Lescents may focus on an individual’s relationships and social status as an effective target for causing the most harm (Buhrmester, 1996; Zimmer-Gembeck, Geiger Crick, 2005). However, the majority of previous studies that have investigated Ro4402257 msds trajectories of social aggression have been limited to early through late childhood. One longitudinal study examining indirect aggression from ages 4 ?8 found that although the majority of participants (67.9 ) followed a stably low trajectory, 32.1 of children followed a steadily increasing trajectory (Cot? Vaillancourt, Barker, Nagin Tremblay, 2007). More recently, a longitudinal study assessed children between 4 and 11 years old identified four indirect aggression trajectories. Participants on the non-aggressive and low aggression trajectories remained stable; the moderate- and high-trajectories of indirect aggression both followedAggress Behav. Author manuscript; available in PMC 2015 September 01.Ehrenreich et al.Pagedevelopmental courses that increased until approximately age 7 and then remained generally stable through the final assessment wave when participants were 11 years old (although boys on the high trajectory remained slightly more stable across time than girls; Pagani, Japel, Vaillancourt Tremblay, 2010). Both of these studies used parent-reports of aggression. The few studies that have examined the developmental course of social aggression during middle-childhood through adolescence have found somewhat conflicting results. An examination of data from the NICHD Study of Early Child Care and Youth Development (SECCYD) found that from ages 8 ?11, relational aggression as rated by teachers and parents remained stable for girls but declined slightly for boys (Spieker at al., 2012). In a study of earlier waves of the same sample presented in this study, Underwood, Beron and Rosen, (2009) examined teacher-reports of social aggression and identified two trajectories: one stably low and the other decreasing steadily from age 9 through 13. In a study of selfreports of aggression from ages 10 ?15 the National Longitudinal Survey of Children and Youth in Canada (NLSCYC), three developmental trajectories for indirect aggression emerged: low-declining, moderate-declining, and high (Cleverly, Szatmari, Vaillancourt, Boyle, Lipman, 2012). In a study with rural middle and high-school students, self-report data indicated that both boys and girls followed a curvilinear trajectory that showed increases in socially aggressive behavior from ages 11 ?14 years old followed by a rapid decline through age 18 (Karriker-Jaffe et al., 2008).NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptDevelopmental Course of ML390 cancer Physical AggressionDuring late childhood through early adolescence, most children engage in physical aggression infrequently, or do not engage in physical aggression at all (Broidy et al., 2003; Dodge et al., 2006; Huesmann et al., 2009). Despite this, some children continue to engage in moderate or high levels of aggression through late childhood and into adolescence (Brame et al., 2001; Dodge et al., 2006; Huesmann et al., 2009). Even for those children who do continue to engage in physical aggression during middle and late adolescence, the majority follow desisting trajectories (Brame et al., 2001; Nagin Tremblay, 1999; Underwood et al., 2009). Boys are more likely to engage in physical aggression in childhood and adolescence (Archer, 2004; Card, Stucky, Sawalani Li.Lescents may focus on an individual’s relationships and social status as an effective target for causing the most harm (Buhrmester, 1996; Zimmer-Gembeck, Geiger Crick, 2005). However, the majority of previous studies that have investigated trajectories of social aggression have been limited to early through late childhood. One longitudinal study examining indirect aggression from ages 4 ?8 found that although the majority of participants (67.9 ) followed a stably low trajectory, 32.1 of children followed a steadily increasing trajectory (Cot? Vaillancourt, Barker, Nagin Tremblay, 2007). More recently, a longitudinal study assessed children between 4 and 11 years old identified four indirect aggression trajectories. Participants on the non-aggressive and low aggression trajectories remained stable; the moderate- and high-trajectories of indirect aggression both followedAggress Behav. Author manuscript; available in PMC 2015 September 01.Ehrenreich et al.Pagedevelopmental courses that increased until approximately age 7 and then remained generally stable through the final assessment wave when participants were 11 years old (although boys on the high trajectory remained slightly more stable across time than girls; Pagani, Japel, Vaillancourt Tremblay, 2010). Both of these studies used parent-reports of aggression. The few studies that have examined the developmental course of social aggression during middle-childhood through adolescence have found somewhat conflicting results. An examination of data from the NICHD Study of Early Child Care and Youth Development (SECCYD) found that from ages 8 ?11, relational aggression as rated by teachers and parents remained stable for girls but declined slightly for boys (Spieker at al., 2012). In a study of earlier waves of the same sample presented in this study, Underwood, Beron and Rosen, (2009) examined teacher-reports of social aggression and identified two trajectories: one stably low and the other decreasing steadily from age 9 through 13. In a study of selfreports of aggression from ages 10 ?15 the National Longitudinal Survey of Children and Youth in Canada (NLSCYC), three developmental trajectories for indirect aggression emerged: low-declining, moderate-declining, and high (Cleverly, Szatmari, Vaillancourt, Boyle, Lipman, 2012). In a study with rural middle and high-school students, self-report data indicated that both boys and girls followed a curvilinear trajectory that showed increases in socially aggressive behavior from ages 11 ?14 years old followed by a rapid decline through age 18 (Karriker-Jaffe et al., 2008).NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptDevelopmental Course of Physical AggressionDuring late childhood through early adolescence, most children engage in physical aggression infrequently, or do not engage in physical aggression at all (Broidy et al., 2003; Dodge et al., 2006; Huesmann et al., 2009). Despite this, some children continue to engage in moderate or high levels of aggression through late childhood and into adolescence (Brame et al., 2001; Dodge et al., 2006; Huesmann et al., 2009). Even for those children who do continue to engage in physical aggression during middle and late adolescence, the majority follow desisting trajectories (Brame et al., 2001; Nagin Tremblay, 1999; Underwood et al., 2009). Boys are more likely to engage in physical aggression in childhood and adolescence (Archer, 2004; Card, Stucky, Sawalani Li.