Sickness absence : subsequent psychiatric morbidity and suicidal behaviour

Abstract: Background: Sickness absence is a frequent recommendation in Swedish health care. Yet, research on future health outcomes of being sickness absent is sparse. Mental disorders are one of the most common diagnostic groups for sickness absence. Knowledge on psychiatric morbidity and suicidal behaviour following sickness absence is therefore of special interest. Exploring this should be done by using different sick-leave measures and by exploring differences over time, for instance, in relation to changes of social insurance regulations. The aim of this thesis was to investigate different aspects of the associations between sickness absence and subsequent morbidity, suicide attempt, and suicide. Methods: Four population-based longitudinal cohort studies were conducted, using nationwide Swedish register data. All individuals aged 16-64 years who lived in Sweden as on 31 December 2004 (n=4 923 404), and all individuals aged 20-64 years who lived in Sweden as on 31 December 2005 or 2008 (n=4 477 678; n=4 500 400), respectively, and who were not on old-age or disability pension were followed up for six years in Study I and for two years in Study IV. In Study II, all such individuals aged 16-64 years who lived in Sweden as on 31 December 2004 and had in- or specialised outpatient care due to depressive disorders in 2005 were included (n=21 096). In Study III, 4209 individuals aged 22-65 years who committed suicide in 2007-2010 were included. In all the studies, information on socio- demographics, health care, medication, sickness absence, disability pension, and death was linked at individual level from registers held by the Social Insurance Agency, the National Board of Health and Welfare, and Statistics Sweden. Cox regression analyses were performed to estimate associations between sickness absence and inpatient care and suicidal behaviour (Study I, II, and IV). A group-based trajectory method was applied to identify sickness absence/disability pension trajectories in the five years before the suicide (Study III). Results: Individuals who had been sickness absent, measured as incidence all-cause and diagnosis-specific sickness absence and sick-leave duration, showed a higher risk of subsequent suicide attempt and suicide compared to those without sickness absence (Study I and IV). Higher risks of suicidal behaviour associated with all-cause and diagnoses-specific sick-leave incidence and sick-leave duration were also observed among patients with depressive disorders (Study II). Among patients with depressive disorders and not on disability pension, those who had one or more incident sick-leave spells or had been full-time sickness absent had higher hazard ratios of suicide attempt in the following five years than those with no sickness absence (Study II). Individuals on sickness absence due to common mental or musculoskeletal diagnoses or with long-term sickness absence (>180 days) in 2009 had higher hazard ratios of subsequent inpatient care due to somatic disorders compared to those on such sickness absence in 2006 (i.e. before the regulatory change in 2008) (Study IV). Among those who committed suicide, five different previous sickness absence/disability pension trajectories were identified (Study III). Almost half of the suicide victims had had constantly low levels of sickness absence/disability pension, while 30% had constantly high such levels in the five years before the suicide. The trajectories were characterised by differences in socio-demographic and health care factors. Conclusions: Sickness absence was a risk marker for suicidal behaviour, irrespective of sick-leave diagnoses, both for women and men in the general population and for patients with depressive disorders. In addition, incident mental or somatic sickness absence and long- term sickness absence after the regulatory change in 2008 might be associated with a higher medical severity than such sickness absence before the change. More knowledge is warranted on such associations as bases for preventive actions.