Sitting in the sun is linked to days when people lived in caves, scientists believe

August 7, 2017 by Rich Schneider, Indiana University
Sunbathers on a beach. Credit: Indiana University

Summer is in full stride, with people heading to beaches to soak up the sun. But there's more to that behavior than trying to get a good tan, says an epidemiology expert at Indiana University-Purdue University Indianapolis.

The scientific community theorizes that sitting in the sun is an addictive, pleasure-producing behavior driven by a biological mechanism that developed when people lived in caves, according to Jiali Han, the Rachel Cecile Efroymson Professor in Cancer Research at the Indiana University Melvin and Bren Simon Cancer Center and professor and chair of the Department of Epidemiology at the Richard M. Fairbanks School of Public Health.

According to Han, the theory is that people turned to caves thousands of years ago for safety and warmth. But staying in those caves reduced their exposure to sunlight, which produces the Vitamin D needed for bone and reproductive health.

"So we think that this sun-seeking behavior was an evolutionary development," Han said.

The sun-seeking phenomenon comes from a that is triggered when people are exposed to sun or ultraviolet light, Han said. The top layer of the produces beta-endorphin, a hormone, which is then released into the bloodstream. When beta-endorphin reaches the brain, it makes people feel happy, acting on the same biological pathway as other addictive substances like tobacco and alcohol.

"People feel happy in the sun," Han said. "We go out into the sun, feel happy and want to stay in the sun longer.

"In other words, exposure to sun or UV light induces an opioid response that is associated with tanning addiction," Han said.

Han's research group is investigating the molecular pathways and relevant genes for this behavior.

The urge to be in the sun for hours on a beach occurs even among people whose skin burns, rather than tans, according to Han. "They get a burn, but they still want to do it because they feel addicted to it."

When summer ends, that craving for sunshine continues for many people, who then turn to indoor tanning beds, according to Han.

In a paper published in the Journal of Dermatological Science, Han reported that white female college students in Indiana who tan indoors know they are placing themselves at risk of and premature skin aging, but most continue to tan indoors anyway.

Among the study's findings:

  • 99.4 percent agreed that tanning can cause skin problems such as premature aging and skin cancer.
  • 83.6 percent of survey respondents between the ages of 18 and 30 at Indiana University's campuses in Bloomington and Indianapolis agreed that a tan makes them feel more attractive.
  • 83 percent agreed that compared to how they feel before tanning, they feel more relaxed and pleasant during tanning.

Fulfilling a sunshine fix carries a significant danger. "Exposure to the sun is a known causal factor for skin cancer," Han said.

According to Han, one out of five Americans will get skin cancer in their lifetime, even though skin is preventable.

"You should try to avoid exposure to the sun," Han said, offering these tips: "Wear a hat, long sleeves and pants, and frequently apply sunscreen—the higher the SPF, the better."

Explore further: Study shows risk of skin cancer doesn't deter most college students who tan indoors

Related Stories

Study shows risk of skin cancer doesn't deter most college students who tan indoors

January 10, 2017
White female college students in Indiana who tan indoors know they are placing themselves at risk of skin cancer and premature skin aging, but most continue to tan indoors anyway, according to a study conducted by researchers ...

There's no such thing as a safe, healthy tan

June 8, 2017
Dear Mayo Clinic: My daughter wanted to go to a tanning bed before prom, but, instead, she opted for a spray tan. But a lot of her friends are going to a tanning bed and think it's relatively safe. Is there such a thing as ...

Tanning's allure tied to other addictions

March 31, 2017
(HealthDay)—People who seem to have a deep tan year-round—whether from the sun or indoor tanning—may be "addicted" to tanning. And new research suggests there's also a link between such tanning and other addictions.

Should there be age restrictions on tanning beds?

December 29, 2015
Earlier this month, the Food and Drug Administration proposed steps to prevent the use of indoor tanning beds. They want to restrict usage to people 18 years of age and older, and they want tanning bed manufacturers and facilities ...

Images of health risks make indoor tanning messages more effective

April 24, 2017
Although the health risks associated with indoor tanning are clear, tanning bed use among college-aged women is still popular. A new study by UNC Lineberger Comprehensive Cancer Center researchers suggests that adding images ...

Many still tanning, despite dangers, survey finds

May 28, 2012
(HealthDay) -- Despite public education efforts, many young adults still don't understand the dangers of sun exposure and tanning, a new U.S. survey finds.

Recommended for you

Sweet, bitter, fat: New study reveals impact of genetics on how kids snack

February 22, 2018
Whether your child asks for crackers, cookies or veggies to snack on could be linked to genetics, according to new findings from the Guelph Family Health Study at the University of Guelph.

The good and bad health news about your exercise posts on social media

February 22, 2018
We all have that Facebook friend—or 10—who regularly posts photos of his or her fitness pursuits: on the elliptical at the gym, hiking through the wilderness, crossing a 10K finish line.

Smartphones are bad for some teens, not all

February 21, 2018
Is the next generation better or worse off because of smartphones? The answer is complex and research shows it largely depends on their lives offline.

Tackling health problems in the young is crucial for their children's future

February 21, 2018
A child's growth and development is affected by the health and lifestyles of their parents before pregnancy - even going back to adolescence - according to a new study by researchers at the Murdoch Children's Research Institute, ...

Lead and other toxic metals found in e-cigarette 'vapors': study

February 21, 2018
Significant amounts of toxic metals, including lead, leak from some e-cigarette heating coils and are present in the aerosols inhaled by users, according to a study from scientists at Johns Hopkins Bloomberg School of Public ...

Why teens need up to 10 hours' sleep

February 21, 2018
Technology, other distractions and staying up late make is difficult, but researchers say teenagers need to make time for 8-10 hours of sleep a night to optimise their performance and maintain good health and wellbeing.

2 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

RobertKarlStonjek
not rated yet Aug 07, 2017
Humans never lived in caves. They may have sheltered in caves and occasionally stayed in the entrance of a cave but generally humans were nomadic...obviously they couldn't take their cave with them...
tj10
not rated yet Aug 28, 2017
"So we think that this sun-seeking behavior was an evolutionary development."

This article is SO BAD - I can't believe it cleared peer review!

Utter silliness & hubris! As if these cave dwelling people didn't realize the sun was good for them and never spent any time outdoors. When they were finally on the brink of extinction, evolution saved them with a mutation that suddenly gave one of them a desire for sunlight! All hail Evolution, our great Creator!

Just because they lived in caves doesn't mean they spent all their time there & never got any sun! Why condescendingly assume these people were stupid & didn't know that sunlight was important? Maybe they were smart & didn't want to get cancer! Many people today often spend all day indoors on hot sunny days on purpose!

Or, maybe evolution is working to save them from skin cancer? Evolution explains both behaviors equally well, so?

Real scientists always tests their hypotheses. We're waitin

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.