In short: A new study looks at the relationship between spider phobia and the size of the amygdala, a bit of the brain implicated in anxiety. The study found that those with spider phobia have a smaller left amygdala. Also the more serious your phobia the smaller your left amygdala. This was true only for phobia. They looked at disgust and general anxiety and they didn't find this link.
Research papers make great stories if you read them like I do. I tend to imagine how the study was actually done based on what the researchers describe in technical; distancing language. It was a trick I learned to make reading papers more fun. I have had so much practice that I can now do it as I go along. When I do this out loud people seem to enjoy it, so let me try.
There's this little place in Bern. It's on a narrow road lined with leafy trees. There's people walking about and riding bicycles all around the green grassy fields that surround the road. These same fields are covered with snow most of the winter, but today is sunny; not a cloud in the sky. The road leads to the psychiatric university hospital and in there is a door. The door says: Department of Psychiatric Neurophysiology. Behind the door you find Melanie Fisler, a blonde doctor in neuropsychology in her 30s. Melanie has and idea and goes to the end of the corridor to see her supervisor, Leila Soravia. She pitches Leila the following idea:
'Hey Leila, you know how people have looking at the amygdala and finding interesting stuff when they round up few medical and psychology students with anxiety and stick them in the functional MRI scanner? I bet you we could do the same in phobias... BUT we are going to buck the trend. Since everyone is obsessing with functional MRI that gives the pretty coloured pictures of what brain areas are activated and which ones are switched off, we'll take a look at the plain old MRI scan with the static images. Some people have done it but only a few.'
And Leila probably says 'Sounds good, go and do a literature search to make sure nobody's done this before and I'll go talk to my mates at the MRI department to see if I can sort us out some cheap scans. I'll offer them 6th author, see if that does the trick.'
So then they put up posters round the university, talk to all the clinicians that see patients directly they can find and they twist the arm of all of their students. When the dust settles they have about 24 people with spider phobia. Only 4 men, though.
'We might get criticised if we only have 4 men, we can't do any stats!' Melanie laments.
'Fear not,' Leila probably says, 'we'll just do the women, that way we'll save some scans anyway. Let's just round up 20 other women without phobia so we can compare the pictures'.
So they check that there was nothing else going on with the women and they and a lot of other people from the department give them a bunch of tests to check how scared of spiders they are, how anxious they are and how prone to disgust they are.
One other thing they check is that the women with phobia are able to look at a picture of a spider inside the scanner and keep still... I am not sure I would be able to do that myself!
Anyway, they get their scans from a nice chap called Roland Wiest that also helps them with measure the various brain bits and they discover that women with spider phobia have a smaller left amygdala than women without spider phobia. This is true even checking for anxiety in general and for disgust. (This last one surprised me as I thought that disgust would be closely linked with phobia).
One thing that must have really surprised Melanie is that the more scared the women were of spiders the smaller the left amygdala. You seldom find such clear link.
It was curious that the left amygdala, but not the right, was smaller. This might be because the left amygdala deals with scary things over time and the right one checks for anything, new or old, that might be a threat right here right now. What Melanie and her mates don't know is whether it is the phobia that shrinks the left amygdala or maybe a small left amygdala causes you to have a phobia.
I hope she goes back for more and gets to the bottom of this particular chicken-and-egg puzzle.
This work of fiction is loosely based on this scientific publication:
- Spider phobia is associated with decreased left amygdala volume: a cross-sectional study. Fisler et al. 2013