There are, for instance, more heart attacks and digestive and immune-related diseases in the week following the shift to DST. A small bump in car accidents also tends to be recorded.
Long-term health effects include depression, slowed metabolism, weight gain and cluster headaches.
That's because our "social clock", ie, the schedule under which our societies operate, and our internal clocks, which are more or less aligned with the sun, are out of whack.