Physical-mental health comorbidity: A population-based cross-sectional study.

Background: Multimorbidity is associated with physical-mental health comorbidity (PMHC). However, the scope of overlap between physical and mental conditions, associated factors, as well as types of mental illness involved are not well described in Eastern Europe. This study aims to assess the PMHC burden in the Estonian population.
Methods: In this population-based cross-sectional study we obtained health claims data for 55 chronic conditions from the Estonian Health Insurance Fund (EHIF) database, which captures data for all publicly insured individuals (n = 1 240 927 or 94.1% of the total population as of 31 December 2017). We assessed the period-prevalence (3 years) of chronic physical and mental health disorders, as well as associations between them, by age and sex.
Results: Half of the individuals (49.1% (95% CI 49.0-49.3)) had one or more chronic conditions. Mental health disorders (MHD) were present in 8.1% (8.1-8.2) of individuals, being higher among older age groups, women, and individuals with a higher number of physical conditions. PMHC was present in 6.2% (6.1-6.2) of the study population, and 13.1% (13.0-13.2) of the subjects with any chronic physical disorder also presented with at least one MHD. Dominating MHDs among PMHC patients were anxiety and depression. The prevalence of MHD was positively correlated with the number of physical disorders. We observed variation in the type of MHD as the number of physical comorbidities increased. The prevalence of anxiety, depression, and mental and behavioral disorders due to the misuse of alcohol and other psychoactive substances increased as physical comorbidities increased, but the prevalence of schizophrenia and dementia decreased with each additional physical disease. After adjusting for age and sex, this negative association changed the sign to a positive association in the case of dementia and mental and behavioral disorders due to psychoactive substance misuse.
Conclusions: The burden of physical-mental comorbidity in the Estonian population is relatively high. Further research is required to identify clusters of overlapping physical and mental disorders as well as the interactions between these conditions. Public health interventions may include structural changes to health care delivery, such as an increased emphasis on integrated care models that reduce barriers to mental health care.
Competing Interests: The authors declare that they have no competing interests.