A study published on Thursday found that chronic exposure to
ultraviolet radiation triggers the release of endorphins - the
so-called feel-good hormones - that function through the same
biological pathway as highly addictive opiate drugs such as heroin
The study involved laboratory mice, but the researchers said they
believe the findings are applicable to people because the biological
response of skin to UV radiation in mice is so similar to humans.
Regular UV radiation exposure led to physical dependence and
addictive behavior in the mice, the study found. The animals even
exhibited withdrawal symptoms - shaking, tremors and teeth
chattering - after being treated with a drug that blocked the
endorphin activity, the researchers said.
Writing in the journal Cell, they said the addictive nature of UV
exposure "may contribute to the relentless rise in skin cancer
incidence in humans."
"There is this dangerous addictive pathway operating," said
dermatologist Dr. David Fisher of Massachusetts General Hospital and
Harvard Medical School, who led the study.
Fisher said in theory sun-related skin cancer should be highly
preventable merely by reducing exposure, but the addictive qualities
of UV exposure may help explain the dogged "sun-seeking behavior"
some people display through outdoor and indoor tanning and other
"Behavioral exposure to the sun is being guided by influences that
go past just a desire to have a nice game of Frisbee outside.
There's something else motivating that behavior," Fisher added.
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Exposure to ultraviolet rays through sunlight and indoor tanning
equipment is considered a major risk factor for skin cancer
including melanoma. The American Cancer Society said U.S. melanoma
rates have been rising for at least 30 years, with about 76,000 news
cases and 9,700 deaths forecast for 2014.
Cumulative damage from UV radiation also can cause premature skin
aging in the form of wrinkles, lax skin and brown spots.
Exposure to UV rays stimulates production of endorphins - the same
hormones stimulated by activities like vigorous exercise. They turn
on opiate-related receptors via the same biological pathway
triggered by prescription painkillers and other opiate drugs.
The researchers shaved the backs of the mice and gave them a daily
dose of UV light – enough to induce tanning but not burning - for
six weeks. Bloodstream endorphin levels rose within a week.
John Overstreet, executive director of the Indoor Tanning
Association, said the study "ignores the benefits of exposure to
ultraviolet light, the most obvious of which is the production of
vitamin D through your skin."
"It is also important to note that there is no simple definition of
addiction and the identification of addictions requires a
substantial body of research. It is highly unlikely that a single
study could lead to a sound conclusion on the matter. You can take
anything too far, that does not mean it is an addiction," Overstreet
SOURCE: http://bit.ly/1iLJpal Cell, online June 19, 2014.
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