Dec. 6, 2005 -- Stress plus the sun's damaging rays could raise the odds of skin cancer.
That's what researchers report in the Journal of the National Cancer Institute.
They exposed stressed and nonstressed mice to harmful UVB rays. The stressed mice developed skin cancer more quickly and showed weaker immune systems.
"Our results show that a moderate chronic stressor, one that does not ... change body and organ weights, can substantially increase susceptibility to cancer," write Firdaus Dhabhar, PhD, and colleagues.
Dhabhar works at Ohio State University in the Colleges of Medicine and Public Health, Dentistry, and the Institute of Behavioral Medicine Research.
Stress, Sunlight Common
Stress and sunlight are part of daily life for many people, the researchers write. They add that both can be beneficial in moderation and harmful in excess over the long run.
To study stress, sunlight, and skin cancer, they first exposed hairless female mice to UVB light from sun lamps three times a week for 10 weeks.
Next, they put some of the mice under stress. Those mice were restrained in their cages for six hours daily for three weeks, roughly midway through the experiment. The restrained mice were given adequate ventilation and their bodies were not compressed.
The stress was largely psychological, since mice don't like being confined, the researchers note.
The mice were monitored for about eight months. For comparison, another group of mice wasn't stressed or exposed to UVB light.
Stressed Mice Got Skin Cancer Faster
Repeated exposure to UVB light prompted skin cancer in the mice, as expected.
The genes that produce those protective chemicals were also suppressed in the stressed animals, according to the study.
The researchers write that stress may have hampered the mice's immune systems, increasing vulnerability to cancer-causing UVB exposure. They call for more studies to check their results.
Stress Not Solely to Blame
Stress wasn't tested by itself, so it's not single-handedly being blamed for skin cancer. The mice were all exposed to light that's known to cause skin cancer.
However, the chronic stress was only given for a relatively brief time (21 days). The increased odds of skin cancer in the stressed mice emerged several months later.
They say the findings are the first of their kind and could be important for other conditions affected by chronic stress.