Twin Pair Studies Interlinking Genetics, Environment, and Anxiety Domains with Anger

The co-occurrence of anger or aggressive behaviors and anxiety, especially in children and adolescents, is an extremely recurrent phenomenon, widely documented in all diagnostic manuals. The comorbidity bond between these disorders seems to be one of the main reasons why the treatment of their symptoms is often challenging. In the present chapter, multivariate twin studies on the etiological factors at the basis of this co-occurrence are reviewed. In the first part, basic principles of behavior genetics with a specific focus on the different methodological variants of twin studies designs are introduced. Afterward, an analysis of the results of those works aimed at unraveling the genetic and environmental contribution to the co-occurrence between anger, aggression, irritability, and anxiety is proposed. The final part of the chapter provides a consideration on the benefits that the identification of these etiological factors can have, especially in relation to the treatment of these disorders.