In the lyrics to the song "Dumb," Kurt Cobain sang "I think I'm dumb, or maybe just happy." Like many people battling serious depression, Cobain seems to have thought that being happy required being oblivious to the many depressing truths in the world.
Depression has a bad habit of screwing up your perceptions, but in this case, Cobain's belief at least appears to have some science behind it. Psychologists talk about depressive realism, the idea that depressed people have removed the rose-colored glasses everyone else wears. If they look at the world and see bad things everywhere, it's because the world is an ugly place.
In other words, people with depression are not pessimists, they are realists.
I don't think it's true.
Granted, we all have illusions, and some of them are positive. But some are negative too. And depressed people are just plain pessimistic across the board. If you only consider positive illusions, then, sure, depressed people are more accurate than normals, but that's only because they are more pessimistic about everything.
Let me illustrate the difference. Most people think they are above-average drivers. If a depressed person accurately classifies herself as average, is she accurate or does her pessimism cancel out her optimism? When you only look at positive illusions (like above average driving), there's no way to know. And since the classic literature on depressive realism grew out of the study of positive illusions, the first round of results made it seem like depressed people are just plain more accurate.
But what happens when we look at negative illusions? To take a trivial example, most people think they have a below-average sense of smell; we guess we will not be as good at identifying odors as everyone else. If the depressive realism idea is true, then depressed people should be more optimistic than the rest of us, but if depressive pessimism is true, they should be even more pessimistic. No one has ever tested this idea, but much newer research suggests depressed people will be more pessimistic. And it's one thing when it applies to our sense of smell; it's another when it applies to our opinions on what other people think about us, whether the future holds promise, and whether we are good people. That kind of pessimism can make you want to start a grunge band.
The reason this is important is that depression is as common as it is devastating. Lifetime prevalence of major depressive disorder in the US is around 20 percent, and is undertreated. And yet, there are very good treatments out there. The idea of depressive realism gives depressed people an excuse to skip treatment. When you believe in depressive realism, then who wants to be cured? Therapy seems like brainwashing, antidepressants look like numbing agents, and psychiatrists look like liars.
Even worse, the idea of depressive realism makes more sense to when you are depressed. Depression doesn't just make you pessimistic, it makes pessimism feel like realism. It takes over your brain. It makes it hard to see your own depression.
The debate over depressive realism isn't resolved. It's being worked out by scientists right now. But my money is on it being wrong. Cognitive therapy, one of the most effective treatments for depression, doesn't teach you to believe lies. It teaches you (among other things) to challenge your negative thoughts with frequent reality testing. Patients are encouraged to frequently check their thoughts against objectively measurable reality. And reality turns out to be an extremely powerful antidote to depression.