Exploring the Comorbidity Between Mental Disorders and General Medical Conditions

Mental disorders have been shown to be associated with a number of general medical conditions (also referred to as somatic or physical conditions). The investigators aim to undertake a comprehensive study of comorbidity among those with treated mental disorders, by using high-quality Danish registers to provide age- and sex-specific pairwise estimates between the ten groups of mental disorders and nine groups of general medical conditions.
The investigators will examine the association between all 90 possible pairs of prior mental disorders and later GMC categories using the Danish national registers. Depending on whether individuals are diagnosed with a specific mental disorder, the investigators will estimate the risk of receiving a later diagnosis within a specific GMC category, between the start of follow-up (January 1, 2000) or at the earliest age at which a person might develop the mental disorder, whichever comes later. Follow-up will be terminated at onset of the GMC, death, emigration from Denmark, or December 31, 2016, whichever came first. Additionally for dyslipidemia, follow-up will be ended if a diagnosis of ischemic heart disease was received. A "wash-out" period will be employed in the five years before follow-up started (1995-1999), to identify and exclude prevalent cases from the analysis. Individuals with the GMC of interest before the observation period will be considered prevalent cases and excluded from the analyses (i.e. prevalent cases were "washed-out"). When estimating the risk of a specific GMC, the investigators will consider all individuals to be exposed or unexposed to the each mental disorder depending on whether a diagnosis is received before the end of follow-up. Persons will be considered unexposed to a mental disorder until the date of the first diagnosis, and exposed thereafter.