Is OCD caused by a bias in the brain?

We need to try to understand what’s going on inside the brain to bring on these obsessions in OCD. Trevor Robbins is a professor of cognitive neuroscience at the University of Cambridge…

Trevor - The classical idea would be, intrusive thoughts are often very unpleasant and cause anxiety. In order to cope with this anxiety and reduce the stress, you perform this repetitive behaviour. It's a kind of a coping response. And there may be some truth to that, but the evidence isn't totally clear. It's interesting from a psychological point of view that we know that avoidance behaviour, for example, in the lab, often develops into what we call habits. Habits are more automatic and they no longer really depend on the original conditions which produce them. In other words, you might perform the behaviour initially to reduce anxiety, but then you just do it automatically and the anxiety is irrelevant then in the brain. There's a balance between your goal directed behaviour and habits. We think it's flipped over a bit to the habit system in OCD. That's partly why it becomes more automatic and less amenable to cognitive manipulation as it were.

James - Fascinating to hear the nuance and the active debate clearly on this particular condition. If we stick with the classical model for one minute, what's the psychological sequence of thoughts that leads some people to demonstrate the behaviours, the compulsions that we see? Because I think there's quite a few misconceptions on that topic.

Trevor - There's a lot, and OCD is expressed in a variety of ways, but the classical example really is germs: fear of infection. This leads to excessive hygienic behaviours, washing your hands so often with bleach that you actually cause damage. Then clearly it's a compulsive behaviour. Another classic example really is checking. Checking whether you've locked the door after you've left your house, maybe spending 15 or 20 minutes to ameliorate this anxiety that somehow your house is going to be violated in some way. Checking by the way is a very fundamental symptom in OCD. Even if you are afraid of germs, essentially you are checking all the time whether your skin is clean. OCD can often extend into other areas, for example, perfectionism and ordering, which is a more cognitive aspect. But again, checking is important there. Checking that the arrangement is perfect, checking uncertainty. Uncertainty is core to OCD. The issue I suppose is whether uncertainty causes inappropriate anxiety which is relieved in some way.

James - And these compulsions, they have, on the face of it, a practical and reasonable reason for doing something. Checking, for example, that you haven't left the oven on, that makes sense as something to do.

Trevor - Absolutely. In a sense, habits are obviously very adaptive and leading them into compulsive behaviour is also adaptive in some sense. As a scientist, I'm fairly careful and compulsive and checking, if you are proofreading for example, that's a skill that you have to develop, being very careful and checking everything is correct. In a sense, we all have a bit of OCD and what I would argue is that there is a dimension of behaviour called compulsivity which extends in very normal areas. For example, stamp collecting or something like that. But then gradually it becomes excessive and there is a point where this tendency to compulsivity is maladaptive because it stops you doing other things, for example, or you are not even doing the thing you wanted to do in the most efficient manner. It's really interfering with your life because you're spending all your time doing this behaviour.

James - It's interesting because one of the key frustrations I find having spoken to people with quite debilitating OCD is people describing themselves as a bit OCD because they like to keep their room tidy or because they engage in other sorts of behaviours. So I was interested to pick up on that.

Trevor - It's a major problem I think socially because OCD is stigmatised and that I think that has prevented large attention being devoted to it for treatments and so forth and research activities. This has to change because it's a very serious and disabling disorder in quite a large number of people. The incidence is 2 to 3% of the general population, which is enormous.

James - That's the kind of psychological grounding. This is manifesting in a wide variety of ways as we've described, presumably with a common neurological basis.

Trevor - Yes, indeed. I said earlier, one way of thinking about this is a bias towards the habit system in the brain from the goal directed system. There's a lot of brain scanning experiments in humans and experimental animals showing this dissociation between the systems. You can discern some of this in OCD patients, but I think there's a third factor. The third factor relates to the system which controls the balance between these systems in the frontal lobes of the brain, in the frontal cortex. We call this the arbitration system, and it's mediated by parts of the frontal cortex and the stratum, which seem to switch in whichever behavioural system is required. If this switch is a bit inefficient, then you're going to land up with habits. Compulsions aren't simply habits, they're habits which can't be regulated, which you can't inhibit. OCD patients also are a bit rigid cognitively. They're cognitively inflexible if you like. So that doesn't help either.

James - A lot of people who experience OCD will point to trauma earlier on in their life. Can you elucidate the detail as to why that might be related and where that fits in the psychology or the neurology as you've described it?

Trevor - That's a very interesting one. Trauma obviously is associated with stress. Really it comes back to what I was saying earlier that maybe you have to cope with that stress. You have to protect the brain, you feel anxiety as a consequence of the stress and you indulge in these compulsive behaviours in order to reduce the stress. That's the hypothesis. On the other hand, the other possibility is that something in brain development just goes slightly wrong and you find yourself repeating your behaviours. One idea we've had is that when that happens to you, that makes you anxious as well because you have to find reasons to explain why you're doing this weird behaviour.