Scientists May Have Found Humankind's Original Addiction

In studying how ultraviolet radiation affects skin, scientists may have stumbled across humankind's original addiction: sunlight.

A new study in the journal Cell shows that UV radiation, even in modest amounts, prompts production of the "feel-good" hormone beta-endorphin that numbs mice to pain. When scientists blocked beta-endorphin with the drug Naloxone (used to combat heroin overdoses in hospital emergency rooms), UV-exposed mice experienced withdrawal symptoms: shaking, teeth-chattering and jumpiness.

It's the first time scientists have thoroughly mapped out the pathway in mice from UV exposure, to rising beta-endorphin levels in the blood, to physical dependence on sunlight. The findings add to a field of research that examines extreme tanning as a possible addiction in humans, and could explain why people love to sunbathe -- even though it's clear that UV rays damage skin cells, age skin prematurely and cause skin cancer.

In addition, the findings could pave the way for more research on battling opiate addiction in general, since beta-endorphins are opioids -- our body's own natural version of opiate-like drugs.

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