Interest in electrode therapy and psychedelics for OCD

Once patients do get over the critical hurdle of diagnosis, effective treatments are out there, but it’s something of a mixed picture, hardly surprising given the evolving theories as to what the mechanism behind the condition actually is. Here to talk us through what we do know is Camilla Nord, who leads the mental health neuroscience programme of research at the MRC Cognition and Brain Sciences Unit at the University of Cambridge. We started with the gold standard first-line treatment or OCD, cognitive behavioural therapy…

Camilla - In the context of OCD, cognitive behavioral therapy or CBT is a kind of talk therapy, but it's a little bit different than the way you might think about talk therapies. It's not dealing with your history and your family and where these things might come from. It's dealing with symptoms often in the here and now is how you can think about it. One aspect of CBT is the C - cognitions - that you experience. There you might work on why you have certain thoughts that emerge and perhaps reexamine, or it's called restructuring, those thoughts. Then particularly crucial in OCD treatment is the B part, the behaviours. Even if you don't experience compulsions as some people with OCD don't, actually, the behavioural part of CBT is really crucial because this often involves exposing you to the very things that you're having intrusive thoughts about. Working on those reactions often little by little, starting with something at the minor end of what you're having intrusive thoughts about and working up to maybe a more realistic setting of what you experienced day to day.

James - Say your obsession was over germs and health. By exposing you to unhygienic scenarios and the result being that you are okay, you overcome the fear of the germs and realise that no significant harm came to you.

Camilla - Yes, exactly. So if you're particularly worried, for example, about germs on something that you're about to eat, you might work your way towards eating it, starting with maybe handling it and observing, experiencing that you don't become sick, you don't have consequences from that. I think I remember one context of a therapist not washing their hands after the loo and then touching a biscuit. We can all imagine how that might be a bit gross, but for someone with OCD that is a prohibitive, intrusive thought that they might have and that might lead to the kind of compulsions that they experience. And so working up to maybe even being able to eat that biscuit.

James - Well, let's hope for their sake that it is effective. But as I understand it, CBT works for 75% of people. So that still leaves a significant portion who persist with their symptoms even after cognitive behavioural therapy.

Camilla - Yeah. And I should say that's 75% for whom it works a little bit. So they have a response to it, which would mean a noticeable reduction in your symptoms. But even in that 75%, there will be a substantial number of people who have some residual symptoms. It doesn't necessarily make them totally go away.

James - Okay. And on top of that, is the point that the waiting list to see a psychiatrist is very long.

Camilla - That presents a challenge because for that 25% who don't experience really any noticeable change in their symptoms, there are other strategies that exist, but they might be difficult to access. For example, some people respond very well to the high dose of antidepressants, the most common class of antidepressants called selective serotonin reuptake inhibitors or SSRIs. But with that, you would want to be working with a medical doctor to work out the right dose for you, ensuring that you don't have side effects and so on. Sometimes those can be used in combination with CBT and it actually helps you access the CBT to have that pharmacological intervention. It achieves the goals of the psychotherapy that it might not achieve on its own.

James - As we've been hearing, there's an active debate as to what the mechanism of the disease actually is or the condition actually is. Is OCD caused by a chemical imbalance in the brain, perhaps? And that would make sense as to why SSRIs would be effective. Or perhaps it's a bias towards a certain brain network, the habit network and against the goal directed system. Because depending on that answer to the question of what the mechanism is, the treatments might be different?

Camilla - I'm not sure that I agree that the treatments would be different depending on whether you think of it as a chemical imbalance or not. I don't think of OCD as a chemical imbalance. I think many neuroscientists don't. Brain networks, it might not even be exactly the same change in every patient. Nevertheless, we use lots of drugs for things that aren't just a deficit in that problem. Paracetamol works without you having to have a deficit in the specific thing that paracetamol is targeting. I think SSRIs have properties that can change brain networks, and so it's sensible that they might be working in OCD without necessarily curing some sort of decrease in a brain chemical.

James - Tell me about the interest in deep brain stimulation at the moment and its potential perhaps in curing OCD or alleviating the symptoms.

Camilla - Deep brain stimulation is a treatment that originally comes from Parkinson's disease. The way that it works is, surgically, neurosurgeons implant electrodes deep in the brain, in the structures that we know to be involved in OCD. Then by delivering electrical currents to those regions, it can change the biasing of brain networks in a direction closer to people without OCD. Whether or not it works in OCD was something that has now been explored in a couple of big studies and there does seem to be effectiveness, but I think the problem, or I suppose the challenge with deep brain stimulation is you have to get the target right. There we get back to the idea of, does everyone necessarily have the same region that should be targeted overall? These are patients who don't respond to anything else. This intervention works in, I think, more than half of them, over 60%. So that is still a really useful and effective treatment. But I would say that, in the long run, for most patients with OCD, they might not be candidates for something as risky as neurosurgery, but there might be other ways of changing those brain networks, for example, with non-invasive brain stimulation.

James - Quite. And to go one step further, what about something like a psychedelic treatment? I know there's obviously lots of interest in psilocybin and ketamine for treatment resistant depression, the theory being that they encourage the growth of connections between systems in the brain. So why couldn't the same be true for OCD potentially?

Camilla - Yeah, you're right. The interesting thing about ketamine is, in OCD, like in depression, SSRIs take a really long time to work, and yet ketamine in depression is a rapid acting antidepressant. So it's very effective for many patients and it works quite quickly. That would be incredibly useful for people with OCD to have more immediate relief from these very debilitating symptoms. In many cases, the jury is still out. I think there is probably a little bit more work that's been done now on ketamine than on, say psilocybin, which I think is truly ongoing, because you really need things like a robust placebo group working at the level of, is it this specific, or is it your expectations of getting better, which are incredibly powerful unconscious drivers of treatment response in many cases.