Schizophrenia, Bipolar Disorders and Co: Mental Illness with a Common Basis
As researchers have now found, mental illnesses can have important molecular similarities that are not reflected in the current diagnostic categories. In the long term, the new findings could contribute to improving the diagnosis and therapy of affected patients.
Mental illnesses are common
According to health experts, roughly every fourth person suffers from a mental disorder such as depression at some point in their lives. Scientific studies have shown that we all have the facilities for this. A new study has now provided more insights into the causes of such diseases.
Psychiatric disorders share numerous genetic factors
As the Rheinische Friedrich-Wilhelms-Universität Bonn reports in a current communication, psychiatric illnesses such as schizophrenia and bipolar disorders occur in families.
Scientists from the Brainstorm Consortium with the participation of human geneticists from the University Hospital Bonn have now carried out a study to investigate the genetic connections between these disorders and other brain disorders in a system that far outshines previous work on this topic.
The international team of scientists found that psychiatric disorders share numerous genetic factors, while neurological diseases such as Parkinson's or Alzheimer's appear to be more clearly differentiated in terms of their genetic basis.
Important similarities at the molecular level
The study, now published in the journal "Science", dealt with the question of how genetic variation is linked to the development of brain diseases.
The results suggest that psychiatric disorders are likely to have important similarities at the molecular level that are not reflected in the current diagnostic categories.
International consortia reportedly pooled their data to study the genetic patterns of 25 psychiatric and neurological disorders.
"This large-scale study was only possible through the worldwide collaboration of various researchers in the field of psychiatric and neurological diseases," says Prof. Dr. Markus Nöthen, Director of the Institute for Human Genetics at the University Hospital Bonn.
"It is currently one of the largest genetic studies in patients and controls worldwide." More than 500 scientists worldwide worked on the large-scale study, including seven employees from the Bonn Institute for Human Genetics.
Far-reaching genetic overlaps
Since each individual genetic variant only makes a small contribution to the development of the disease, the analyzes required large samples to reliably separate signals from noise.
Using genome-wide association studies on a total of 265,218 patients and 784,643 controls, the researchers determined the extent of the genetic overlap between the individual diseases.
The Bonn researchers contributed to the study by examining the genome of several thousand patients with schizophrenia, bipolar disorder and depression, as well as several thousand healthy controls.
The results showed extensive genetic overlaps in various mental illnesses, particularly between attention deficit hyperactivity disorder (ADHD), bipolar disorder, severe depression and schizophrenia.
In addition, the data show a strong overlap between anorexia nervosa and OCD and between OCD and Tourette syndrome.
In contrast, neurological disorders such as Parkinson's and multiple sclerosis were more distinct from each other and from psychiatric disorders - with the exception of migraines, which are genetically related to ADHD, severe depressive disorder, and Tourette syndrome.
Do the clinical diagnostic criteria need to be revised?
According to the scientists, the pronounced genetic overlap between the psychiatric disorders indicates that the current clinical diagnostic criteria do not exactly reflect the underlying biology.
"The results of the study could therefore lead to the diagnostic categories of mental illnesses having to be restructured in the future," says Dr. Franziska Degenhardt, head of the working group "Genetics of schizophrenic disorders" at the Institute for Human Genetics at the University Hospital Bonn.
For example, a single mechanism that regulates the amount of a protein in the brain could affect both inattentive behavior in ADHD and impaired function in schizophrenic disorders.
"In the long term, further research into these genetic relationships could help to improve the diagnosis and therapy of patients with neuropsychiatric disorders," said Dr. Andreas Forstner, who, together with Prof. Nöthen, heads the Bonn working group on mood disorders involved in the study. (ad)