Cat people have always said it: my cat knows when I'm sad. Now a small study from Japan suggests there might be something to it, and it's written in their hormones.
Researchers from Kyoto University and Azabu University followed 19 owners and their 29 cats for a month. They tested urine samples from both, looking at oxytocin, the “cuddle” hormone tied to bonding, and cortisol, a stress hormone. Owners filled in mood questionnaires, and the cats wore little Bluetooth tags that measured how close they stayed to their human's phone. Yes, the cats were wearing trackers. No, nobody told them.
What they found
Owners with more oxytocin tended to live with cats with more oxytocin too. And cats with higher oxytocin lived with owners who reported less anger, anxiety and gloom. Stressed owners, with higher cortisol, tended to have cats with lower oxytocin.
Here's the sweet part: owners felt better not because they'd had their cat for years, but because the cat stayed physically close day to day. The more time the cat spent near them, the more “vigor” owners reported.

Different from dogs
In dogs, owner and pet stress levels are known to move together. In cats, the cortisol link was weak. The researchers wonder if that's because cats and dogs became our pets in very different ways.
Before you tell your friends
This was a small study, and it shows a link, not cause and effect. The authors themselves call it “preliminary evidence”. Lead author Saho Takagi says the feeling owners describe “may be partly reflected in the hormonal connection between cats and their owners.”
So tonight, let the cat sit on your lap. Not for science. For both of you.