Even treats aren’t as much fun for traumatized pups.

A heartbreaking new study finds that screaming at dogs scares them for the long term — and patience is a far superior method for training them, Science Alert reports.

Researchers, led by biologist Ana Catarina Vieira de Castro of the Universidade do Porto in Portugal, recruited 42 dogs from schools that used reward-based training, and 50 dogs from aversion training schools.

During the study period, pups taught with yelling and leash-jerking were found to be more stressed, with higher levels of cortisol found in their saliva.

“Our results show that companion dogs trained using aversive-based methods experienced poorer welfare as compared to companion dogs trained using reward-based methods, at both the short- and the long-term level,” the researchers write in the paper published by biology news service bioRxiv.

“Specifically, dogs attending schools using aversive-based methods displayed more stress-related behaviors and body postures during training, higher elevations in cortisol levels after training, and were more ‘pessimistic’ in a cognitive bias task,” researchers found.

Pups that experienced calm, gentle teachers, however, performed better at tasks that researchers assigned to them, such as locating a bowl with sausage in it — in a roomful of empty but sausage-smeared bowls.

More harshly trained canines were slower to locate the treat bowl, which authors interpreted as showing that their experiences had made them more depressed, less hopeful hounds.

The biologists also analyzed dogs during training to look for “stress behaviors” such as lip-licking, paw-raising, yawning and yelping.

“Critically, our study points to the fact that the welfare of companion dogs trained with aversive-based methods appears to be at risk,” the researchers conclude.