Schizophrenia and Bipolar Disorder Share Genetic Roots
A trio of genome-wide studies—collectively the largest to date—have pinpointed a vast array of genetic variation that together may account for at least one third of the genetic risk for schizophrenia, a brain disorder that's symptoms can include hallucinations, delusions and disordered thinking. One of the studies traced schizophrenia and bipolar disorder (an illness that causes shifts in a person's mood, energy and ability to function) in part, to the same neighborhood of genes.
Balintfy: Three genetic research studies, appearing on-line in the journal Nature, are showing that schizophrenia may share the same genetic roots as bipolar disorder.
Insel: This new set of studies builds on a hint that we had before that the genetic risk for schizophrenia may overlap the genetic risk for bipolar.
Balintfy: Dr. Thomas Insel is the director of the National Institute of Mental Health. Insel: We don’t have a smoking gun here, and I think the one thing you can say from these three studies is there isn’t going to be a smoking gun. And it’s only in very rare cases that you’re going to find a large-effect gene that actually could be considered to be a cause rather than just a risk factor.
Balintfy: Though all three studies implicate an area of Chromosome 6, most of the genetic makeup of schizophrenia, which is estimated to be at least 70 percent heritable, remains unknown. Dr. Insel says that the short arm of Chromosome 6 is a very interesting area.
Insel: In some ways it’s like the Bermuda Triangle of the human genome sequence because it’s an area with a tremendous amount of variability
Balintfy: He adds that this is an area of great complexity in the genome, previously associated with a number of autoimmune diseases, including type-1 diabetes, rheumatoid arthritis, and Crohn’s disease. And now it may be significant for schizophrenia.
Insel: We didn’t know that before, and so this is news, and it’s something that will be an important area for further study as we try to understand how there could be an autoimmune aspect to schizophrenia that at least plays out in terms of genetic risk.
Balintfy: Dr. Insel says the studies also remind that these disorders, that both cause psychosis, may have more in common, changing the thinking of the past century.
Insel: We’ve really been essentially dividing up psychotic illnesses into those, like schizophrenia, that are mostly about thought disorder, hallucinations and delusions, and those that are more about mood regulation like bipolar illness, which in an earlier form was called manic-depressive illness. It’s never been the case that it’s a perfect line for every subject. You do see people who seem to have elements of both. And these kinds of studies, looking at the genetic underpinnings, suggest that yes, you know, that even at the genetic level there may be more overlap than what we’ve thought.
Balintfy: The new findings could eventually lead to multi-gene signatures or biomarkers for severe mental disorders. Dr. Insel emphasizes that as more is learned about the implicated gene pathways, it may be possible to sort out what’s shared by, or unique to, schizophrenia and bipolar disorder. For more information on these studies and diseases, visit www.nimh.nih.gov. This is Joe Balintfy, National Institutes of Health, Bethesda, Maryland.
About This Audio Report
Reporter: Joe Balintfy
Sound Bite: Dr. Thomas Inse
Topic: schizophrenia, bipolar, bipolar disorder, gene, genetic risk