Multimorbidity, the co-occurrence of two or more chronic conditions, is increasing in prevalence and affecting approximately a third of all adults globally. In the UK, the prevalence of individuals with four or more long-term conditions is projected to increase to 17% by 2035, compared to 9.8% in 2015. Approximately two thirds of this population will have a mental illness such as depression , which is in turn strongly associated with the incidence of a multitude of long-term conditions.
As the number of physical conditions a person increases, the odds of having a mental health disorder increase by almost double for one condition, and six times for more than five conditions. The presence of a mental health comorbidity such as depression is associated with poorer clinical outcomes and quality of life, compared to individuals with physical conditions only.
In an article published in the journal PLOS ONE, we summarised the current evidence on the association between depression and unplanned secondary healthcare use among patients with multimorbidity. To our knowledge, the literature is limited on specifically depression-related multimorbidity clusters, namely different combinations of comorbidities, or specific patient characteristics and the subsequent effect on unplanned secondary healthcare use. Therefore, this review also aimed to explore the effect of the types of comorbidities and if available, different clusters of comorbidities, and sociodemographic predictors of unplanned secondary healthcare among patients with both multimorbidity and depression.
We found that presence of depression increases the likelihood of emergency hospital admissions and readmissions in patients with multimorbidity. This association holds across a range of long-term conditions characterising multimorbidity in various countries, settings and samples. Depression also predicted increased emergency department visits in most of the studies reporting on this outcome. Moreover, the greater the severity of depression, the greater the risk of emergency hospital admissions and emergency department visits.
Patients with co-occurring depression with cancer, COPD, and asthma showed some of the greatest magnitudes of risk of unplanned secondary healthcare use. Being female, of older age and having a greater number of long-term conditions were other predictors of unplanned secondary healthcare use.