A study finds that mice (regularly) exposed to UV produced the feel-good opioid β-endorphin, and behaved like addicts.

What’s more, when they were given a drug that blocked the opioid effects, they went through the rodent equivalent of withdrawal: shaky paws and (chattering) teeth. The study is in the journal Cell. [Gillian L. Fell et al, Skin β-Endorphin Mediates Addiction to UV Light] (To hear an interview with study author David E. Fisher, go to the Cell website.)

The mice were exposed to UV light roughly on par with a fair-skinned human soaking up a half-hour of Florida (midday) sun, five days a week for a month-and-a-half. But it took just one week for the endorphin levels to zoom.

Mice are normally nocturnal and, of course, covered by fur. But the research team says that the apparent physical reward for UV (exposure) suggests it’s worth exploring if a similar chemical reaction may be spurring humans to keep running to the beach or tanning bed.

They also say it’s likely sunblock would protect against these UV-induced addictive behaviors. Yet another reason to slather on the (sunscreen).