For many pet owners, seeing their dogs chase incessantly after their own tails and hunt shadows may seem adorable. But researchers in Canada, Finland, and France think that the causes of such behavior may be more sinister. They say that these behaviors may be symptoms of the canine equivalent of obsessive compulsive disorder.

Published in PLoS One, the study involved detailed questionnaires filled out by 368 dog owners in Finland. Of the entire group, 150 of the dogs were deemed not to have compulsions, and were used as controls. Researchers also took blood samples of 181 of the dogs profiled in the questionnaires. All of the dogs belonged to one of four breeds: standard and miniature Bull terriers, Staffordshire bull terriers, and German shepherds.

The researchers said that many of the characteristics of canine compulsive disorder are similar to that of humans. Many of the dogs began to show symptoms before they reached sexual maturity. Some of the dogs only had one or two episodes during their entire lives, while others engaged in these behaviors for hours each day. Pups that came from the same litter also had similar behaviors, indicating a genetic component to the disorder. Some breeds had more cases of the disorder than others, and most dogs, if they had canine compulsive disorder, had a milder form.

The researchers also wrote in their study that dogs who received nutritional supplements expressed fewer bouts of tail chasing than other dogs. Neutered female dogs often chased their tails less often, prompting researchers to believe that there may be an ovarian hormone component as well.

But the conclusion made by the study authors is not universally agreed upon. Perminder Schadev, the director of the Neuropsychiatric Institute of the Prince of Wales Hospital in Australia, said to Scientific American that humans, unlike animals, often recognize these behaviors and attempt to modify or control them. Schadev theorized that these behaviors were probably more linked to the repetitive behaviors that characterize another disorder: autism spectrum disorder.