For nearly a century, the two separate diagnoses of schizophrenia and bipolar disorder have been used to differentiate between symptoms, outcomes and more recently, response to medications. A growing number of researchers, however, are starting to question whether these are useful tools for the classification, understanding, and treatment of major mental illness.
“We have known for a long time that the clinical symptoms are shared substantially between the two conditions, but when you look at the biology, these illnesses also blur into each other,” said Godfrey Pearlson, professor of psychiatry and neurobiology at Yale School of Medicine and a co-author of the studies.
“It is clear that they are not two nicely separated packages, but there is a substantial crossover between the two.”
Although researchers have not found clear-cut genetic culprits, they have known for years that schizophrenia and bipolar patients share similar abnormalities in such measures as eye movement and response to electroencephalogram tests. Similar problems are often detected in their healthy close relatives as well.
Scientists at Yale and the Institute of Living in Hartford, Conn. — as well as four other sites in Massachusetts, Illinois, Texas and Maryland— are conducting a study known as BSNIP (Bipolar-Schizophrenia Network on Intermediate Phenotypes).
The researchers are looking into 20 potential biological disease factors in 3,000 participants. The subjects include those with schizophrenia and psychotic bipolar disorder, as well as their close relatives and unrelated healthy controls.
The research is revealing similar deficits in the brain among grey matter (neurons) and white matter (neuronal projections and connective cells) among schizophrenia and bipolar patients. Also, the two disorders share similar types of cognitive deficits.
There are no clear-cut biological distinctions separating the two disorders. In fact, similar brain abnormalities and cognitive dysfunction is shared to a lesser degree by relatives of the patients and most likely represent disease susceptibility.
The research may eventually point to the common genetic causes of these deficits. Pearlson noted that the National Institute of Mental Health recently proposed a reclassification of mental illnesses based on biological factors.
Source: Yale University