Why Scientists Still Can’t Determine What Happens To Our Brains When We’re Depressed
Scientists are trying to determine what happens to our brains when we’re depressed but a lack of communication between them isn’t helping.
As researchers look into the history of depression, they also struggle to replicate the human brain to help diagnose the disease for similar reasons.
On a recent episode of Think, Krys Boyd spoke with journalist Simon Lewsen about what happens to our brains when we’re depressed — and why scientists haven’t figured it out yet. The two also spoke about neuroscientist Sean Hill, who runs Toronto's Krembil Centre for Neuroinformatics, and why he was bothered by the lack of communication between scientists.
This interview has been lightly edited for length and clarity. Listen to the full episode.
On why neuroscientist Sean Hill was bothered by the lack of communication between scientists
It was this demoralizing experience for Hill, because he realized how much work it takes to generate information about the brain. He was trying to understand how cat brains respond to noise. It felt to him like, God, if we're all working so hard to generate this data, and if cats have to sacrifice their lives to generate this data, it should be put to the most possible use. It should live in the public domain. People should use it again and again and again, and that made him feel like something was wrong in the way we practice science. It made him very convinced that we have to think differently about how we do science and how we share the data that we work so hard to generate.
On the causes of depression and what takes place in our brains
We're not completely in the dark here. We do know that we have high-level ideas as to which brain regions play a role in regulating mood. We have a sense that the neurotransmitter serotonin, the brain chemical, plays a role in regulating mood. We have some sense as to what happens in a depressed blood brain, but we really don't know a lot. That's kind of a big problem. We don't even really know enough to distinguish between different subtypes of depression.
Depression is perhaps better thought of as a symptom of a variety of different diseases. This might explain why we have trouble treating depression because it's simply possible that we are treating different conditions that we've just happened to label with the same name.
On the current treatments for depression and their effective rates
The current class of antidepressants work for somewhere between 40 to 60% of people. So I mean, that's better than nothing. And it’s great to have those drugs out there.
But there are a few things missing here. One of the things we're missing is we don't really know what's going on. So we've tested people with those drugs against placebos. We've seen some, quite compelling evidence that those drugs to some degree work. But we don't know, on a molecular biological level in detail, exactly how they work or why they work.
The other thing we're missing is that 40%. If SSRIs are effective for between 40% - 60% of people with depression, then there's at least 40% of people for whom SSRIs are not effective. And we don't know why that is. But one possible explanation is that the biological mechanisms behind their depression is different. And, you know, we're treating bronchitis when we could be treating heart disease.
On how neuroscientists can replicate the human brain
There were huge debates within the realm of neuroscience as to how best to build a model, a computerized model of a brain. There's a recognition among pretty much everyone that models a brain, that those models are abstractions of some kind. You are using the best available knowledge to try and simulate some kind of brain process, not because you think that simulation is perfect, but just because you think it's the best you've got.
So you're building computer algorithms that simulate some kind of component of the brain. And then you test that simulation and see if those tests are actually replicated out in the real world. I don't think anybody really expects that we will ever create a perfect full scale model of the human brain.
On the disconnect between neuroscience and psychiatry
Hill feels that there's a sort of profound disconnect there, that he feels that psychiatrists aren't thinking a whole lot about brain biology. For him, it speaks more to a failure of neuroscience, that neuroscientists haven't given psychiatrists enough information at this point to work with. So if you're a psychiatrist, fundamentally, your goal is to treat the patient in front of you and to make them feel better. That doesn't involve a whole lot of neuroscientific thinking because neuroscience doesn't have a whole lot of answers about what's happening within the brain when a person is depressed.
The goal should be to try and ascertain what the underlying biological conditions are for this person to try and find the underlying disease, which is something that psychiatrists really aren't doing because it's not clear how they would do that. We don't know enough of the brain for them to do that. But we'd like to get to a point where psychiatrists can do that and do that model.
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