Anna-Karin Andershed, Örebro University

The original purpose of the project  was to investigate the develoment and adjustment of aggressive girls during adolescence. Our focus was key risk- and protective factors, and developmental trajectories for aggressive girls. The main research questions concerned whether aggressive girls' problems are different and more hidden than aggressive boys' problems; whether the pattern of consequences of girls' aggression changes when a broader range of types of aggression is considered, and; whether we need to consider more hidden negative consequences of aggression also for boys. The purpose has changed insomuch that the emphasis on girls' unique patterns of expression and consequences of aggression has shifted toward an emphasis on similarities in patterns of expression and consequences of aggression between girls and boys. The most pivotal manuscripts for the project refer to these lines of reasoning, from different perspectives (Andershed, 2008; Andershed & Magnusson, in press).

During the course of the project we have seen that the clear gender differences in expression of aggression that has been reported in the international research literature, is not to be found among the Swedish adolescents participating in our studies. In two independent samples, we have been able to show that boys are more physically, overtly aggressive than girls, but that girls are not more relationally, socially aggressive than boys. Rather, it seems as if boys are more aggressive than girls regardless of what type of aggression that is under study, even though gender differences in relational, social aggression are not statistically significant.

We have also been able to clearly show that the consequences of girls' and boys' aggression are very similar. Concerning differences between low- and high-aggressive boys and low- and high-aggressive girls, respectively, in areas such as relationships with others, and substance use, the same patterns of negative consequences emerge for high-aggressive adolescents, regardless of gender. More limited differences in patterns of negative consequences are being observed for depression and antisocial behavior, where high-aggressive girls seem to be more troubled by depressive symptoms than low-aggressive girls, while high-aggressive boys seem to express more antisocial behavior than low-aggressive boys. This does not mean that high-aggressive girls do not have problems with antisocial behavior, or that high-aggressive boys do not have problems with depressive symptoms - rather, the differences between genders in patterns of consequences are slightly larger than when it comes to other consequences.

From a more narrow perspective and the research area of aggression, we have been able to show that it is possible to relatively clearly separate so called proactive (instrumental) and reactive (hostile) aggression when it comes to overt expressions of aggression, such as physical and verbal aggression. The same differentiation is not possible when it comes to relational, social aggression. Again, the patterns of results are very similar for boys and girls. Also, it seems as if different types of aggression not necessarily are related to different consequences.

Further studies and preliminary analyses have also shown that:
* the association between a negative parent-child relationship and antisocial behavior is partly explained by the child's aggression (behavior-genetic study)
* aggressive girls do not self-harm more than other girls
* the relation between aggression and social adjustment is related to pubertal maturation, where early pubertal maturation seems to accelerate the aggressive girls' risk for negative social adjustment, while late pubertal maturation seems to be protective for the aggressive girls.

The results this project has generated has pointed out some areas that stand out as important to proceed with, of which some we have taken further:
* the possibility to generalize research results concerning aggression to antisocial and normbreaking behavior in general
* early identification. How early is it possible to observe different types of aggression? How early is it possible to utilize aggression as a predictor of future problems?
* self-harm and aggression. Professsionals working with aggressive adolescents in clinical practice argue that self-injurious behaviors are more common among the girls than among the boys that they encounter. It is an empirical question whether self-harm is related to aggression.
* a differentiation between different developmental trajectories to girls' and women's problems. There is research indicating that aggression as well as internalizing problems can lead to similar problems. This is being investigated (see Aggression and depression: Two pathways to similar problems.).

The results from this project has been reported in scientific papers, book chapters, and conference presentations. My involvement in these research questions has also facilitated my participation as editor of two edited books concerning girls' and women's problems. The results have been reported in the media, and the project has resulted in a number of undergraduate theses in psychology. See Publication list. I have also been invited to an international network for collaboration on aggression from a gender perspective, funded by CIHR International Opportunities Program - Development/Planning (Understanding aggression and violence in adolescent girls and boys: A cross-cultural examination in developmental pathways, social, physical and mental health outcomes; Marlene M. Moretti (PI), Candice Odgers, Debra J. Pepler, & Anna-Karin Andershed.)