Depression and Antisocial Behaviour in Adolescents : Influence of Social Status, Shaming, and Gene-Environment Interaction

Abstract: This thesis investigated (1) social status and shaming experiences in relation to aggressive behaviour and depression, and (2) gene-environment interactions between two genetic polymorphisms related to the serotonergic system – MAOA-VNTR and 5HTTLPR – and experiences of maltreatment in relation to delinquent behaviour and depression among adolescents. The four included studies are based on questionnaire data from the Survey of Adolescent Life in Vestmanland 2006 (SALVe-2006). A total of 5396 students in 9th (15-16 years old) grade of elementary school and 2nd (17-18 years old) grade of high school comprised the target population. The students in 2nd grade of high school also provided a saliva sample for gene extraction. There were strong associations between shaming experiences and both aggressive behaviour and depression. In addition, individuals who reported many shaming experiences and had either low or high social status had increased risks of physical aggression or depression, whereas medium social status seemed to have a protective effect. Gene-environment interactions were found between experiences of maltreatment and the MAOA-VNTR in relation to delinquent behaviour. Moreover, the direction of the gene-environment interaction differed depending on sex: boys with the short (S) variant of the MAOA-VNTR, in contrast to girls with the long (LL) variant, had the highest risk of delinquency in combination with maltreatment. Gene-environment interactions were also found between experiences of maltreatment and the 5HTTLPR in relation to depression among girls. The girls that were homozygous for the S allele (SS) had the highest risk of depression in combination with maltreatment. Among boys however, no gene-environment interaction was found between the 5HTTLPR and maltreatment in relation to depression. In conclusion, it is important to consider both genetic effects, and psychosocial factors such as social status, shaming experiences, and experiences of maltreatment when investigating different aspects of health and behaviour among adolescents.