Excerpts from “The Hidden Links between Mental Disorders” by Michael Marshall, Nature 581, 19-21 (2020) (https://www.nature.com/articles/d41586-020-00922-8).
“In 2018, psychiatrist Oleguer Plana-Ripoll was wrestling with a puzzling fact about mental disorders. He knew that many individuals have multiple conditions — anxiety and depression, say, or schizophrenia and bipolar disorder. He wanted to know how common it was to have more than one diagnosis, so he got his hands on a database containing the medical details of around 5.9 million Danish citizens. … Every single mental disorder predisposed the patient to every other mental disorder — no matter how distinct the symptoms.”
“… scientists have piled up an enormous amount of data over the past decade, through studies of genes, brain activity and neuroanatomy. They have found evidence that many of the same genes underlie seemingly distinct disorders, such as schizophrenia and autism…”
“… The idea that mental illness can be classified into distinct, discrete categories such as ‘anxiety’ or ‘psychosis’ has been disproved to a large extent. Instead, disorders shade into each other, and there are no hard dividing lines …”
“… most psychiatrists agree that one thing is clear: the old system of categorizing mental disorders into neat boxes does not work.…”
“… Since the 1950s, psychiatrists have used an exhaustive volume called the Diagnostic and Statistical Manual of Mental Disorders, currently in its fifth edition. It lists all the recognized disorders, from autism and obsessive–compulsive disorder to depression, anxiety and schizophrenia. Each is defined by symptoms. The inherent assumption is that each disorder is distinct, and arises for different reasons. … Few patients fit into each neat set of criteria. Instead, people often have a mix of symptoms from different disorders. Even if someone has a fairly clear diagnosis of depression, they often have symptoms of another disorder such as anxiety. …”
“Clinically, the evidence that symptoms cut across disorders — or that people frequently have more than one disorder — has only grown stronger. For this reason, although individual symptoms such as mood alterations or impairments in reasoning can be diagnosed reliably, assigning patients to an overall diagnosis such as ‘bipolar disorder’ is difficult.”
“Some psychiatrists are already trying to reimagine their discipline with dimensions in mind. In the early 2010s, there was a push to eliminate disorder categories from the DSM-5 in favour of a ‘dimensional’ approach based on individual symptoms. However, this attempt failed — partly because health-care funding and patient care has been built up around the DSM’s categories.…”
“The studies reveal that no individual gene contributes much to the risk of a psychopathology; instead, hundreds of genes each have a small effect. A 2009 study found that thousands of gene variants were risk factors for schizophrenia. Many were also associated with bipolar disorder, suggesting that some genes contribute to both disorders.”
“There are already hints that generalized treatments could work just as well as targeted therapies. A 2017 study randomly assigned people with anxiety disorders, such as panic disorder or obsessive–compulsive disorder, to receive either a therapy for their specific disorder or a generalized approach. Both therapies worked equally well.”
The complete article, including references, is available at https://www.nature.com/articles/d41586-020-00922-8.
Last updated in June 2020.