Mental illness untangled?
Every year one in four people in the UK suffers from mental illness and the level appears to have increased considerably during lockdown.
In general, each case is labelled with one out of the hundreds of diagnoses listed in the Manual of Mental Disorders and given the appropriate treatment. But several recent findings have left psychiatrists wondering if this strict disease categorisation is valid.
Predisposition to mental illness is regarded as roughly 50 per cent environmental and 50 per cent genetic. Experiences such as childhood abuse and other mental traumas, as well as drug and alcohol dependency, are important environmental factors.
Similarly, a family history of, say, schizophrenia, increases the chances of developing the disorder.
But puzzlingly, these risk factors, whether genetic or environmental, are not specific for one disorder but increase the chances of developing many forms of mental illness. This suggests the underlying pathological processes involved in these disorders are in some way linked and recent genetic studies corroborate this suggestion - see references 1, 2 below.
Genetic factors explaining disease inheritance of neurological conditions like multiple sclerosis, Alzheimer’s and Parkinson’s diseases are clearcut, with specific gene variants identified that increase the risk of disease in families with a strong history of the disease.
But this is not the case with psychiatric conditions. Indeed, no single genes linked to individual psychiatric disorders have been discovered.
Rather, scientists have identified associations common to several different disorders. For example, there are strong links between schizophrenia and bipolar disorder, between anorexia nervosa and obsessive-compulsive disorder and between anxiety disorder with major depressive disorder.
These findings strongly imply that psychiatric disorders are not distinct entities but merge into a spectrum of linked disorders with common pathologies.
The challenge is to understand the biological and pathological processes underlying these common risk factors. This is a demanding and longterm undertaking, but the results could be game-changing.
They will open the door to identifying drug targets or maybe even a single common target for the development of drugs that will benefit people with many different mental disorders.
References: 1 Jones, D New Scientist, January 25 2020; 2 Marshall M Nature, 581. 19-21. 2020