The Chronicle Herald (Provincial)
Study examines genetic links of disorders
The results of a new research project show some psychiatric disorders share common genetic links, a discovery that could help clinicians and patients in their approach to treatment and expectations.
Dalhousie University’s Dr. Sandra Meier, who is one of the study’s coauthors, said the researchers looking at 11 major psychiatric disorders basically examined the genetics of mental illnesses. The project offers new insight into why comorbidities – the simultaneous presence of two or more conditions in patients – are common.
The study was recently published in the journal Nature Genetics.
“What we know is that we can often see that person (who) has one disorder potentially has another one,” Meier said during an online interview conducted via Zoom.
Also, within families, multiple issues can sometimes be seen, such as a parent has bipolar disorder and a child has depression.
The researchers used data from thousands of subjects in genome association studies that examine every single marker that a person has in their genome that occurs over a certain frequency.
“We looked at that and looked, for example, at people with bipolar disorder – thousands of people with bipolar disorder – and correlated that with the genetic underpinnings of thousands of people who had ADHD or depression and looked at how much of that is actually shared,” Meier said.
The results of the study, which involved researchers from Dalhousie as well as from the U.S., U.K., the Netherlands, Denmark and Germany, revealed that the majority of genetic underpinnings were shared between illnesses – some of them strongly.
Meier said a lot of linkage theories doctors have had through their clinical practices are now shown to be true and can be at least partially explained through genetics.
The link between bipolar and schizophrenia is well-known, she added. But there are other things that might not be as well known.
“For example, we found that new developmental disorders like autism and ADHD have actually quite strong connection to depression and PTSD, although we know that that happens in adulthood … (when) diagnosed with ADHD as adults, it’s likely that they’ll suffer depression but it seems also connected to childhood onset … especially PTSD. It’s really understudied, so I think that’s something new that we found that is really important and it also triggered a lot of researchers to look more closely at that.”
Other connected disorders include anorexia nervosa, obsessive-compulsive disorder, and major depression and anxiety.
She said it’s important for patients to talk with their clinicians about how they want to handle things.
INFORMED DECISIONS
Heavy use or abuse of substances can make people more vulnerable to a lot of mental health issues, she noted. So for someone who already has depression, if they drink a lot of alcohol, that can increase the risk for other mental illnesses.
“I want patients to be informed about their decisions, so yes, if you want to drink – we don’t say that you should not drink – but just be aware that it should be in lower amounts.”
Some patients might want to talk with their clinicians about family connections with a particular disorder, their concerns that they might also develop it, and ask what they can do about it. Both sides can then work on it together, Meier said.
“I think just knowing that, acknowledging it and then working with patients on their individual solution – maybe some patients don’t care – but when they want something like that, I think it’s important we do that.”
STILL ENVIRONMENTAL FACTORS
But, Meier stressed, people should not feel that a genetic link means a guarantee of the disorder manifesting. Environmental factors are also strongly involved.
“Genetics is one point, but you can be genetically vulnerable and everything in your life goes absolutely perfect and you will never develop an illness. Or it could be that you have low risk but then a lot things may happen in your life that are really bad, like the pandemic. I think that was something nobody foresaw and that definitely increased issues in families.”
One thing Meier does not want to do is “freak out” patients who will worry that comorbidities ruin their lives.
“Yes, comorbidities are the rule and many patients can develop comorbidity, but it doesn’t have to be.
“Yes, it means that a lot of the genetics are shared but it doesn’t mean that you will develop all of these mental illnesses. What it rather means is that you have a vulnerability and then your specific individual risk factors make you more likely to develop schizophrenia or bipolar disorder, but (while) you share something like 70 per cent of your genetics with someone who has schizophrenia … you also share a lot of your genetics with people who are totally healthy.”
CONCLUSIONS
“I think what is important for us as researchers is to acknowledge that we should not look at a single disorder on its own, but more together,” Meier said.
“I think that’s very, very important, that we consider illnesses as something dimensional and not looking at bipolar disorder and say that you will never go on to develop schizophrenia. It’s unlikely that you will develop it, but some of them will develop it.”
That awareness could help clinicians know that a changing diagnosis is not necessarily an error and prepare them for the need to adapt treatment.
“It’s more complex than our potentially narrow-minded view,” she added.
Meier`s husband and fellow Dal associate professor Manuel Mattheisen was also a co-author of the study.