It's well-known that music can relieve stress in humans. Studies show it reduces levels of the stress hormone cortisol, and it also boosts the immune system and can be used to treat pain.

Now there's evidence that music can also be beneficial for cats undergoing surgery.

Dr. Miguel Carreira got the idea for the study, which was recently published in the Journal of Feline Medicine and Surgery, after observing cats in his veterinary clinic, where music is always played.

"Different music genres affect individuals in different ways," he said in a news release. "During consultations I have noticed, for example, that most cats like classical music, particularly George Handel compositions, and become more calm, confident and tolerant throughout the clinical evaluation."

To test his theory, Carreira recorded 12 female cats' respiratory rates and pupil diameters at various points during a spaying procedure to gauge the cats' depths of anesthesia.

The felines were fitted with headphones during the surgery and were exposed to two minutes of silence as a control, which was followed randomly by two minutes each of Barber's "Adagio for Strings," Natalie Imbruglia's "Torn" and AC/DC's "Thunderstruck."

The cats were the most relaxed while listening to the classical music and AC/DC's rock song created the most stress, Carreira found. Imbruglia's pop song produced "intermediate values," according to the paper.

Given the findings, Carreira concluded that playing classical music during cats' surgical procedures could be beneficial for the animals.

"Use of certain music genres in the surgical theatre may contribute to a decrease in the anesthetic dose required, reducing undesirable side effects of anesthetic agents and thus promoting patient safety," he writes.

He and his colleagues plan to continue their research by studying the influence of music on other physiological parameters, including cortisol, on both cats and dogs.

Carreira isn't the first to study the effects of music on cats. Recently, psychologists at the University of Wisconsin-Madison teamed up with musicians at the University of Maryland to create music for domestic cats.

By studying felines' natural vocalizations and matching the sounds to music, they created the first species-specific songs. The music is written in three different styles — kitty ditties, cat ballads and feline airs — and is designed to evoke a particular mood in feline listeners while being pleasant to human ears.

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