What causes ADHD? New study links potential risk genes to disorder

A new study has linked potential risk genes to ADHD, potentially furthering research on what causes one of Canada's most common and often misunderstood neurodevelopmental disorders. (Pexels)

While previous research has linked genetic factors to the cause of Attention Deficit Hyperactivity Disorder (ADHD), there is yet to be conclusive evidence to identify the specific genes that can cause the neurodevelopmental disorder.

However, a new study out of Denmark is getting closer to identifying these specific genes and why ADHD can develop in some and not others.

The study, published in the peer-reviewed journal Nature Genetics in January, analyzed data on more than six million genetic variants in 38,691 people with ADHD and 186,843 people without the disorder. The researchers were able to identify 27 variations in the human DNA code that were most present in people with ADHD; however, they estimate there could be as many as 7,300 of these genetic variants.

The study also indicated genes linked to ADHD often have a high level of gene expression in brain tissues during the brain development stage as early on as the embryonic stage, which is between the fifth and 10th week of pregnancy.

“This emphasizes that ADHD should be seen as a brain developmental disorder, and that this is most likely influenced by genes that have a major impact on the brain’s early development,” lead study author Ditte Demontis said in a news release.

According to the Centre for ADHD Awareness, Canada, the most common symptom of ADHD is a reduction in attention span and concentration. People with ADHD can experience being hyperactive by talking excessively or being impulsive, while others can be inattentive and some can experience a combination of both. In Canada, ADHD affects an estimated 1.8 million people.

The study found that these risk genes often affect dopaminergic neurons, which play a major role in a person's behaviour, affecting their mood, stress or a variety of feelings. Researchers also combined their results with data from 4,973 people that underwent neuro-cognitive tests and found these genetic variants can be linked to a person's reduced attention span, short-term memory, and reduced reading and mathematical ability.

HOPE FOR MORE PERSONALIZED MEDICATION

Amori Mikami, clinical psychologist and professor of psychology at the University of British Columbia, says this study could potentially help further diagnosis and treatment of ADHD. In particular, it could help reduce the stigma behind it.

"There is a lot of stigma about ADHD in the public and I do think some of it can be due to people not believing that ADHD is a real disorder," Mikami said in a phone interview with CTVNews.ca on Thursday.

"I'm glad that these researchers are doing this genetic research because we need more science to understand the causes of ADHD."

Similar studies diving into the science of ADHD could also pave the way for more personalized medicine, she said. While treatment for ADHD varies, Mikami explains it often involves prescribed medication along with psychotherapy to help with behavioural treatment.

However, because there are various medications used to treat ADHD, the process to find the right one can be long and frustrating since the side-effects can vary from person to person.

"For families and people with ADHD, there's so much trial and error in medication and it can be very discouraging, frustrating and time consuming," she said.

"We're still a long way from that but I do think that those are some exciting potential implications down the road."