Sun lovers beware! Chronic exposure to ultraviolet (UV) radiation can release feel-good hormones called endorphins that may lead to physical dependence, tolerance and addiction-like behaviour.
The findings explain why people have an instinctive desire to be in the sun, despite its known health risks.
"Curb excessive sun exposure in order to limit skin cancer risk as well as accelerated skin aging that occurs with repeated sun exposure," said senior author David Fisher of Massachusetts General Hospital and Harvard Medical School, US.
According to a study, UV exposure stimulates the production of endorphins, which relieve pain by activating opioid receptors through the same pathway activated by prescription painkillers, morphine and heroin.
Fisher and his team examined whether this pathway could underlie UV addiction.
They exposed shaved mice to UV light for six weeks and found that endorphin levels in the bloodstream increased within a week.
After six-week period, treatment with an opioid-blocking drug caused withdrawal symptoms, including shaking, tremors and teeth chattering in mice that had been exposed to UV light.
Researchers 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," Fisher advised.
