Depression and Dementia: Not Mutually Exclusive At All

Brain Yapping by Dr Dean Burnett

The recent release of a documentary about his final days has seemingly rekindled the dispute about whether Robin Williams was enduring dementia or depression. But it needn’t have been just one.

The argument about what Robin Williams was suffering from when he died is minor, but surprisingly persistent. It’s also meaningless. Pic by Shameek CC

When Robin Williams died by suicide in 2014, countless people leapt to the conclusion that it was a) due to depression, and b) he was selfish for ending his life in this way.

I, a neuroscientist, working as a psychiatry lecturer at the time, knew damn well this wasn’t how depression worked, and it was long past time somebody pointed that out. Luckily, I had a media platform (my Guardian blog) to hand, so I decided I would be the one to point that out. Hence, a did a quick blog, about why depression and suicide aren’t ‘selfish’, and it’s ignorant/cruel to insist otherwise.

A few days later, it had been read many millions of times, and it remains my most popular piece of writing to date. I was in tentative discussions with publishers about writing a book at the time, and my sudden viral success kicked their enthusiasm up several notches. And here we are today. In a way, you could say what success I’ve had, I owe to the death of Robin Williams. It certainly puts a bittersweet edge on it for me.

Since then, it’s emerged that, when he died, Williams’ was suffering from Lewy Body dementia. This was almost certainly a bigger factor in his suicide than more typical depression, something I addressed at length once this fact came to light. Even so, I still get the occasional online stranger ‘calling me out’ for getting it wrong, because it was ‘dementia, not depression!’, ergo, all my points about depression are invalid.

It’s an eyebrow-raising, and seemingly pointless, argument to want to have, so I’ve typically just ignored such anonymous wannabe-antagonists.

However, the recent release of the documentary ‘Robin’s Wish’, all about his final days, has dredged this whole issue up again. And I know that Cosmic Shambles ringmaster Robin Ince recently got into a Twitter spat about this, because he emailed me to check the specifics. And that’s why this article exists.

Essentially, there seem to be plenty of people out there under the impression that if someone has dementia, then they can’t have depression. And maybe vice-versa? And this impression is very wrong.

It’s 2021, and still the images you get when you google ‘depression’ are… weird.

Dementia and depression are indeed different things. Dementia is an umbrella-term for a range of disorders (mostly neurodegenerative in nature, but not always) whereby the brain becomes damaged, resulting in problems like memory loss and cognitive decline. Depression, on the other hand, is a mood disorder, where the brain isn’t ‘damaged’, per se; it’s just doing unhelpful things, which manifest in the familiar symptoms of depression. So, yes, dementia and depression are distinct diagnoses with differing mechanisms.

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But this doesn’t mean they’re mutually exclusive. Because they aren’t. And it doesn’t mean they can’t both occur in the same brain, because they absolutely can. And it doesn’t mean they’re completely separate things with no overlap, because that’s not correct either.

Firstly, there’s a high degree of comorbidity with depression and dementia (translation: they often occur at the same time, in the same person). It’s got to the point where there are specific tests to determine whether a patient’s symptoms are down to dementia or depression, because they often have similar symptoms, like poor recall, disrupted sleeping, lack of pleasure in enjoyable things, and more.

From a clinical perspective, it can be hard to tell the difference between dementia and depression. For instance, you’d typically use a cognitive assessment to look for symptoms of dementia; if a patient performs poorly on a basic test, if they’re unable to recognise or remember simple things, then it’s a sign of cognitive impairment, indicative of dementia.

Except, what if they perform poorly on the test not because they can’t remember or think of the answers, but because they’re in such a low mood they lack any motivation to do it right, or can’t see any point? This is a very likely outcome with depression. But the test scores look the same as if it was caused by dementia. And it’s really important to get the right diagnosis, because what treatment works for depression can make dementia worse, and vice versa.

You can know all the answers because you did the learning, or you can look them up online. The test itself doesn’t know, and the results can’t tell you how they were obtained.

Objectively, that dementia and depression would co-occur so often makes perfect sense; depression can often be the result of very stressful/traumatic experiences, and being officially diagnosed with dementia would certainly count as such. This presumably explains why you see a similar occurrence in cancer patients. So, far from being mutually exclusive, dementia could feasibly lead to depression.

This works both ways; depression is known to be a risk factor for dementia. Put simply, if you have depression, the odds of you eventually developing dementia go up, maybe as much as two fold or greater. This sounds scary, given how many people have depression, but it just means the relative risk is higher. As in, if you had a 3% chance of developing dementia given your biology, development etc., coming down with depression could increase that to 6%. But still, it’s something to be aware of.

Again, it makes scientific sense. Evidence shows that the grater your cognitive reserve (as in, the better shape your brain is in) as you age, the less likely you are to be afflicted by the symptoms of dementia, even if your brain’s structure shows clear signs of the pathology. But if there’s one thing that saps your brain’s resources and stresses it out, down to the neurological level. Ergo, a brain that’s spent a long time dealing with depression has less left in reserve to resist the onset of dementia.

There’s so much more to it all than this. The links between dementia and depression are many, complex, and still largely unclear. But it’s certainly safe to say that they are not mutually exclusive, that they can and do interact and affect each other.

If anything, the bigger question here is why would anyone insist otherwise? What’s to be gained from arguing, with no evidence, that the brain can’t possibly experience two serious problems at once? The only purpose it seems to serve is to undermine, and argue against, those who refer to the tragic plight of a household name to encourage more support and consideration.

Maybe that’s a priority for some people? How depressing, if so.

Dean Burnett covers issues like this and more, in his new book Pscyho-Logical, all about how mental health works in the brain, released February 4th.

Dr Dean Burnett is a neuroscientist and best selling author of such books as The Idiot Brain and The Happy Brain. His former column Brain Flapping for The Guardian (now Brain Yapping here on the CSN) was the most popular blog on their platform with millions of readers worldwide. He is a former tutor and lecturer for the Cardiff University Centre for Medical Education and is currently an honorary research associate at Cardiff Psychology School and Visiting Industry Fellow at Birmingham City University.  He is @garwboy on Twitter.

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