Abstract
In view of the large burden of disease for the depressed adolescents, their families and society as a whole, studies on risk factors and mechanisms for development of a depression, as well as effect studies concerning specific treatment procedures for adolescents with depression, are definitely needed. This thesis combines several
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research questions targeting different concepts in relation to depression, namely risk factors and development of adolescent depression and the treatment of adolescent depression. This dissertation focuses on three important themes related to the development and treatment of depressive symptoms in adolescents, namely life events, cognitive emotion regulation and CBT. Life events were studied as risk factors for adolescent depression, cognitive emotion regulation was examined as a mediating mechanism between risk factors and adolescent depression and the effectiveness of CBT was investigated as a treatment for adolescent depression in clinical practice and compared to TAU. Different samples were used, including two large community samples, as well as a sample of clinically depressed adolescents. In addition different study designs were used, including a large longitudinal adult population study (NEMESIS), a longitudinal study following adolescents from 12 to 20 years of age (TRAILS) and a randomized controlled trial (RCT) studying the effectiveness of CBT (‘Doepressie’). Important results were found clarifying the relationships between depressive symptoms in adolescents and invasive life events, cognitive emotion regulation strategies and different forms of treatment. Looking into the role of life events in adolescent depression, the first study focused on the consequences of family bereavement. It was found that the devastating experience of the death of a parent during childhood was not associated with increased psychiatric diagnoses during adulthood. Most children seemed to cope well after family-bereavement and handled their emotions without developing internalizing problems. A small number of family-bereaved adolescents was found to be at risk for severe internalizing problems. Next, we identified that elevated levels of internalizing problems before bereavement, formed a risk factor for internalizing problems after bereavement. Another important risk factor that was found to increase the vulnerability in adolescents to develop depression was stressful relational life events, like conflicts between the adolescent and his/her parents or friends. In addition, in a clinical sample, it was found that depressed adolescents who experienced stressful health threats like serious illness of themselves, parents or sibling had more depressive symptoms than depressed adolescents without a health threating life event. Another focus of this thesis is on processes that contribute to the actual development of depressive symptom after the occurrence of severe life events, namely cognitive emotion regulation strategies. Maladaptive strategies, like rumination, as well as adaptive strategies, like positive reappraisal, were found to be related to elevated depressive symptoms. Maladaptive strategies were identified as mediators of depressive symptoms after stressful life events but adaptive strategies were not. Therefore it seems that stressful relational life events, put adolescents at risk for depression, and even more so when they use maladaptive cognitive emotion regulation strategies. Regarding treatment of adolescents that had a clinical diagnosis of depression, it was found that both groups that were either treated with CBT or TAU, improved significantly. CBT did not outperform TAU. However, half of the treated adolescents still experienced elevated levels of depressive symptoms by the end of the treatment. Although it was feasible to use a manualized treatment in the CBT group in routine mental health, it was also found that discontinuation of treatment in the CBT group was higher than in TAU, which resulted in new ideas that could improve CBT for depressed adolescents. This thesis covers these three themes.
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