Since the subject of health risks is in the news....
The main health effects of DST that I know of are the following.
* Extra afternoon daylight may encourage people to exercise more,
which should be a big win.
* Sunlight triggers vitamin D synthesis, but overexposure leads to
skin cancer; so whether DST helps or hurts here depends on your
latitude and daily schedule.
* DST may be helpful in fighting some forms of depression:
Henry Olders (2003-08-13). "Average sunrise time predicts
depression prevalence". Journal of Psychosomatic Research 55
(2): 99-105. DOI:10.1016/S0022-3999(02)00479-8.
Some argue the reverse, though.
* DST can help night-blindness sufferers, though it can also hurt:
it depends on their schedule.
* DST's clock-changes temporarily disrupt the sleep cycle, which can
lead to suboptimal decisions (e.g., while driving, or while trading
stocks). There have been several studies of these secondary
effects, but I know of no studies of any direct health risks.
So the vast majority of this stuff is speculative and/or anecdotal;
there's only one scientific study that I know of.
