Sun risk increased by addictive link
New research suggests the sun may be physically addictive.
A study from the United States has shed light on the idea that some UV skin cancer risk could be self-imposed.
Researchers say recent experiments on mice showed they can become addicted to ultra-violet (UV) light.
The study at the Massachusetts General Hospital also showed the animals displayed physical signs of withdrawal when they were denied access to UV.
Some authorities say it may prompt a re-think the sun smart message is delivered in Australia, which maintains the world’s highest rates of skin cancer.
A new paper on the findings has been published in the journal Cell, and Massachusetts General Hospital researcher Dr David Fisher says it shows the sun can be a drug.
“We were able to identify behavioural consequences that looked very much like addiction that were behavioural changes that indicated an endogenous opiate signalling going on,” Dr Fisher told the ABC.
“The mice would become gradually numb to sensory input, just like morphine would have done. Maybe not quite as potently as morphine, but a very similar opiate-like effect.
“We could see that there was a dependency to UV radiation in which abrupt blockage of the opiate pathway using a drug, using the same drug you would give a heroin overdose patient in the emergency room, such an opiate blocking drug in a mouse that has been receiving daily UV radiation actually produced withdrawal symptoms - shaking and chattering and jumping,” he said.
“[These were] types of symptoms that you would similarly see if the mouse had been addicted to an opiate drug like morphine.”
But the researchers say it may not be a bad thing, and our chemical love of sunshine may have been an evolutionary advantage.
Dr Fisher gave some possibilities for its evolutionary basis.
“The likeliest explanation we believe has to do with vitamin D synthesis in the skin,” he said.
“As you know, when UV shines on our skin it participates as chemical synthesis of vitamin D... probably 100,000 years ago, this was an absolutely vital step in producing vitamin D.
“There were not very many dietary sources, only in a few unusual circumstances, and therefore if you happened at the time to live in a location where UV radiation is limited, such as a high latitude geographic place like, let's say northern Europe, then your ability to obtain sufficient vitamin D to live through childhood was probably highly dependent on the ability of UV to a) be delivered to your skin, b) and actually be absorbed into your skin.”
“And this is thought by many people to be the source, the evolutionary source, of light skin, individuals with light skin who don't tan very easily.
“That's one example we can think of where this, you know, the most ubiquitous, the most common carcinogen in the entire world here, apparently, is something that we are inclined to see. It's an amazing evolutionary paradox.”
A spokesperson from Australia's Cancer Council said the study was further evidence that banning the commercial use of tanning beds is a good move for public health.
All state and territory governments have agreed to ban artificial tanning sun beds, and are in various stages of introducing new laws.