Cause-Specific Mortality and Physical Fitness in Mental Disorders - Epidemiological and Internventional Studies

Abstract

Mental illnesses are common and constitute a substantial health-related and financial burden on both the individual and society. Mental disorders in general have increased risk of somatic morbidity. An early age of onset is commonly seen in anxiety disorders and the prevalence of these disorders has increased in youth in recent years. The overall aim of this thesis was to study mental disorders and the importance of cardiovascular fitness regarding both prevention and intervention and the association with cause-specific mortality. Studies I and II use data from several national registers to prospectively analyse if cardiovascular fitness in late adolescence is associated with future risk for mental disorder and how familial factors might impact the relationship. Furthermore, the aim in Study II was to estimate risk associated with specific causes of natural death in individuals with non-psychotic mental (NPM) disorders. Studies III-V emanate from a randomized, controlled clinical trial (RCT) set in primary care designed to evaluate the effects of an exercise intervention in persons with anxiety disorders. Patients were randomly assigned to either a) low-intensity training b) moderate to high intensity training or c) a control group, with three assessment points (baseline, post-intervention and one-year follow-up). Study I and II were nationwide cohort studies of young men born between 1950 and 1987 who enlisted for military service between 1968 and 2005. Data was extracted from the Swedish Military Service Conscription Register. By linking conscription data to the Swedish National Hospital and Cause of Death Register we identified 1.1 million male conscripts in Study I and 1.8 million in Study II, with a follow-up of up to 46 years. We showed in Study I that lower fitness in late adolescent males was associated with increased risk of schizophrenia and other psychotic disorders as well as anxiety and stress-related disorders in adulthood. Relationships persisted in models also adjusting for familial factors. In Study II we showed that young men diagnosed with NPM disorders had a long-term increased mortality risk, in particular due to gastrointestinal and infectious conditions with up to four-fold increased mortality risk for depressive and neurotic/adjustment disorders, personality disorders and alcohol-related/substance use disorders. Study III is the study protocol describing our 12-week exercise intervention program for patients diagnosed with anxiety disorders within primary care. In Study IV, cross-sectional data at baseline from this RCT showed that severity of anxiety was associated with executive functions related to working memory but not with fluid intelligence. In Study V we could show that the 12-week exercise program improved symptoms of anxiety in patients with anxiety disorders in primary care, in both low and moderate- to high intensity exercise groups. No differences in effect sizes were found between intensity exercise groups. In conclusion our findings show that low cardiovascular fitness in adolescence increases the risk for mental disorders later in life and that men with NPM disorders have an increased mortality risk. We could also show that a 12-week group exercise program proved to be an effective treatment for individuals with anxiety disorders in primary care. Further, we found an association between anxiety severity and working memory that need more elucidation. These findings, taken together with the knowledge that mental illness is increasing highlights the importance of preventive actions to improve cardiovascular fitness. Implementation of exercise in the treatment of anxiety disorders should be prioritized.