Prevalence, comorbidity, and breed differences in canine anxiety in 13,700 Finnish pet dogs

We have here developed a comprehensive behavioural survey and applied a citizen science approach to collect a large canine behavioural dataset of over 260 breeds of dogs. Our data replicates results from some earlier studies and the study also shows a number of novel insights, including prevalences, comorbidities and breed differences of traits not described before. These results improve the overall understanding of problematic behaviour.

Based on the results here and in previous studies, noise sensitivity stands out as the most common canine anxiety with a prevalence of 32% in this study. Earlier, the prevalence has varied between 20% and 50%9,12,14,15,16,17,18. Based on our study and previous studies14,17,18, the most common noise sensitivity is the fear of fireworks. Fear was the second most common canine anxiety, with a prevalence of 29%. Specifically, 17% of dogs showed fear of other dogs, 15% fear of strangers and 11% fear of novel situations. Prevalence of total fearfulness12,16 and prevalence of fear subtraits9,15,16,35 were quite similar in previous studies as well. Fear of surfaces and heights appears to be highly prevalent in our study population, as 23.5% of dog owners reported that their dogs were highly fearful of different surfaces and heights.

Based on our results, every fifth dog displays high levels of inattention and 15% high levels of hyperactivity/impulsivity. Excessive activity has been reported in 12% to 34% of dogs9,12. Compulsive behaviour patterns were observed in 16% of the dogs, agreeing with a previous study9. Based on our results and previous studies9,28, self-mutilation is the most common compulsive behaviour. Self-mutilation may be a compulsion, but it may also be caused by allergies, ectoparasites or other skin problems, possibly explaining the high prevalence of the subtrait.

The prevalence of aggression was 14%, with both aggression toward human family members and toward strangers occurring in 6% of dogs. In our previous study, 16% of dogs had at least once displayed aggressive behaviours toward family members and 45% toward strangers16. In previous studies, the prevalence of aggression and its subtraits has varied between 2% and 30%9,12,15. Studies focusing on referrals to veterinary/behaviour clinics often report aggression as the most common behaviour problem10,11,13, possibly because owners find aggressiveness more problematic than, for example, fear of fireworks. Separation related behaviours were only displayed by 6% of the dogs. Previously, the prevalence of separation anxiety has been 2–3 times higher than in this present study9,15,16,19, possibly because we only included dogs with high frequencies of separation related behaviour. Taken together, our results are surprisingly similar compared to previous studies, even though the populations studied and the criteria for anxiety-related traits differ in every study.

Male and female dogs displayed differences in the prevalence of behaviour problems. Male dogs had a higher prevalence of aggressiveness, separation related behaviour, inattention and hyperactivity/impulsivity. In contrast, female dogs had a higher prevalence of fearfulness. Noise sensitivity, fear of surfaces and compulsive behaviour occurred independent of sex. Previous studies have shown similar sex differences in aggression9,13,36,37,38, fearfulness13,32,39,40,41, separation related behaviour36 and compulsion33. Reported sex differences in noise sensitivity are less clear (more common in females17,32, more common in males14, no difference between sexes18).

We detected differences between age groups in the prevalence of most behaviour problems. Younger dogs had a higher prevalence of destroy/urinate when alone, inattention, hyperactivity/impulsivity, tail chasing and self-biting. Older dogs had a higher prevalence of aggression, noise sensitivity and fear of surfaces. Fearfulness was most common in dogs aged 4–8 years. Furthermore, vocalize/salivate/pant when alone and other compulsive behaviours (beside the aforementioned tail chasing and self-biting) occurred independent of age. Previous studies are in agreement at least in noise sensitivity14,17,18,32, inattention42,43, hyperactivity/impulsivity12,42,43,44 and aggression12,37. Tail chasing, destroying and urinating indoors are typical behaviours for puppies, and this likely explains the age differences in these subtraits.

We observed large behavioural differences between breeds. Noise sensitivity was the most common in Lagotto Romagnolo, Wheaten Terrier and mixed breed dogs. Previous studies have also ranked these breeds high in noise sensitivity14,16,17,18. Among some other breeds, Miniature Schnauzers and Staffordshire Bull Terriers were, in contrast, noise sensitive less often, as also observed in previous studies10,17. Fear was most common in Spanish Water Dogs, Shetland Sheepdogs and mixed breeds. In contrast, Labrador Retrievers were seldomly fearful. These results are in agreement with previous studies, ranking mixed breed dogs high in fearfulness9,13,35,40 and Labrador Retrievers and Staffordshire Bull Terriers low in fearfulness35,41,45,46. Fear of surfaces and heights was the most often observed in Rough Collie and mixed breed dogs.

Inattention was most often reported in mixed breed dogs, Finnish Lapponian Dogs and Lapponian Herders, and rarely reported in Spanish Water Dogs and Border Collies. Although Finnish Lapponian Dogs and Lapponian Herders have not been studied before, our results agree with previous results43. As the dog breeds showing high prevalence of inattention are breeds that are often regarded as “hard to train”, owners may rate dogs not easily motivated by food or petting as inattentive. Hyperactivity and impulsivity were the most common in mixed breed dogs, German Shepherds, Spanish Water Dogs and Staffordshire Bull Terriers, and the least common in Rough Collies and Miniature Schnauzers. Similar breed differences were observed in a previous study44. Furthermore, herding dogs (including, for example, Border Collie and German Shepherd) and terriers (including, for example, Staffordshire Bull Terriers) have ranked high in extraversion and, in contrast, toy dogs low in extraversion47. In our study, Labrador Retrievers and Rough Collies had a low prevalence of hyperactivity/impulsivity, but otherwise our results match previous studies. However, it seems that classification into traditional and genetic breed groups poorly reflect behavioural differences48, possibly explaining the differences in these results. Compulsive behaviour was most often reported by owners of German Shepherds, mixed breed dogs and Staffordshire Bull Terriers. However, the breed differences varied highly between different compulsions. For example, Staffordshire Bull Terriers had a high prevalence of tail chasing, with nearly 10% of them chasing their tails. In contrast, light chasing and staring were the most often observed in Border Collies. Interestingly, Border Collies were bred to herd livestock by staring at them intensely, and even though this method of herding can be perfected by training, the behaviour itself seems to be innate49. Pacing and excessive drinking were often performed by mixed breed dogs and German Shepherds. In a previous study, German shepherds had high odds of being presented to a behaviour clinic for obsessive behaviour10.

Mixed breed dogs and Miniature Schnauzers had the highest prevalence of aggression, whereas Labrador Retrievers had the lowest prevalence of aggression. Aggression toward strangers was most prevalent in Miniature Schnauzers, mixed breed dogs, German Shepherd Dogs and Spanish Water Dogs, and least prevalent in Labrador Retrievers. Aggression toward human family members was most common in Miniature Schnauzers and Lagotto Romagnolos. Our results agree with previous studies both in total aggression9,13 and in the subtraits, aggression toward strangers36,37,38,45 and aggression towards family members16,37. Separation related behaviour was most common in mixed breed dogs and Wheaten Terriers. Specifically, mixed breed dogs were likely to destroy, urinate or defecate when left alone, whereas Wheaten Terriers were likely to vocalize, salivate or pant. Based on our results and a previous study36, mixed breed dogs may be more prone to show separation related behaviour. It is possible that the high prevalence of separation distress and other anxieties in the mixed breed dogs is caused by a poor early life environment and adverse experiences in life, as many mixed breed dogs in our data are likely rescues.

Within-trait comorbidity was common in noise sensitivity and fear: 53% of dogs that were fearful of one noise were fearful of several noises, and 38% of fearful dogs were fearful of more than one target. This result was also discovered in our previous study16. Based on previous studies, noise sensitivity is often generalised and displayed toward several different noises9,14,17,18. We discovered that dogs were seldomly aggressive toward both family members and strangers, as reported before in some dog breeds50. In contrast, one previous study did report a significant comorbidity between stranger-directed and owner-directed aggression13. However, it seems that aggression toward strangers and family members are genetically distinct traits51.

We discovered that noise sensitivity and fear were the most common comorbidities, likely due to their high prevalence in our study population. However, when comparing the risk ratios in comorbid traits, the largest risk ratios were seen between separation related behaviour, hyperactivity/impulsivity, inattention and compulsive behaviour, and between fear and aggression. Fearful dogs were 3.2 times more often aggressive than non-fearful dogs, a relationship found in previous studies as well9,13,16,38. This indicates that aggression is commonly motivated by fear. The connection between impulsivity, compulsive behaviour and separation related behaviour is an interesting finding that demands further research. One previous study discovered that excitable dogs had 9.8 times higher odds of separation distress52 and another study discovered a connection between compulsive behaviour and hyperactivity9. Intriguingly, impulsivity and compulsion are related constructs, as both are proposed to be caused by a failure of response control and mediated by basal ganglia53. We observed many trait connections detected in previous studies as well, including comorbidity between fear and noise sensitivity14,16,17, between fear and separation related behaviour16, between separation related behaviour and aggression13,16 and between fear and compulsive behaviour9,33. However, previous studies have detected a comorbidity between separation anxiety and noise sensitivity9,13,15,17,19,20. We indeed discovered that separation related behaviour was 1.4 times more prevalent in noise sensitive dogs. However, the opposite was not true, as dogs showing separation related behaviour were not fearful of noises more often than dogs not showing separation related behaviour. Furthermore, we discovered a positive connection between compulsive behaviour and aggression, contrasting with the results of our previous study33.

This study has limitations. Although the fear section of the questionnaire was validated and the test-retest reliability of the fear and noise sensitivity sections was good54 and that the results we have obtained from the data collected with it32,33,55 replicate many previous results, the psychometric properties of the rest of the questionnaire have not been formally evaluated. Future studies should aim to assess the reliability and validity of these additional components. Secondly, the categorisation into low, moderate, and high categories was mostly based on the frequency of signs and not the severity, except in aggression, separation anxiety, and impulsivity/inattention. Thus, in the high groups, the severity of the symptoms can be variable. Thirdly, our sample is a self-selected convenience sample, and may not be representative of the overall Finnish dog population. Although the most common breeds in our sample are also common in Finland56, the representativeness of our sample is still unknown. We are currently working on a separate study to understand the participant profiles and details of the sample demographics.

Our findings on breed differences indicate that canine anxieties likely have a genetic basis. In previous studies, many behavioural traits have been indeed shown to have small to moderate heritabilities22,26,57 and recently we mapped two loci for generalized fear and noise sensitivity30. Therefore, it could be possible to decrease the prevalence of canine anxieties by selecting non-anxious animals for breeding. Our results also show that these canine anxieties are phenotypically correlated. Some of these traits, like many behaviour traits21,22, may also be genetically correlated, and therefore selection for one trait may influence other traits as well. Interestingly, a genomic region associated with noise sensitivity in German Shepherd Dogs30 contains the oxytocin receptor gene (OXTR). The gene is associated with social behaviour58 (but see a contrasting study with a smaller sample size59) and most likely has been under strong selection during domestication. This could explain the high prevalence of noise sensitivity in many study populations12,14,15,16,17,18 and could also indicate that breeding efforts to reduce the prevalence of noise sensitivity may prove difficult.

Based on our results, canine anxieties and behaviour problems are common across breeds. There are around 77 million dogs in the United States60 and 85 million in Europe61, and therefore these behaviour problems can affect millions of animals. As anxiety can impair welfare1 and problematic behaviour may be an indication of poor welfare62, efforts should be made to decrease the prevalence of these canine anxieties. Breeding policies may help to improve dog welfare, as could changes in the living environment14,19,32,33,37. Our ongoing efforts aim to identify environmental and genetic risk factors behind these canine anxiety-related traits using the large survey data collected here.

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