Health effects unclear for 4/20 celebrations

Popular explanations for the origin of 420:

Adolf Hitler died April 20

Many say tea time in Holland, The Netherlands - where marijuana is legal - is 4:20 p.m..

Many say 420 is a police dispatch code for marijuana smoking in progress.

Jerry Garcia, former lead singer of the Grateful Dead, died at about 4:20 p.m.

Students at San Rafael High School, in California, would meet at 4:20 p.m. to smoke marijuana and adopted 420 to use as a code.