This article in Scientic American hints at some potential health-related impacts of blogging (all positive by the way). According to the article:
expressive writing produces many physiological benefits. Research shows that it improves memory and sleep, boosts immune cell activity and reduces viral load in AIDS patients, and even speeds healing after surgery.
Now, I'm not certain how "expressive" an article about VBA and VSTO can be... so it may not be helping me much at all, but it may help YOU to sleep.
Of course it may be possible to take a contrary view and suggest that people actually blog because they are ill. The article in describing the physiology of the brain related to writing suggest that the temporal lobes (which govern speech) may be involved as well. Then as proof cites Wernicke's aphasia which appears to be rooted in the temporal lobes:
People with Wernicke’s aphasia speak in gibberish and often write constantly. In light of these traits, Flaherty speculates that some activity in this area could foster the urge to blog.
Uh huh, gibberish, constant writing, bloggers... all cut from the same cloth.
