Genetics of mental illnesses like depression, OCD: New research …

sad woman depressed lonely girlShutterstock

  • Scientists are uncovering promising links between
    specific parts of our DNA and a range of disorders such as
    anxiety, depression, and obsessive-compulsive
  • As with any disease, having certain genes or
    mutations in those genes doesn’t mean you’ll go on to develop
    the disorders, but it may play a key role.
  • The research also helps highlight the biological
    underpinnings of mental illness, something that could help with
    the development of better treatments.


When you fall and break a bone, an X-ray shows the crack. There’s
no equivalent diagnostic for disorders of the brain — a shortfall
that’s made it difficult for millions of people with conditions
ranging from anxiety to obsessive-compulsive disorder to get

A spate of new research may change that. In a handful of recent
studies, scientists have identified what they believe to be some
of the most reliable genetic hallmarks of mental illness, a
discovery that would transform our current approach to treating
the disorders. If we can better understand the genes
that influence psychiatric diseases, we can design
treatments that accurately target the part of the brain that
they appear to effect.

“Beyond giving us so much data to explore, being able to show
that depression is a brain disease, that there is biology
associated with it, I think that’s really critical,” Roy
, the director of the Center for Experimental Drugs and
Diagnostics at Massachusetts General Hospital,
told Business Insider
in 2016. “These are brain diseases,
like any other. They’re not someone’s fault.”

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The latest research suggests that our DNA may play an
outsize role in psychiatric disease. As far as diseases go,
mental illnesses are among those that are the most likely to be
passed down from parent to child, a finding only
recently illuminated
by decades of research. 

“Genetics plays a very big role in your risk of getting these
diseases,” Elinor
, a geneticist at the Broad Institute of MIT and
Harvard University, told Business Insider. 

Still, looking at someone’s genome alone will probably
never be enough to determine if they’ll go on to
develop a psychiatric disease — other factors, including
environmental factors like severe stress, play a strong
role too. But scientists are discovering more and more clues that
suggest that the key to discovering new treatments for mental
illnesses will center on a deeper dive into our DNA.

“We need to go after this genetic component,” Karlsson said.

In the summer of 2016, Perlis used data from 23andMe to

pinpoint 17 genetic variants linked with major depressive
. But Perlis and 23andMe aren’t the only ones making
progress in this arena. Earlier this month, researchers at the
University of Massachusetts and the Broad Institute identified
four genes linked to obsessive-compulsive disorder (OCD), a
chronic condition characterized by uncontrollable
repetitive thoughts and behaviors. 

‘People who have OCD are more likely to have these changes in
these genes’

Hyun Ji Noh, a geneticist at the Broad Institute, has read lots
of studies showing a link between OCD and genetics. Despite all
this promising research, none of the existing papers came to any
definitive conclusions about which genes seemed to be tied to the

So for her latest study, published earlier this month in the
journal Nature Communications, she decided to try a different

Instead of just focusing on human DNA, which in the other
studies had yielded limited results, she looked at
multiple sets of genes — and not just from humans. 

“There are a lot of naturally occurring dog diseases — especially
psychiatric diseases — that are very similar to human diseases,”
Hyun Ji Noh, a geneticist at
the Broad Institute and the lead author on the study, told
Business Insider. “So to me it was sort of natural to put
dog studies in the context of human disease.”

alone sad depressed sea

Noh’s paper looked at hundreds of genes that had been
implicated in psychiatric disease in dogs, mice, and people.

In humans, the researchers found 608 genes. To find out
which of these 608 genes was actually tied to OCD, Noh
compared what they looked like in hundreds of
people with and without the disorder. By the end of the analysis,
just four genes emerged that showed up repeatedly in mutated form
in people with OCD. 

In these four genes, “a lot of mutations kept showing
up for OCD patients but not in the healthy individuals,” Noh

In other words, these four genes likely play a key role in
the biology of the disorder. Still, having a mutation in one of
these four genes doesn’t necessarily mean you’ll go on to develop

“We know people who have OCD are more likely
to have these changes in these genes. But this is one
of potentially 100 things that will determine if you have OCD,”
said Karlsson, who also worked on the paper. “It’s complicated,”
she said.

Chasing ‘depression genes’

Like OCD, researchers say depression is influenced heavily by our
DNA. But unlike OCD, it’s fairly common, occurring in
an estimated 16.1 million Americans
. Current treatments
for depression haven’t changed much since the 1950s, and they
don’t work for everyone.

So, in an effort to find out more about what exactly causes the
illness, researchers published a paper in the summer of
2016 in the journal Nature Genetics in which they
pinpointed 17 genetic variations, or tweaks in particular genes,
that appear to be tied to major depressive disorder, the most
debilitating form of the disease that’s currently
the leading
cause of disability worldwide

The researchers got their data from personal genomics
company 23andMe. 

Using data from more than 75,600 people who told the company
that they’d been clinically diagnosed with depression and more
than 231,700 people who reported no history of depression, Perlis
and his team were able to identify 17 areas on DNA that appear to
be linked with depression. They also found some ties between
these areas and those which have been previously identified
as possibly playing a role in other psychiatric disorders,
such as schizophrenia.

Scientists have been looking for such genetic
hallmarks of depression for years
. And while some, like
a 2013
study in the journal The Lancet
and a
2015 paper in the journal Nature
, have
yielded promising clues, none have been able to spot any
precise, reliable genetic markers of the disease.

At least
not until now

“My group has been chasing depression genes for more than a
decade without success, so as you can imagine, we were really
thrilled with the outcome,” Perlis said.

The hope is that identifying these watermarks in our DNA — tiny
areas on genes where high amounts of variation tend to occur
among individuals — will help us better understand how
genetics and behavior interact to influence disorders like

Still, Perlis said, “this is really just the beginning. Now
the hard work is understanding what these findings tell us about
how we might better treat [these disorders].”