For many years, scientists have studied mental health and brain development disorders one by one.
Conditions such as autism spectrum disorder, attention-deficit/hyperactivity disorder, schizophrenia, bipolar disorder, depression, and insomnia can look very different from each other.
People with autism may struggle with social communication and repetitive behaviors. Those with ADHD often have problems with attention and impulse control.
Schizophrenia can affect thinking and perception, while bipolar disorder involves major shifts in mood and energy. Depression can cause long-lasting sadness and loss of interest, and insomnia makes it difficult to sleep.
Even though these conditions have different symptoms, scientists have long wondered whether they might share some hidden biological causes.
Researchers from Fudan University, King’s College London, University Paris-Saclay, and several other institutions have now carried out one of the most comprehensive studies to investigate this question. Their findings were published in the journal Nature Mental Health.
The research focused on both genetics and the immune system. In recent years, scientists have increasingly recognized that the immune system and the brain are closely connected.
Problems in the immune system have been linked to several psychiatric and neurological disorders. Some studies have even found that people with autoimmune diseases are more likely to develop certain mental health conditions.
To explore these connections, the researchers analyzed blood samples from 1,274 healthy teenagers who participated in the IMAGEN project, a large European research program.
The teenagers had no diagnosed mental health conditions, which allowed the researchers to study normal biological differences and determine whether some patterns were associated with a higher risk of developing mental health disorders.
The team looked at genetic changes called single nucleotide polymorphisms, which are tiny variations in DNA that naturally occur among people.
They also studied DNA methylation, a process in which small chemical tags attach to DNA and influence how strongly genes are turned on or off. Gene activity can be altered by these chemical tags without changing the DNA sequence itself.
After performing extensive analyses, the scientists identified 73 DNA methylation sites and 62 genes that appeared to be linked to major neuropsychiatric disorders. Some of these biological markers seemed to be unique to individual conditions, while others were shared across several disorders.
The researchers then made another important discovery. They found three genes that appeared to play especially important roles. These genes, called MAD1L1, MRPL2, and HLA-DRB1, may act as key links between changes in DNA methylation and the biological pathways involved in several different conditions.
One gene, MRPL2, was linked to both insomnia and schizophrenia. The researchers found evidence that certain DNA methylation changes reduced the activity of this gene, which may contribute to the risk of developing these conditions. Meanwhile, higher activity of MAD1L1 and HLA-DRB1 appeared to increase the risk of schizophrenia.
Interestingly, many of the genes identified in the study were also involved in pathways related to autoimmune diseases. This finding suggests that some mental health disorders and immune disorders may share parts of the same biological foundation.
The study does not mean that these genes directly cause mental illness. Mental health conditions are extremely complex and are influenced by many factors, including genetics, life experiences, stress, environment, and early development. However, the findings provide important clues about the underlying biology of these disorders.
The research also raises exciting possibilities for the future. If scientists can better understand the biological pathways that several disorders have in common, they may be able to develop new treatments that target these shared mechanisms.
In addition, doctors may eventually be able to use biological markers to identify people at higher risk and provide earlier interventions.
The study’s strengths include its large number of participants and its use of advanced genetic and molecular techniques. However, there are also limitations.
The study mainly used blood samples from healthy adolescents rather than brain tissue from patients with diagnosed conditions. Therefore, further research is needed to confirm exactly how these genes function inside the brain and how they contribute to disease development.
Overall, this research provides one of the clearest pictures yet of the biological links that may exist among different psychiatric and neurodevelopmental conditions. It suggests that disorders that appear very different on the surface may share important molecular pathways deep inside the body.
These discoveries could eventually improve diagnosis and lead to more personalized and effective treatments for millions of people worldwide.
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Source: Fudan University.
