How do you simulate anxiety?
Most of us will have felt anxious at some point in life, but for people with an anxiety disorder, it’s more constant, affecting daily activities, and can be very difficult to control. Anxiety can include physiological symptoms - changes in heart rate or breathing for instance, cognitive symptoms - feeling unable to think clearly - and emotional symptoms. But exactly how these relate to each other isn’t clear. In order to unpick these relationships, Cambridge University scientists simulated a state of physiological anxiety in participants to see how and if the other symptoms manifest. Cognitive neuroscientist Duncan Astle - who wasn’t an author on the study - told Katie Haylor about it...
Duncan - So they recruited healthy, typically developing adults, who had no history of anxiety and they had them breathe one of two different types of air. So one is just standard air and the other has 7 1/2 percent extra CO2 in it. And they found that when the people were breathing the enriched CO2 air, their bodies entered a state of physiological anxiety. So for example their heart rate would increase, their blood pressure would increase. They used various different types of questionnaire and the people reported that they felt more panicked.
Katie - Why would adding more carbon dioxide to the air someone breaths change that physiological state?
Duncan - Well one argument is that the body might have some kind of in-built mechanism that when it senses its oxygen levels dropping slightly, it produces a physiological anxiety effect in order to try and get the person to correct that. So for example to get out, to get more oxygen etc.. So it's a way of piggybacking on that presumably quite kind of basic mechanism to induce the experience of anxiety.
Katie - OK, so you've got a bunch of people who aren't anxious and you've simulated anxiety by changing the air that they breathe. How does this relate then to how you feel or how you might think?
Duncan - So whilst people were in this state they had them perform multiple different tasks and actually across multiple experiments. They firstly had subjects perform a task that requires them to switch between sorting shapes by different rules, and that sounds like quite an arbitrary thing but it actually gets really tricky.
If anyone’s ever played something like Snap or Uno, when you have to switch between different rules, say between colour and shape for example and you might find you make a lot of mistakes like you start to sort by the wrong rule. This task has been used a lot by cognitive psychologists because it's thought to really tax what we call executive functions that are heavily dependent on the frontal lobes.
And they found that subjects got very significantly worse when they were in this state of anxiety and the degree to which they got worse was directly related to the degree to which they were experiencing the anxiety.
Katie - Is this what you would expect to see in someone who, you're not simulating anxiety, they’re genuinely anxious, this same kind of impairment of executive function?
Duncan - So people who experience anxiety naturally, do report that exact same thing. The challenge is of course that when you study someone who's experiencing anxiety naturally, there might be all sorts of other things going on. And so knowing that it's the physiological impact of their anxiety that's directly related to their cognition is really tricky. Whereas in this case, we can know that because that's the only thing that they've manipulated.
And then in another experiment they had them do a simple spatial short term memory task, and they found that they got significantly worse at that also. So it's really compelling evidence that if you mimic the physiological effects of being highly anxious then it will have a big impact upon your higher order cognitive skills.
Katie - And where does the third component come into this? Mood?
Duncan - Using lots of questionnaires, they found that there was a shift towards negative affect. So they showed them for instance faces with different emotions and words with different emotional content. And they found that subjects became more negatively biased as a result of the CO2 enrichment.
Katie - I'm not sure I would have wanted to be one of these volunteers! Does this hint at anything around how we try and help people who are anxious? I guess there's the long term methods that we might use, but also in the short term you might be advised to focus on your breathing for instance.
Duncan - For a long time we've known for instance things like physical exercise are really good in the long term for conditions like anxiety and depression. One reason why that might be, is because it has a direct impact upon your physiology and may make you better able to regulate your own physiological responses. And also a lot of techniques that we think of as being helpful for people who are experiencing anxiety, like breathing techniques, may have a direct because ultimately it's the physiological signs of being anxious that have the most direct impact on things like cognition.
What these authors have managed to show is that you can experimentally create the experience of being anxious in a relatively realistic way and that does mimic lots of the symptoms that we know do come with anxiety. And that then opens the door to a whole series of experiments including interventions to see whether you can try and mitigate that physiological effect. And that's the kind of work that's very hard to do without some sort experimental model of being anxious which is what this creates.