In 1968, researchers from the Royal College of General Practitioners began tracking approximately 46,000 women in the United Kingdom — half of whom actively used the birth control pill and half of whom had never used it. Follow-up reports on the study, one of the world’s largest continuing explorations into the health effects of hormonal contraception, suggested that pill users have a significantly lower rate of death from cancers and other diseases but a higher rate of death from something surprising: violence.
The longer they’d been on the pill, the more likely this fate became; those who’d been on the pill for more than eight years had an increased risk of 116 percent. It’s a small finding, but significant enough that chance couldn’t explain it.