College is stressful. Students have classes, exams and so many other pressures common in modern life and now researchers have found that petting dogs and cats can improve students' mood with stress-relieving physiological benefits, a study shows.

According to the study published in the journal AERA Open, many universities have instituted "Pet Your Stress Away" programmes, where students can come in and interact with cats and dogs.

"Just 10 minutes can have a significant impact," students in our study that interacted with cats and dogs had a significant reduction in cortisol, a major stress hormone," said Patricia Pendry, Associate Professor at Washington State University.

The study involved 249 college students randomly divided into four groups. The first group received hands-on interaction in small groups with cats and dogs for 10 minutes. They could pet, play with and generally hang out with the animals as they wanted.

To compare effects of different exposures to animals, the second group observed other people petting animals while they waited in line for their turn. The third group watched a slideshow of the same animals available during the intervention, while the fourth group was "waitlisted".

According to the researchers, those students waited for their turn quietly for 10 minutes without their phones, reading materials or other stimuli, but were told they would experience animal interaction soon.

For the findings, several salivary cortisol samples were collected from each participant, starting in the morning when they woke up.

Once all the data was crunched from the various samples, the students who interacted directly with the pets showed significantly less cortisol in their saliva after the interaction.

These results were found even while considering that some students may have had very high or low levels to begin with.

"What we wanted to learn was whether this exposure would help students reduce their stress in a less subjective way. And it did, which is exciting because the reduction of stress hormones may, over time, have significant benefits for physical and mental health," Pendry said.