Sunlight Might be Addictive, Study

A new Harvard study supports the idea that sunlight can be addictive.

Researchers at the Harvard Medical School and investigators at the Massachusetts General Hospital said that their study seconds the theory that sunlight can be addictive. The addiction might explain why people continue to flock beaches during summer to get a tan, despite knowing the risk of elevated risk of skin cancer due UV exposure.

The study was conducted on mice models. Researchers found that chronic exposure to UV light increases circulating level of beta-endorphin in mice. Also, blocking the effect of beta endorphins led to the mice experiencing withdrawal effects.

"Our study identified an organic pathway encoded in skin whereby UV radiation causes the synthesis and release of beta-endorphin and produces opiate-like effects, including addictive behavior," said David E. Fisher, who led the study. "This provides a potential explanation for the 'sun seeking' behavior that may underlie the relentless rise in most forms of skin cancer."

Several studies have shown that frequent tanners show addiction-like behaviors. Studies on mice have implied, but never proved that people can get addicted to UV light.

The present study sought to look at the molecular mechanism behind this addiction in mice models.

According to researchers, exposure to sunlight causes several changes in the body; part of this response is the production of a protein called POMC. This protein is broken down in several fragments, with one kickstarting melanin production, while the other generating beta endorphins. Researchers wanted to know whether these beta endorphins produce opiate-like effects in mice.

Opiates are pain-relieving drugs that work by affecting the central nervous system. Heroin is a commonly abused opiate.

The study found that mice exposed to UV light had reduced sensitivity to pain and high levels of beta endorphins.

Researchers then gave the test mice naloxone, which led to drug-withdrawal like symptoms.

"It is possible that a natural mechanism reinforcing UV-seeking behavior may have developed at certain stages of mammalian evolution through its contribution to the synthesis of vitamin D," said Fisher in a news release. "But such behavioral effects would also carry the carcinogenic risks of UV light that we now recognize. Today's alternative sources of vitamin D, such as inexpensive oral supplements, are both safer and more accurate in maintaining healthy vitamin D levels.

The study was supported by the National Institutes of Health and is published in the journal Cell.