Bergmark and Andersson's (1999) longitudinal study that followed Swedish participants from childhood to adulthood revealed that the earlier the conduct problems for boys, the more frequent the occurrence of adolescent drunkenness. Other research has found a significant relationship between delinquency and school attachment. Liska and Reed (1985) used data from the first two waves of the Youth in Transition study to examine this issue. They found that attachment to school has no influence on adolescent violence, but the reverse of this relationship, that violence decreases school attachment, was significant.
A possible consequence for adolescents who engage in substance use behavior is that this risky behavior can lead to increased, problematic use of a given substance. Early initiation of alcohol use was predictive of later adolescent problem drinking (Fergusson, Lynskey, and Horwood, 1994; Hawkins, et al, 1997; Pedersen and Skrondal, 1998). Kosterman, et al. (2000) found a connection between age of initiation of alcohol use and alcohol misuse later in adolescence. Hawkins, et al. (1997) also found that the younger the age of alcohol initiation, the greater the level of alcohol-related problems in late adolescence (see also Gruber, et al 1996). In this study, age of initiation served as a mediator of effects of ethnicity, parents' alcohol consumption, proactive parenting, school bonding, friends' alcohol initiation, and perceptions of alcohol's harmfulness on alcohol misuse in late adolescence (Hawkins, et al., 1997). In other words, when age of initiation was entered into the model predicting adolescent alcohol misuse, these formerly significant variables no longer showed any effect on the outcome. Fergusson, Lynskey, and Horwood (1997) reported that onset of marijuana use before age 15 had a relationship with later marijuana use.
There is also legitimate concern that adolescent substance use can lead to use of "harder" substances. Yamaguchi and Kandel (1984) provided evidence for a gateway model of drug use. In their model, use of softer substances, such as alcohol and cigarettes, open the gates to the use of marijuana, which in turn makes the use of other illicit drugs more likely.
Earlier adolescent marijuana use has been found to increase the risk of a variety of negative outcomes in later adolescence. Early marijuana use is predictive of not graduating from high school; delinquency; mental health problems; having multiple sex partners; inconsistent condom use; perception of drugs as not harmful; having problems with alcohol, tobacco, and other drugs; and having deviant friends (Brook, Balka, and Whiteman, 1999; Fergusson and Horwood, 1997). Fergusson and Horwood (1997) examined the issue of marijuana use and adjustment in adolescence with data from a longitudinal study in which a sample of New Zealand children were surveyed regularly from birth to age 18 years old. Even after controlling for childhood, family, and other potential risk factors, those respondents who indicated early marijuana use, especially more frequent use, were more likely to have a marijuana use disorder, use other substances, be unemployed, engage in delinquent acts, and drop out of school early by age 18.