Can brain scans diagnose mental disorders?

Why don't we use MRIs to diagnose depression?
04 February 2020


Brain cartoon



Can brain scans diagnose mental disorders?


We put this one to neuroscientist Camilla Nord...

Camilla - It's a very reasonable question and one from a research perspective that I'm very interested in, but from a clinical perspective, my answer's a bit like the male and female brain answer, which is that at a group level, there are several reproducible differences between brains with say, major depressive disorder and brains without. And this is on an anatomical level, but it's also on a level of kind of connectivity or function of different regions in the brain. So there are lots of different scales at which we can measure those group differences, but at the moment there aren't reliable differences that we could use to categorise a brain into one category or the other. And that's a sort of scientific problem. But then there's also, I would argue, a kind of clinical problem, which is what do you do with a false positive? If somebody has a depressed brain but they're not depressed, then that's meaningless.

Chris - So you have to say to them, well you should be depressed but you're not?

Camilla - Quite. So we would always need this criterion of functional impairment which exists at the moment in diagnoses and which could never be replaced by brain scan. Even if as I hope they become much more useful in the treatment of mental health disorders.

Chris - That said some degenerative disorders, or some things like schizophrenia for example, they are associated with changes in the shape and structure of the brain in the longterm, aren't they? So you can look at a brain scan, you can see that something has changed. You wouldn't necessarily know that that person has schizophrenia, but you could see that there were structural changes to the brain. In some people.

Camilla - Yes, the same would be true of major depressive disorder, but it wouldn't necessarily be the same changes in every single person with that disorder, which is an issue.

Chris - Do you think there's a likelihood we'll get a test in the future that could be based on imaging for things like depression, because there's a lot of people who really are depressed, but there are lots of people who they know at the moment the doctors struggle to actually do a definitive test for this diagnosis. So they might be tempted to say, Oh, I've got anxiety and depression and actually they don't because they know that they can get away with it. The people who are seeking to subvert the system, is there any way that perhaps in the future we could have a test that will enable us to do this?

Camilla - I think there are two things that brain scans could be really useful for in diagnosing and treating mental health disorders, but it's not exactly identifying whether or not you have one. The first is in redeveloping our categorisation of different mental health disorders. So at the moment, no two people with depression are exactly the same on neural level or on a, on a kind of clinical level. And in fact, on a clinical level, you can have two patients who don't even share a single symptom in common and yet get the same diagnosis. So that's where I really think brain scans could be more useful, in helping us delineate those categories a bit better. But the second area is something that I'm very interested in is trying to find out if brain scans could tell us more about which brains respond to which treatments.

Sam - So changing tack slightly, um, it's the super bowl tonight, I think. A lot of American footballers are suffering brain damage from repeat collisions. And they were saying they, they were detecting this post-mortem by looking at slices of brains. Do you know what they're doing in that case and what they're looking for?

Camilla - Yeah, I went to this great talk on that about a year ago, , from a lab that does that in Boston. So the PI of that lab had developed this way of pathologically categorising brains and she found almost like neurodegeneration, like what you might see in disorders like Alzheimer's or Parkinson's. But in people who'd suffered repeated concussions. And so it looked like their brains were aging at a really rapid rate even when they were actually quite young. And then they went on to develop sort of dementia like symptoms at a very young age and some of them even suffered very early deaths. Now she suffered a huge kind of media firestorm when this first came out because football is very well funded in the U S and people were not very happy with her conclusions, but her data, it's now been many, many years and it seems incredibly robust and sadly very believable.

Chris - So it's one thing to watch out for. And certainly we've had other people on this program including Graham McShane who has been commissioned to try to design structures for helmets that would dissipate some of the energy from these repeated injuries and also in just soccer, people heading balls is said to be sufficiently, uh, damaging to your brain when you do it professionally, that you do end up with a more rapid aging of the brain under those circumstances. So it's very important point and thank very much for that, Sam.


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