Dr. Markus Rantala, Ph.D., a professor at the University of Turku in Finland, set out to find whether attractiveness and immunology were linked in women. And, although his findings were a bit disappointing on that subject, he did stumble upon a couple of other gems: women with less stress are more attractive and more fertile.

According to The Daily Mail, the study found that, unlike in men, a strong immune system in women was not associated with being more beautiful, leading researchers to wonder what other biological factors could contribute to perceived attractiveness.

Dr. Rantala and his team found that women who had more cortisol were seen as less attractive and those with less cortisol were seen as more attractive. The study also found that facial attractiveness signals reproductive potential since cortisol can also adversely affect fertility. Therefore, less attractive people are less likely to be fertile because less attractive people are likely to have higher levels of cortisol. Get it?

Cortisol, the hormone associated with stress, is secreted by the adrenal glands and is involved in regulation of blood pressure, immune function, and inflammatory response, among other things. It is commonly referred to as "the stress hormone" because it is secreted at higher levels during stressful situations.

Small, occasional bursts of cortisol are healthy and to be expected. However, when one has higher and more frequent levels of cortisol, it can cause some serious health issues. These include but are not limited to blood sugar imbalances, high blood pressure, and suppressed thyroid function.

The researchers asked 52 Latvian women to take pictures of themselves during fertile times in their menstrual cycles. Then, 18 men rated the photos of the women on a scale from 0 to 11. The results revealed that women with the lowest levels of cortisol consistently ranked as more attractive.

"This would be consistent with many studies in humans that have found that stress has strong negative effect on health, including immune function, heart disease and susceptibility to cancer," said Rantala. "An alternative explanation is that facial attractiveness signals reproductive potential, which is mediated partly by stress hormones."

So maybe people are right. Beauty is more than skin deep. Biology and health may be more closely connected to human perception of beauty than we ever thought.