Birth control pills may affect the body’s ability to regulate stress, say researchers

Contraceptive pills may have an impact on the body’s ability to regulate stress, a new study has found.

Researchers from Aarhus University and the United States have studied the stress response of 131 young women by measuring the levels of the stress hormone ACTH in the their blood. Some of the participants were on birth control, while others were not.

The study showed that 15 minutes of social activity after having a blood sample taken lowered stress hormone levels in women who were not on birth control. In contrast, women on birth control did not experience any reduction in their ACTH levels.

To avoid causing any additional stress to the test subjects, a small intravenous catheter was inserted in connection with the first blood sample. The researchers could then draw blood after the social activity without having to prick the women with a needle again.

After having a blood sample taken, they could then participate in one of six different group activities such as playing board games, getting to know each other in a group session, singing songs together or attending a church service.

“Being with other people is one of the most effective ways of reducing stress,” explained Michael Winterdahl, a visiting scholar at the translational neuropsychiatry unit at the department of clinical medicine.

“Our results are important because they indicate that people who use birth control pills do not experience the same reduced stress hormone levels in connection with social activity as people who don’t.”

It has long been established that birth control pills affect the stress response in women. However, looking at the stress hormone ACTH in connection with a social activity is a new approach.

The research differs from previous studies that have primarily focused on the stress hormone cortisol in extreme circumstances.

In this study, scientists measured the stress hormone ACTH, which changes significantly faster than cortisol, making it possible to observe and analyse rapid changes in a person’s stress response.

“By studying ACTH levels, we take another step towards understanding how the brain regulates stress as ACTH acts as a neurotransmitter from the brain to the adrenal cortex, which produces cortisol,” said Winterdahl.

“When we analyse ACTH levels, we can gain insight into the quick-response mechanism that controls the body’s reaction to stress.”

Birth control pills are known for being able to affect the hypothalamic-pituitary-adrenal (HPA) axis. As the name indicates, the stress signal travels from the hypothalamus in the brain through the pituitary gland that releases ACTH to the adrenal glands that release cortisol.

However, researchers still need an explanation to why women on birth control do not experience the same reduction of stress hormone levels in connection with social activities as those who are not on the pill.

Winterdahl said there are several competing hypotheses that try to explain the lower cortisol levels in women on birth control.

“Our research has pushed us closer to an explanation that centres on the brain and the ACTH dynamics. The biochemistry is complex, but we are working based on the assumption that birth control pills can suppress the body’s own production of progesterone.”

The study additionally revealed that the stress response in women who did not take birth control pills depended on where they were at in their menstrual cycle.

The stress-reducing group activities had no effect on the ACTH levels of the women who were in the proliferative phase of their cycle – just after their period has ended and the body begins producing hormones to get ovulation started.

“Progesterone levels are very low during the proliferative phase of a natural cycle. This leads to a minimal conversion of progesterone into the hormone allopregnanolone,” said Winterdahl.

“Since allopregnanolone is important for activating the receptors that regulate the stress response, we don’t see a reduction in ACTH levels in women with a natural cycle who have just had their period.”

He pointed out that women also tend to be more physically active during the proliferative phase which could be seen as an adaption in which the stress response and behaviour change in step with the cycle.

In women on birth control, he said, the stress response is “disconnected”, meaning it can not be adapted to a given situation.

Research still can’t explain exactly how this affects women. Additional studies are needed to clarify the complex mechanisms involved in the correlation between hormone levels and the stress response.

“There are different generations of the pill, each with its own chemical structure due to the hormones used, which means the pills have different side-effect profiles,” Winterdahl concluded.

“It’s therefore crucial that our experiments are reproduced with a larger and more diverse group of test subjects.”