While Northern Ireland has been basking in glorious sunshine this week, scientists have been explaining how the rays of the sun can have a “heroin” effect on the body.
According to new research findings published by Harvard Medical School in the US, ultraviolet (UV) rays from the sun act like an addictive drug – stimulating the production of “feel good” endorphins that act on the same biological pathways as opioid narcotics.
The study suggests that the desire to bake for hours on a beach involves more than topping up a tan.
It may appease our craving for a sunshine “fix”, in much the same way as an addict satisfies a yearning for heroin or morphine.
Lead scientist Dr David Fisher said: “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 ageing 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.”
Experts had known that sun-seeking behaviour can fit the clinical criteria for a substance-related disorder. But what underlay this apparent “addiction” had been unknown until now.
Dr Fisher and his team investigated links between UV exposure and the opioid receptor pathway in “naked” laboratory mice.
After a week in the artificial sunshine, endorphin levels in the blood of shaved animals increased.
At the end of six weeks, the mice were given an opioid-blocking drug. Abruptly denied the drug-like effects of UV, they suffered an array of withdrawal symptoms including shaking, tremors.
“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,” said Dr Fisher, whose findings appear in the journal Cell.
British experts urged caution when extrapolating the results of the research to humans.
Dr Clare Stanford, reader in experimental psychopharmacology at University College London, said: “This study does not provide the sort of evidence needed to show addiction to UV light in mice and it is even less certain that the work predicts addiction in humans.”
Dr Richard Weller of the University of Edinburgh, said: “Mice are nocturnal animals, covered in fur, which avoid the light, so one must be cautious about extrapolating from these experiments to man.
“Nonetheless, the authors discuss some literature suggesting that a similar pathway might also be present in man.”