The work appears in the obscure Journal of Behavioural Decision Making, which is downright criminal. It deserves to be in the British Journal of Psychiatry ... and it's not often I think that about a paper.
In the first experiment, the authors quizzed people how many days per month they felt “depressed, sad, blue, tearful” or had “excessive anxiety about a number of events or activities.” They then asked them a series of questions designed to work out how they thought other people would answer than question. So they could work out where each individual thought they ranked within the general population, in terms of depression or anxiety symptoms.
Take a look. The top panel shows someone who felt depressed on 5 days a month, but believed this put him in the most depressed 70% of people. The second person felt depressed twice as often, but she thought she was below average.
That's just a correlation and doesn't prove causation, but in the second experiment, they randomly assigned people to get different versions of a survey which manipulated perceived rank, and they confirmed that rank was indeed associated with how "disabling" they felt a given level of symptoms would be.
Now, this is just common sense, in a way. Of course whether you think of yourself as abnormal will depend on what you think of as normal - that's what "abnormal" means. We understand ourselves in the context of other people.
But this common sense is maybe not so common nowadays; you can read a hundred papers about the chemistry, genetics or causes of "depression" without a consideration of what "depression" (i.e. "abnormal" as opposed to "normal" mood) is.
The implications are big. Here's my main concern. Right now a lot of people think that promoting the idea that mental illness is very common is a good idea. Their stated goal is that by 'normalizing' mental illness, we'll destigmatize it. This will both help the mentally ill to cope, and encourage people to talk about their own mental health and get help.
All very nice. I've accused such campaigns of being based on dodgy stats, but this paper suggests that such campaigns could end up having exactly the opposite effect from that intended - they could lead to under-diagnosis, and increased stigma.
Suppose being depressed or anxious becomes seen as more 'normal'. According to these data, this will make people who are depressed or anxious less likely to seek help, for any given level of symptoms. Change people's perceptions of other people, and you'll change how they see themselves.
Worse, normalizing distress could - paradoxically - make those who do seek help seem more abnormal. Think about it: if depression and anxiety are normal, surely only an abnormal person would need special help to deal with them.
It's a small step from this to the idea that mental illness is mere personal weakness, laziness, attention-seeking, or scrounging. 'What's your problem? Everyone feels down or worried sometimes... most of us just deal with it.' If everyone is mentally ill, then no-one is really mentally ill... so the "mentally ill" must have something else wrong with them. Not very nice.
I'm not sure if this has happened, or will ever happen, but it's something to think about.
Melrose, K., Brown, G., and Wood, A. (2012). Am I Abnormal? Relative Rank and Social Norm Effects in Judgments of Anxiety and Depression Symptom Severity Journal of Behavioral Decision Making DOI: 10.1002/bdm.1754