It is already known that stress can increase the risk of physical and mental health problems including high blood pressure, heart conditions and depression. New research has now shown that stress may also be behind problems in getting pregnant.
The study was led by Dr. Courtney Denning-Johnson Lynch, Director of Reproductive Epidemiology at Ohio State University. It builds on the team's earlier work that found a link between high levels of stress and reduced likelihood of pregnancy by finding that it is also tied to increased risk of infertility.
For the new findings, the team examined data on 501 couples trying to conceive who were enrolled in the Longitudinal Investigation of Fertility and the Environment (LIFE) Study between 2005 and 2009 at two research centres in the USA. The couples were followed for up to 12 months as they tried to conceive.
As part of the data collection, the female participants, aged between 18 and 40, and free from fertility problems, gave saliva samples the morning after they were enrolled and also the morning after their first period after enrolment. From these samples, the researchers could measure levels of cortisol and alpha-amylase, known biomarkers of stress.
Over the 12 months of the study period, of the 401 women who completed it, 347 (87%) became pregnant and 54 (13%) did not.
When the data was analysed, the researchers found the women with the highest levels of alpha-amylase had a 29% lower chance of becoming pregnant each month, compared with women with the lowest levels.
Also, the women with the highest indicated stress levels were more than twice as likely to meet the clinical definition of infertility, which is not conceiving despite 12 months of regular, unprotected intercourse.
These links remained despite adjusting for possible factors like age, race, income and use of alcohol, caffeine and tobacco while trying to conceive.
Dr. Lynch comments that this is the second time that high levels of the stress biomarker alpha-amylase are associated with women who are less likely to become pregnant, compared with women with low levels, and adds:
"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."
She says she hopes the findings will persuade women finding it difficult to conceive to look for ways to reduce their stress with methods such as meditation, yoga and mindfulness stress reduction. However,she also points out that stress is only one of several potential reasons why a woman may not conceive.
The findings of the study were reported in the journal Human Reproduction.