Last updated August 2, 2018 at 10:52 am
Having a common basis could help researchers home in on the biological mechanisms at play.
Some traits always seem to go hand in hand. A towering Dane weighs more than an Indonesian, for instance, because many of the same genes influence both height and weight.
Now, a massive study taking in genomic data from more than 1 million people has shown that the same genetic overlap occurs in certain brain disorders.
The analysis, lead by Verneri Anttila at the Broad Institute of MIT and Harvard, lumped together data from 17 different brain disorders gathered by members of an international collaboration called the Brainstorm Consortium.
Added to this were data from an additional 1.2 million-odd genomes on brain-related attributes such as personality traits and intelligence, as well as non-brain measures including height, weight and coronary artery disease.
While rare gene mutations can cause some brain disorders, such as epilepsy and autism spectrum disorder, multiple common genetic variants can also conspire to increase a person’s disease risk.
This study asked whether the same common variants might be responsible for multiple disorders at once.
The researchers found that psychiatric disorders, such as attention deficit hyperactivity disorder (ADHD), bipolar disorder, major depressive disorder (MDD) and schizophrenia, had considerable genetic overlap.
On the other hand, neurological conditions – disorders marked by observable phenomena such as protein clumps or blood clots, or aberrant electrical activity – such as Alzheimer’s disease, epilepsy and multiple sclerosis were more genetically distinct from one another and from the psychiatric disorders.
Migraine was an exception. Its genetics overlapped with ADHD, MDD and Tourette syndrome.
Meanwhile, the personality trait of neuroticism overlapped with nearly every psychiatric disorder as well as migraine.
The study suggests that in the case of psychiatric disorders, instead of there being a ‘gene for depression’ or a ‘gene for schizophrenia’, it’s likely that a combination of variants from the same genomic neighbourhoods underlie both conditions.
Knowing that two disorders share a common genetic basis could help researchers hone in on the underlying biological mechanisms at play.
It could also force a rethink of whether some disorders, currently classified as distinct conditions in the clinic, are actually more closely related than we realise.