Short sessions of mindfulness meditation reduce mental stress, say researchers who can now confirm what practitioners have long believed.

Researchers at Carnegie Mellon University found that meditating for 25 minutes for three days can significantly lower stress and boost the ability to endure stress.

"More and more people report using meditation practices for stress reduction, but we know very little about how much you need to do for stress reduction and health benefits," lead author J. David Creswell, associate professor of psychology in the Dietrich College of Humanities and Social Sciences, said in a press release.

The study was conducted on 66 healthy participants aged between 18 and 30. They were told to take part in a three-day experiment where some participants underwent mindfulness meditation training programs for 25 minutes for three consecutive days. Others were told to learn breathing exercises that could help monitor their breath and pay attention to their present moment experiences. The researchers also included a matched control group where participants were told to improve their problem-solving skills through poetry analysis.

Following their programs, participants were given tasks to complete stressful speech and math in front of "stern" researchers who recorded their stress levels by measuring cortisol levels in saliva samples.

The study findings showed that people in the mindfulness meditation group were less stressed when performing speech and math tasks. However, these participants also showed greater cortisol reactivity in saliva samples.

"When you initially learn mindfulness mediation practices, you have to cognitively work at it - especially during a stressful task," said Creswell. "And, these active cognitive efforts may result in the task feeling less stressful, but they may also have physiological costs with higher cortisol production."

The findings were published in the journal Psychoneuroendocrinology.