05 October 2007

No one's depressed when doing a polka

Should I be concerned that I spend two or three hours at a time perfectly still, then move for a moment or two before going back to stasis? Glad there's a power law governing the way I move. "In this week's Physical Review Letters, Yoshiharu Yamamoto of the University of Tokyo and his colleagues explain how the movements of people suffering from clinical depression can be described by a power law—and how this law is so different from that of healthy people that it looks truly diagnostic."

The curves produced by plotting the lengths of low-activity periods against their frequency were strikingly different in healthy and depressed people. This reflects not inactivity by the depressed (though they were, indeed, less active) but a difference in the way that the healthy and the depressed spread their resting periods over the day. Depressed people experience longer resting periods more frequently and shorter ones less frequently than healthy people do.
So...if this is correct than what would happen flipping this on its head? Let's assume for a moment that the depression and movement curves are merely correlated. Is it a one-way street, or is it a feedback loop that can be affected by changing resting periods. Suppose a therapy, the sole purpose of which is to force the patient to move/rest in accordance with the "healthy" power law curve. Would that be efficacious?

Or, there is a purely causal relationship, in which case the altered movement curve is solely useful for objective diagnosis. If that's the case, it's at least a huge leap forward in diagnosis.

Personally, I don't believe in many purely causal relationships in biology. The systems are so complex that the interactions tend to feedback, either directly or through related channels. Given that, I hope someone takes this research in hand and tries studying the effects of my proposed treatment.

Here's a link to the paper.

Also, via MindHacks