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.