Trainspotting's heroin addicts would have suffered worse cravings due to the lack of sunshine in Scotland, researchers say.
Danny Boyle's acclaimed 1996 film saw Ewan McGregor's character Mark Renton's family make him go cold turkey.
But a study found a tanning salon or sunny getaway would have been better for the 26-year-old's battle with the highly-addictive Class A drug.
Massachusetts General Hospital researchers found a lack of Vitamin D "strongly exaggerates" the cravings for and effects of opiods.
They suggested the link between opioids and sun-lovers could go back to the cavemen who first inhabited northern areas like Scotland evolving to enjoy soaking up rays.
Experts have suggested people develop urges to sunbathe and visit tanning salons that mirror the behaviors of opioid addicts.
Dr David Fisher and his team – who are behind the study – were stunned when they first found exposure to UV rays caused the skin to produce the 'feel good' hormone endorphin.
It's chemically related to morphine, heroin and other opioids – and the researchers found they all act on the same receptors in the brain in 2007.
Dr Fisher's team has now shown that UV exposure raises endorphin levels in mice which then act like they were addicted to opioids.
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He and his colleagues now think that sun addiction might be a real thing after all as people can end up craving the endorphin rush from soaking in UK-B rays.
But as humans and mice can't have evolved to seek out these rays as they cause skin cancer, wrinkles and other skin conditions, the academic asked: "Why would we evolve to be behaviorally drawn towards the most common carcinogen that exists?"
He believes that the only explanation for why humans and other animals seek out the sun is that exposure to UV radiation is necessary for production of vitamin D, which our bodies can't formulate on their own.
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Vitamin D promotes uptake of calcium, which is essential for building bone.
The first people to inhabit Scotland and other northern areas of the world may have evolved a need to step out of their caves to absorb the sun for the Vitamin D, Dr Fisher reckons.
A lack of the vitamin could be fatal to small children and weakened bones which would shatter when people ran from predators.
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The study lead author Dr Lajos Kemény said: "Our goal in this study was to understand the relationship between vitamin D signaling in the body and UV-seeking and opioid-seeking behaviour.
"We found that modulating vitamin D levels changes multiple addictive behaviors to both UV and opioids."
The study also found that morphine worked more effectively as a pain reliever in mice with vitamin D deficiency leaving them more likely to become addicted.
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Previous analysis of health records found patients with modestly low vitamin D levels were 50 percent more likely than others with normal levels to use opioids.
Those with severe vitamin D deficiency were 90 percent more likely.
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