How Tanning Changes the Brain

Speculation on whether ultraviolet rays from tanning can become addictive has prompted a new study. It was shown that several parts of the brain that play a role in addiction were activated when exposed to ultraviolet rays. This could explain why so many people continue to tan despite the many associated health risks. What's more, frequent tanners met the criteria to be considered substance abusers based on answers to a survey.

http://well.blogs.nytimes.com/2011/08/12/how-tanning-changes-the-brain/