Tanning may be an addictive practice that is rooted in the release of pain-dulling endorphines, reports a study by researcher David Fisher of Massachusetts General Hospital and Harvard Medical School.
Skin cancer is the most common form of cancer in the U.S., and tanning greatly increases the risk of developing the dangerous and often life-threatening disease. But despite widespread awareness about the reality of sun soaking and skin cancer, tanners - at salons and under the sun - can't seem to break the habit, particularly in the summer.
One theory about why this may be the case has to do with exposure to UV light, which boosts the production of endorphins that relieve pain by activating opioid receptors. Endorphins use the same pathway as opioid drugs such as morphine and heroin and many tanners fit the clinical criteria for a substance-related disorder, so exploring a possible addiction scenario made sense.
To examine this addiction theory, researchers tested whether mice exposed to UV light for six weeks would register an increase in endorphin levels in their blood. That turned out to be the case but the study went further. After six weeks the mice received opioid-blockers that caused them to experience withdrawal symptoms such as shaking and tremors.The mice even avoided the spot where the drug had been administered, an additional possible indication of addiction-related behavior.
"It's surprising that we're genetically programmed to become addicted to something as dangerous as UV radiation, which is probably the most common carcinogen in the world," Fisher said. "We suspect that the explanation involves UV's contribution to vitamin D synthesis in the skin. However, in the current time, there are much safer and more reliable sources of vitamin D that do not come with carcinogenic risk, so there is real health value in avoiding sunlight as a source of vitamin D."
He added that "This information might serve as a valuable means of educating people to curb excessive sun exposure in order to limit skin cancer risk as well as accelerated skin aging that occurs with repeated sun exposure."
"Our findings suggest that the decision to protect our skin or the skin of our children may require more of a conscious effort rather than a passive preference."
