Former New York City Mayor Michael Bloomberg has sharply criticized Colorado’s decision to legalize marijuana and called it a terrible idea.

Bloomberg said at a meeting at the Aspen Institute on Friday that marijuana is hurting the developing minds of children. He admitted to smoking a joint in the 1960s, but he said the drug is stronger, more accessible and more damaging today.

He says using marijuana could reduce the IQ of students and he said it’s different than using alcohol.

Amendment 64 was approved by Colorado voters in 2012 and allows recreational marijuana for adults over 21. In 2000, 54 percent of Colorado voters approved Amendment 20, which amended Colorado’s state constitution to allow the medical use of marijuana.

(AP)