Specifically, some similar patterns of gene expression were found in people with autism, schizophrenia and bipolar disorder, the researchers say.
Gene expression refers to cells' conversion of genetic instructions into proteins.
"These findings provide a molecular, pathological signature of these disorders, which is a large step forward," said senior study author Daniel Geschwind.
"The major challenge now is to understand how these changes arose," added Geschwind, director of the University of California, Los Angeles' Center for Autism Research and Treatment.
"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," Geschwind said in a university news release.
His team analyzed the RNA in 700 tissue samples from the brains of dead people who had autism, schizophrenia, bipolar disorder, major depression or alcohol abuse disorder. They compared the samples with samples from brains of people without mental illness.
While there was significant overlap in gene expression patterns associated with conditions such as autism and schizophrenia, people with major depression had gene expression patterns not seen in other types of mental illness, the researchers said.
Now that the researchers have some understanding of causes, the next step is to understand the underlying mechanisms "so as to develop the ability to change these outcomes," Geschwind said.
The study was published Feb. 8 in the journal Science.
SOURCE: University of California, Los Angeles, news release, Feb. 8, 2018
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