Is Indoor Tanning Habit Forming?   Over a million people visit tanning salons each day in the U.S.  Many enthusiasts comment that indoor tanning helps them feel relaxed. These investigators sought to determine whether a physiologically reinforcing effect of UV exposure encourages tanning behavior. Fourteen regular indoor tanners were enrolled (13 female; age range, 22-34 years). Every Monday and Wednesday for six weeks, the participants were directed to successive use of two seemingly identical tanning booths. One booth delivered UV radiation, and the other did not; the booths were otherwise identical (e.g., both emitted visible light and heat). On Fridays, participants were free to choose either booth for a tanning session. Participants filled out questionnaires addressing their subjective experience after each tanning session. When given the choice, participants selected the booth that delivered UV radiation 95% of the time. In addition, they reported greater relaxation scores and lower tension scores after UV exposure than after non-UV exposure.  The results suggest that chronic indoor tanners had the ability to detect which booth delivered UV radiation and which did not, despite multiple levels of blinding. The authors postulate that UV-induced endorphin production may mediate the feeling of relaxation associated with indoor tanning.   COMMENT: This well-designed study shows that the determinants of indoor tanning behavior go beyond the desire for a tanned appearance. UV radiation delivered by tanning booths may be habit forming, and it may be as complex a challenge to cease indoor tanning as it is to abandon other addictive behaviors, such as smoking. - Mary Wu Chang, MD Feldman SR et al. Ultraviolet exposure is a reinforcing stimulus in frequent indoor tanners.  Journal of the Academy of Dermatology,  2004 July; 51:45-51.