I've long prided myself as someone barely affected by jet lag, likely because of my never sticking to any regular sleep schedule. For this reason, I've generally not been affected by daylight saving time (DST), but this spring, I believe I've been negatively affected by the DST switch. I've had a cold during the last week, and it seems like the timezone change made my sleep worse. Of course, I might be imagining this, and perhaps my reduced sleep quality is due to my being sick.
However, I'm not alone. There are studies that show that the clock shift can have adverse effects on health, by increasing the risk of heart attacks and disrupting the circadian rhythm. Things are never black-and-white, though, and there are other studies that claim that the increased afternoon sunlight causes more outdoor exercise.