Although the exact age of onset, peak, and age of desistance varies by offense, the general pattern has been remarkably consistent over time, in different countries, and for official and self-reported data.
For example, Farrington (1983, 1986a), in a longitudinal study of a sample of boys in London (the Cambridge Longitudinal Study), found an eightfold increase in the number of different boys convicted of delinquent behavior from age 10 to age 17, followed by a decrease to a quarter of the maximum level by age 24.
Furthermore, any individual factor contributes only a small part to the increase in risk.
It is, however, widely recognized that the more risk factors a child or adolescent experiences, the higher their risk for delinquent behavior.
A longitudinal study of a representative sample from high-risk neighborhoods in Denver also found a growth in the self-reported prevalence of serious violence from age 10 through late adolescence (Kelley et al., 1997).
Females in the Denver sample exhibited a peak in serious violence in midadolescence, but prevalence continued to increase through age 19 for the boys.To fully appreciate the development of these individual characteristics and their relations to delinquency, one needs to study the development of the individual in interaction with the environment.In order to simplify presentation of the research, however, this section deals only with individual factors.These individual factors include age, gender, complications during pregnancy and delivery, impulsivity, aggressiveness, and substance use.Some factors operate before birth (prenatal) or close to, during, and shortly after birth (perinatal); some can be identified in early childhood; and other factors may not be evident until late childhood or during adolescence.Clearly, genes affect biological development, but there is no biological development without environmental input.Thus, both biology and environment influence behavior.There have been suggestions that early-onset delinquents are more likely than later-onset delinquents to be more serious and persistent offenders (e.g., Moffitt, 1993).There is evidence, however, that predictors associated with onset do not predict persistence particularly well (Farrington and Hawkins, 1991).Research over the past few decades on normal child development and on development of delinquent behavior has shown that individual, social, and community conditions as well as their interactions influence behavior.There is general agreement that behavior, including antisocial and delinquent behavior, is the result of a complex interplay of individual biological and genetic factors and environmental factors, starting during fetal development and continuing throughout life (Bock and Goode, 1996).