Various researchers categorize risk factors in different ways. For the purposes of this article, risk factors fall under three broad categories: individual, social, and community. Each of these categories includes several subcategories (e.g., family- and peer-related risk factors are grouped under the social category). Because an exhaustive review of all known risk factors linked to delinquency is beyond the scope of this article,³ the following summarizes the major risk factors associated with juvenile delinquency and violence.

Prenatal and perinatal factors. Several studies have linked prenatal and perinatal complications with later delinquent or criminal behavior (Kandel et al., 1989; Kandel and Mednick, 1991; Raine, Brennan, and Mednick, 1994). Prenatal and perinatal complications can lead to a range of health problems that negatively influence development (McCord, Widom, and Crowell, 2001). In a prospective study of youth at high risk for delinquency, Kandel and Mednick (1991) found that 80 percent of violent offenders rated high in delivery complications compared with 47 percent of nonoffenders.

However, some of the evidence regarding the association between pregnancy and delivery complications and delinquency has been conflicting (Hawkins et al., 1998). For example, neither Denno's (1990) study of Philadelphia youth nor Farrington's (1997) Cambridge study found a connection between pregnancy and delivery complications and violence. Mednick and Kandel (1988) linked pregnancy and delivery complications to violent behavior, but not to nonviolent criminal behavior. In addition, some studies have shown that children whose mothers smoked cigarettes frequently during pregnancy were more likely to display conduct disorders and other problem behaviors (Fergusson, Horwood, and Lynskey, 1993; Wakschlag et al., 1997). Although the results are inconsistent, the available data illustrate the need to study further the relationship between prenatal care, delivery complications, and the resulting health problems and juvenile delinquency (Hawkins et al., 1998).

Psychological, behavioral, and mental characteristics. Several individual-specific characteristics are linked to delinquency. Tremblay and LeMarquand (2001:141) remarked that "the best social behavior characteristic to predict delinquent behavior before age 13 appears to be aggression." In addition, Hawkins and colleagues (1998:113) reviewed several studies and reported "a positive relationship between hyperactivity, concentration or attention problems, impulsivity and risk taking and later violent behavior." Low verbal IQ and delayed language development have both been linked to delinquency; these links remain even after controlling for race and class (Moffitt, Lynam, and Silva, 1994; Seguin et al., 1995). Similarly, problems at school can lead to delinquency. Herrenkohl and colleagues (2001:223) noted that "children with low academic performance, low commitment to school, and low educational aspirations during the elementary and middle school grades are at higher risk for child delinquency than are other children."

Family structure. Family characteristics such as poor parenting skills, family size, home discord, child maltreatment, and antisocial parents are risk factors linked to juvenile delinquency (Derzon and Lipsey, 2000; Wasserman and Seracini, 2001). McCord's (1979) study of 250 boys found that among boys at age 10, the strongest predictors of later convictions for violent offenses (up to age 45) were poor parental supervision, parental conflict, and parental aggression, including harsh, punitive discipline. Some research has linked being raised in a single-parent family with increased delinquency (McCord, Widom, and Crowell, 2001); however, when researchers control for socioeconomic conditions, these differences are minimized (Austin, 1978; Crockett, Eggebeen, and Hawkins, 1993). Some research has shown that children from families with four or more children have an increased chance of offending (Wasserman and Seracini, 2001; West and Farrington, 1973).

Peer influences. Several studies have found a consistent relationship between involvement in a delinquent peer group and delinquent behavior. Lipsey and Derzon (1998) noted that for youth ages 12–14, a key predictor variable for delinquency is the presence of antisocial peers. According to McCord and colleagues (2001:80), "Factors such as peer delinquent behavior, peer approval of delinquent behavior, attachment or allegiance to peers, time spent with peers, and peer pressure for deviance have all been associated with adolescent antisocial behavior." Conversely, Elliot (1994) reported that spending time with peers who disapprove of delinquent behavior may curb later violence. The influence of peers and their acceptance of delinquent behavior is significant, and this relationship is magnified when youth have little interaction with their parents (Steinberg, 1987).

Farrington (2000:5) noted that "only in the 1990's have the longitudinal researchers begun to pay sufficient attention to neighborhood and community factors, and there is still a great need for them to investigate immediate situational influences on offending." As described below, the environment in which youth are reared can influence the likelihood of delinquency.

School policies. The National Research Council and the Institute of Medicine reviewed the impact of school policies concerning grade retention,⁴ suspension and expulsion, and school tracking of juvenile delinquency. These organizations reported that such policies, which disproportionately affect minorities, have negative consequences for at-risk youth (McCord, Widom, and Crowell, 2001). For example, suspension and expulsion do not appear to reduce undesirable behavior, and both are linked to increased delinquent behavior. In addition, Heal's (1978) cross-sectional study of primary and secondary schools in England found that large schools with formal and severe punishment structures in place had more incidents of students misbehaving.

Neighborhood. Existing research points to a powerful connection between residing in an adverse environment and participating in criminal acts (McCord, Widom, and Crowell, 2001). Sociological theories of deviance hypothesize that "disorganized neighborhoods have weak social control networks; that weak social control, resulting from isolation among residents and high residential turnover, allows criminal activity to go unmonitored" (Herrenkohl et al., 2001:221). Although researchers debate the interaction between environmental and personal factors, most agree that "living in a neighborhood where there are high levels of poverty and crime increases the risk of involvement in serious crime for all children growing up there" (McCord, Widom, and Crowell, 2001:89).