Evidence Alert: Risk of Psychiatric Co-Morbidity

Evidence Alert: Risk of Psychiatric Co-Morbidity

Diagnosed psychiatric conditions are common, with an estimated 20% of Australians aged 16-85 years old experiencing a mental health disorder in a given year. They are also associated with high levels of disability (the WHO now lists depression as the leading cause of disability in the world).

Assessing the risk associated with diagnosis of a past psychiatric condition in an individual is challenging but important. There are lots of factors to consider (personal, diagnosis related, and environmental factors). Some of the diagnosis related factors include: what the diagnosis was; its severity; treatment; risk of recurrence; and risk of psychiatric co-morbidity (or the development or later diagnosis of another psychiatric condition).

In January this year there was a fascinating and important study [1] published in JAMA Psychiatry, one that should be read by anyone in life underwriting or claims.

Importantly, the study found that if a patient was diagnosed with any prior mental health disorder, they were seemingly at risk for development of any other class of mental health disorder at a later stage. This risk was highest within the first year following the initial diagnosis (probably representing initial diagnostic uncertainty), but then remained elevated for the next 15 years.

The study also adds evidence to the shared factors model of mental health disorder development or pathogenesis. This model that proposes there are shared genetic and environmental risk factors underlying all mental health disorders.

The strengths of the study were its size (5.9 million Danish people) and the duration of follow up (up to 17 years of follow up for individuals, and 83 million years of follow up in aggregate). The researchers also grouped diagnoses by their ICD10 codes and looked at diagnostic clusters such as substance use disorders, eating disorders, mood disorders and personality disorders. To me, one of the major strengths of the study was that the researchers made their findings available to the public, and used an amazing data visualisation tool to let the public explore the methodology, the results, and conclusions.

The website to explore the study and findings is here:


It is worth time to work through the site, as it explains several core features of the study and their results really well. You can easily select a prior mental health disorder and see how the risk for other groups of mental health disorder changes over time.

A few considerations to note when interpreting the study: the subjects in the study were recruited from hospitals (either in-patients, out-patients, or from the emergency room). Many studies on mental health disorders recruit patients from hospitals, and it this probably means the subjects studied have a more severe mental health disorder than most. The researcher indicate they intend to consider people assessed and treated by their GPs in further work, the information from this study will be very interesting.

  1. Plana-Ripoll, O., et al., Exploring Comorbidity Within Mental Disorders Among a Danish National Population. JAMA Psychiatry, 2019.

 Dr Matthew Paul is an occupational physician with 20 years of clinical experience, and an interest in occupational disability and risk assessment. Working as CMO for Munich Re.