Anxiety and depression in adolescent females : Autonomic regulation and differentiation

The prevalence of anxiety and depression is on the increase in adolescent girls, as estimated by self-assessed symptom reports. There is a need for implementation of validated instruments to identify those in need of treatment. The concept of autonomic self-regulation may help us to elucidate possible pathophysiological pathways of anxiety disorders and depression. Heart rate variability (HRV) provides a tool to assess the descending vagal inhibitory tone, i.e. the capacity of autonomic self-regulation. This perspective gives a framework for evaluating practices of allostatic competence as possible methods for preventing and treating of anxiety disorders and depression in adolescent girls. The present work is intended to create a platform for future studies aimed in this direction. Study I demonstrated that autonomic regulation measured by HRV is decreased in adolescent female psychiatric patients with anxiety disorders and/or major depressive disorder (MDD) compared to healthy controls, which was partly explained by selective serotonin reuptake inhibitor (SSRI) medication, but not by lack of physical activity or cardiovascular risk factors. It thus seemed as if depressive and anxious symptoms contributed to impaired vagal inhibitory control in adolescent girls. Study II investigated whether lifestyle factors, that are accessible for intervention, are related to HRV in healthy adolescents and conclude that physical activity, but not eating habits, sleep pattern or smoking, was related to HRV, without contribution from gender, systolic blood pressure, plasma-glucose, body mass index or socio-demographic factors. The data provides a basis for future studies of interventional design. Study III showed that the emotional subscale of Strengths and Difficulties Questionnaire (SDQ-em) and the putative salutogenic scale of Sense of Coherence (SOC) were equivalent or even superior to the specialized self-assessment scales for anxiety and depression in their ability to differentiate cases of anxiety disorders and major depressive disorder from non-cases in adolescent girls. The study thus supports the accuracy of SDQ-em as a screening instrument for anxiety and depression and as a tool to discriminate between caseness and non-caseness of emotional disorders in adolescent girls. Study IV was an in depth investigation of the construct of Sense of Coherence (SOC) applied in adolescent girls, showing that it lacks a unique dimensionality as a salutogenic construct, but constitutes a sensitive inverse measure of persistent depressive and generalized anxiety problems similar to diagnoses such as major depressive disorder (MDD), dysthymic disorder (DD), generalized anxiety disorder (GAD) or generalized social anxiety disorder (SAD) according to DSM-IV. It was also demonstrated that a low SOC score was correlated to a decrease in HRV