But there is something of a debate as to WHY that is. Is it because people who are depressed take less good care of themselves? Of their health? Is depression related to physiological changes that slow down the healing process in people who are ill? Is depression actually just the conscious expression of inflammatory dysregulation in some of us? An epiphenomenon of a cardiovascular problem, if you will?
We are trying to figure all this out.
But I would like to take a moment to question why we are asking what we are asking. After all, does it matter WHY depression leads to worsened health outcomes, so long as we know that it does?
Does it matter whether depression causes cardiovascular disease, or is it enough to know that the two are associated? Correlated. Tend to happen together. A lot.
Nobody believes what psychologists say anymore. We are the scientific version of the boy who cried wolf. We try to be helpful. We say things like "people with dogs are happier" and then (logically) we figure that giving unhappy people dogs will make them happier too! It's not dumb. It's cute.
Avoiding those kinds of fallacies in our field really is pretty difficult. Especially when you're torn between being a science that wants to stay pure and being a science that wants to help. Because if you want to help, then you really need to know HOW to help. And to know how to help, you need to know WHY good things happen in some cases and bad things happen in others.
If only we weren't so bad at that...
However. Hope is not lost. We are very good at knowing which sorts of things tend to happen together. For example, depression and CVD. They happen together. Self-esteem and success. Social support and well-being. Exercise and morale. Yes, let's use exercise and morale as an example.
In this excellent paper the authors show that: "Regular exercise is associated with reduced anxious and depressive symptoms in the population at large, but the association is not because of causal effects of exercise" (p.897).
Does that mean that you shouldn't bother exercising? Of course not. But it DOES mean that if you have been depressed and anxious, once you start exercising, you are likely to be feeling better.
The problem is: so what? So we can't prescribe exercise to make people feel better (there is plenty of disagreement with this viewpoint, by the way), and we are left completely thwarted in our goal of being helpful.
Harumph.
Harumph.
But. Let's say we were to bypass the entire problem of causation. Let's say we were to get really crazy and say that we just weren't going to BUY IN to the whole IDEA of causation. (Take that, Liebnitz.) And just as an aside, we wouldn't be the first. Remember Hume:
"Thus we remember to have seen that species of object we call flame, and to have felt that species of sensation we call heat. We likewise call to mind their constant conjunction in all past instances. Without any farther ceremony, we call the one cause and the other effect, and infer the existence of the one from that of the other." -- A Treatise of Human Nature (taken from this very excellent slide show)But what we do know is that the two tend to happen together. Associationism.
So you should exercise because people who exercise feel good. And you should feel good because who feel good exercise.
And if you feel like crap, exercise isn't going to change that.
But if you want to change that, exercise might be something to look into.
I believe that one of the reasons associationism as a philosophy hasn't been embraced by scientific psychology is that it's more mind-boggling than causation. However, I believe that in certain cases, getting stuck on the question of causality in health is counter-productive. It is not helpful.
Perhaps if we identify the sorts of healthy behaviors and physiological states we find optimal, and learn how they cluster together, we will be able to DESCRIBE the kinds of healthy states we would like to move towards. Then we can tackle the question of causality.
Indeed, if we assume that the natural state of the organism is to move towards health -- and there is evidence to suggest that it is -- then perhaps simply presenting people with healthy alternatives will move them towards health, less by cause than by osmosis.
