Link between autoimmune disorders and psychosis confirmed

Researchers at King’s College London have found the strongest evidence yet of a link between autoimmune disorders and psychotic disorders such as schizophrenia. The study, published today in Biological Psychiatry combined the results of 30 scientific publications, including data from over 25 million individuals worldwide.

The researchers found that psychosis was more common among people with a range of conditions, such as pernicious anaemia, psoriasis and coeliac disease, but less common among people with rheumatoid arthritis and ankylosing spondylitis. The results raise questions about the biological mechanisms behind this complex relationship.

Lead researcher Dr Alexis Cullen from the Institute of Psychiatry, Psychology & Neuroscience says: ‘Our study shows that overall, people with any autoimmune disorder are around 40% more likely to develop psychotic disorders such as schizophrenia. The finding that psychosis is associated with non-neurological autoimmune disorders, which are not known to directly target the brain, is particularly important.’

The idea that there is a relationship between autoimmune disorders and psychosis is not new; it was first observed in the 1950s that rheumatoid arthritis was less common among individuals with psychosis than would be expected in the general population. However, later studies found that individuals with other autoimmune disorders were more likely to have psychosis. These conflicting findings were puzzling and indicated the need for a more robust review of the evidence to date.

After pooling data across all autoimmune disorders, except for rheumatoid arthritis, the researchers found a consistent increase in the risk of psychosis among people with an autoimmune disorder. However, the strength and direction of this relationship varied between different disorders. 

While the study cannot explain the link between the mental and physical conditions, there are a number of possible mechanisms that might be involved. With the link between autoimmune disorders and psychosis beyond doubt, research is underway to understand why this might be the case.

‘Inflammation is one likely candidate given that people with psychosis show higher levels of inflammatory markers than healthy individuals, and inflammation is a core feature of autoimmune disorders. However, other factors such as shared genes, autoantibodies targeting brain proteins, and infectious agents might also play a role, ’ says Dr Cullen. 

'Whilst the mechanisms underlying this association remain unclear, this work suggests that careful monitoring of individuals with specific autoimmune diseases for early signs of psychosis is warranted. This is important, because we know that early intervention can improve clinical outcomes for people in the initial stages of a psychotic disorder.' 

Reference

'Associations Between Non-Neurological Autoimmune Disorders and Psychosis: A Meta-Analysis' by Cullen et al, Biological Psychiatry, 2018 DOI: 10.1016/j.biopsych.2018.06.016

Contact

For further media information please contact: Robin Bisson, Senior Press Officer, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, robin.bisson@kcl.ac.uk / +44 20 7848 5377 / +44 7718 697176.