Like sugar and drugs, UV radiation activates reward centers in the brains of habitual tanners. One study even found that, in rats, UV functions much like heroin: It produces feel-good endorphins, increases pain thresholds—and, later, elicits withdrawal symptoms. And lest you think tanning is less dangerous than drugs, we’ve got just one word for you: melanoma.

READ MORE: The Truth About Tanning Addiction