Clinical Depression and Statistical Physics

http://www.economist.com/science/displaystory.cfm?story_id=9861412

According to this paper published on Physical Review Letters, the wrist acceleration patterns over several days in healthy people vs. depressed people are different.

Nakamura et al. "Universal Scaling Law in Human Behavioral Organization" PRL 99, 138103 (2007) link here

Without doing the fancy math in the paper, you can tell who have depressive and non-dpressive patterns, because the healthy people sleep consistently, while the depressed people do not. I guess this was an unexpected finding, regardless of the scaling law.

The cumulative distributio of wating times of the activity bursts (that's a mouthful) follows a gamma distribution , and depressed people show a smaller gamma.

They claim that the smaller gamma could be a useful diagnostic tool, but the sleep pattern is good enough of a tool for me!