Genetics Sheds Light on Psychiatric Illness

Progress in understanding psychiatric conditions such as schizophrenia and autism was poor during the 20th century and science yielded few treatments. However, genetics is shaking up our understanding of these illnesses, says Dr Kevin Mitchell in Trinity College Dublin, who studies the genetics behind brain wiring.

“Genetics diagnosis is going to transform psychiatry into a truly modern branch of medicine,” he explains.

Until now, a patient was diagnosed with ADHD, autism, bipolar disorder or schizophrenia by talking to them about their experiences. There is no MRI scan, blood test or endoscopy to pinpoint a cause, so this was the only option.

Now it seems there is no one cause and each of these conditions is just a set of symptoms. To complicate matters, sometimes they morph from one to the other.

Geneticists have begun to get to identify the genes causing the problems in different individuals.

“There are maybe 500 different genes involved in these conditions, each of which can mutate and cause a disease like schizophrenia or autism. So rather than thinking about them as one disease, we now see them as multiple disorders,” Mitchell adds.

Four people diagnosed with bipolar disorder might all have different gene mutations. This means one therapy will not necessarily work for each individual.

The conditions are linked though. “Many of the mutated genes have a role during the development of the brain and in specifying connections nerve cells make with one another,” according to Mitchell. For example, genes make proteins that help guide nerve cells into place and allow them form vital connections with one another.

“These proteins are involved in the strengthening of nerve cell connections and many of these disorders are disorders of these synaptic connections,” he says. A faulty gene results in a dysfunctional protein, which leads to connection failures.

The brain relies on very complex circuitry and a lot can go wrong when there are thousands of different types of brain cells with different jobs. Mitchell’s lab is among those unravelling this complexity.

“Recently we discovered a gene whose function is to specify what type of connection is made between particular cells in the brain,” explains Mitchell. “Animals that do not have it experience seizures and symptoms like ADHD.”

This work was carried out by Mitchell’s colleague Dr Jackie Dolan.  

Genetic studies show psychiatric conditions are often caused by rare mutations. Today, scientists can pinpoint these mutations by sequencing an individual’s entire genetic make-up.

“Genetics will not lead to a cure overnight, but it will help with diagnoses. That is the first step of getting new drugs based on a rational understanding of these disorders,” Mitchell concludes.