Depressed people often think intensely about their problems. These thoughts are called ruminations; they are persistent and depressed people have difficulty thinking about anything else. Numerous studies have also shown that this thinking style is often highly analytical. They dwell on a complex problem, breaking it down into smaller components, which are considered one at a time.
The author suggests that a depressive mindstate is one that is also useful for solving complex problems. In fact, the loss of interest in sex, eating, and social activities could be a method of reducing distractions, further promoting analysis. It got me wondering, could the same thing be true of the "religious mindset"?
Now hear me out.
Religion encourages the removal of many distractions, the awfully named "Sins of the Flesh" (always thought that should refer to cannibalism). It provides structure to the day, reducing the need for thought about daily schedules, what to wear, etc. There's a popular story (probably an urban legend) that Einstein did a similar thing, buying many sets of the identical wardrobe so he didn't have to waste time deciding what to wear.
Religion encourages temperance and moderation, meaning adherents would tend to (hypothetically) avoid issue like alcoholism, obesity, and anorexia, while having mandatory rest & relaxation breaks built into the schedule.
It also encourages a quiet, contemplative, introspective state for prayer and study. This "prayer state", like depression, could potentially be advantageous for analysis of complex problems.
I'm not being entirely serious with this, but it's a fun parallel, and it would be interesting to see someone do research on this.