The Japanese Society for Clinical Toxicology examined statistics on patients who were admitted for caffeine poisoning at 38 hospitals with emergency departments in the five years from fiscal 2011, reports The Asahi Shimbum.

The study was prompted after a series of acute caffeine poisoning cases were reported, including a fatal overdose in 2015 in the southern island of Kyushu. A man in his 20s, who worked overnight shifts, died after consuming both caffeine pills and energy drinks.