Today, the original purpose of daylight saving time — maximizing the amount of light during waking hours —still holds true. But more studies are popping up suggesting that people who are already susceptible to certain health problems, such as high blood pressure and depression, will feel the effects even more when the clocks move forward.
A Swedish study published in the New England Journal of Medicine in 2008 found the risk of a heart attack increases in the days right after the daylight saving time change.
via How to survive the daylight saving time switch – Calgary – CBC News.