A link between stress and infertility has been confirmed by a new study from Ohio State University's Wexner Medical Center.

The research, led by Courtney Denning-Johnson Lynch, director of reproductive epidemiology at the medical center, corroborates and continues the work of an earlier study by scientists in the United Kingdom who found high levels of stress reduced the ability to conceive.

The new findings, which appear online in the journal Human Reproduction, offer greater understanding of how stimuli impact the human reproductive system; they further suggest stress can actually increase the risk of infertility.

The study has been published online in the journal Human Reproduction.

Lynch and her research colleagues discovered women with high levels of alpha-amylase, a biological indicator of stress that's measured in saliva, are 29 percent less likely to get pregnant each month and, compared to women with low levels of the protein enzyme, are more than twice as likely to meet the clinical definition of infertility: not becoming pregnant, despite 12 months of regular, unprotected intercourse.

Researchers recruited 501 American women -- aged 18 to 40 years, who reported being free from known fertility problems and had just started trying to conceive -- and followed them for 12 months or until they became pregnant.

Saliva samples were collected from participants the morning following enrollment as part of the Longitudinal Investigation of Fertility and the Environment Study and again the morning following the first day of their first study-observed menstrual cycle.

Saliva specimens were measured for the presence of salivary alpha-amylase and cortisol, two biomarkers of stress.

The testing revealed "women with high levels of the stress biomarker salivary alpha-amylase have a lower probability of becoming pregnant, compared to women with low levels of this biomarker. For the first time, we've shown that this effect is potentially clinically meaningful, as it's associated with a greater than two-fold increased risk of infertility among these women," said Lynch in a university news release.

The new study, said Lynch, should encourage women who are experiencing difficulty getting pregnant to seek out better ways to handle their stress levels, including the use of known stress-reducing techniques like yoga, meditation and mindfulness, a psychological exercise where a practitioner pays attention to the present on a moment-to-moment basis.