Can Our Genes Lead to Mental Illness?
Scientists have successfully mapped how genes are expressed differently in the brains of people with one of five major psychiatric disorders, providing a much needed deeper insight into how our genes influence our risk of developed mental illness, for the first time.
The study, published in Science, involved 700 people in total. An international coalition of researchers sorted through data from earlier studies that analysed the genetic makeup of people’s brains, donated at death, who were diagnosed with either clinical depression, schizophrenia, autism spectrum disorder, alcoholism, or bipolar disorder.
The researchers looked for the specific RNA molecules found within these people’s brain cells in the cerebral cortex, which “read” and translate the DNA packed into every cell. This allowed them to see and map out how the cells actually carried out the genetic instructions that were coded with. The last step involved using the brains of people with a non-psychiatric condition, irritable bowel disorder, as a control group.
As a result, they discovered lots of distinct overlaps of molecular activity between the brains of people with psychiatric disorders that weren’t found in “healthy” brains, indicating that many of the same sorts of biological dysfunctions underpin them.
“These findings provide a molecular, pathological signature of these disorders, which is a large step forward,” explained senior author, Daniel Geschwind, a professor of neurology, psychiatry, and human genetics and director of the UCLA Centre for Autism Research and Treatment.
The findings may change how we conceptualise certain mental illnesses. For example, the molecular signature seen in people’s brains with bipolar disorder was the most similar to those with schizophrenia. This came as a surprise to the researchers since the symptoms of each tended to be very different from one another.
In addition, there were some vital differences. The brains of people with alcoholism shared almost nothing in common with anyone else’s. That discounts previous research suggesting that depression and alcoholism are often genetically connected. The same goes for depression, which had many patterns of molecular activity not found with other disorders. Such distinctions are essential, as they have the potential to one day help scientists develop better diagnostic tests, explained the researchers.
It isn’t just genes that influence how a cell performs, or even fails its assigned job; the environment we spend our lives in also plays a role. Unfortunately, there isn’t one single genetic mutation that will ever explain why someone is prone to depression. But, scientists now understand that a person’s genetic risk of mental illness derives from lots of almost-insignificant genetic variations-some which are incredibly common, and some rare – that interact with each other in ways we simply don’t know right now.
The real work is yet to come.
“We show that these molecular changes in the brain are connected to underlying genetic causes, but we don’t yet understand the mechanisms by which these genetic factors would lead to these changes,” added Geschwind. “So, although now we have some understanding of causes, and this new work shows the consequences, we now have to understand the mechanisms by which this comes about, so as to develop the ability to change these outcomes.”