Not all dogs cope well when their owners leave them at home. Some get so anxious they end up barking all day long, while others destroy the house and precious objects in their cooped-up state. Still, pinning it down to 'separation anxiety' isn't particularly helpful for pet owners.

Instead, new research suggests this is just a symptom of other underlying frustrations, like wanting to get away from something in the house, wanting to get to something outside, reacting to external noises or events, or even boredom.

"Thus," the study authors write, "there is a danger that a syndrome such as 'separation anxiety' is seen as a diagnosis, when the relative significance of emotions such as fear, frustration and the panic associated with loss of an attachment figure may be fundamentally important to understand for effective treatment."

Separation-related problems are quite common in dogs - somewhere between a quarter to half the general population show these signs.

Such cases are relatively easy to identify - it's hard to miss a number two on your carpet when you come home, after all - but what's less obvious is how we should define separation anxiety, separation-related disorders, and separation-related problems.

This inconsistent terminology along with the fact there is no clear diagnostic test means that studying this issue is incredibly difficult, and the results so far have been confusing, inconsistent, and even contradictory.

The authors point out, for instance, that while some studies indicate neutering as a culprit for these problems, other studies suggest intact dogs are at a higher risk of separation anxiety. The findings of the new research, however, suggest all of these fixes are simply bandaids for a syndrome that is "ambiguously and vaguely defined due to a lack of good empirical data".

In an online questionnaire, the researchers gathered information on more than 2,700 dogs, including over 100 breeds in total.

The large-scale survey included questions that were supposed to illuminate 55 cardinal indications of separation issues, including "exit frustration", "social panic", "elimination", "redirected frustration", "immediate frustration", and "noise sensitivity."

Grouping these dogs into robust hierarchical clusters based on their behaviour, the authors identified four main forms of the condition, each with distinct psychological causes that can be tested and inferred.

Cluster A is the smallest group, and it's characterised by signs of exit frustration, social panic and redirected frustration.

"We propose that the most parsimonious explanation for this profile is that these dogs find being separated aversive (social panic signs) and try to go after the owner (exit frustration), but, because they are unable to do so due to barriers within the home, they struggle to find an alternative way of coping (redirected frustration)," the authors explain.

Cluster B, on the other hand, is characterised by redirected frustration, social panic, and, very rarely, frustration towards the owner, probably because these dogs are highly aroused, want to get at external stimuli and struggle to find an alternative way to cope.

Cluster C is the largest group identified, including over a third of the dogs surveyed, and it's characterised by barking and social panic. Unlike Cluster B, these dogs are aroused by external stimuli, but instead of wanting to get at it, they are more generally anxious and avoidant.

Cluster D is the last group, and, as a result, it's a sort of catch-all basket for those dogs who don't really fit into any of the other clusters. Until we know more about it, the authors suggest we think of it as the "boredom" group. Because yes, even dogs can get bored.

"Labelling the problem of the dog who is being destructive, urinating or defecating indoors or vocalising when left alone as separation anxiety is not very helpful," says veterinarian Daniel Mills from the University of Lincoln.

"It is the start of the diagnostic process, not the end. Our new research suggests that frustration in its various forms is very much at the heart of the problem and we need to understand this variety if we hope to offer better treatments for dogs."

While the study didn't look at the effectiveness of any specific solution, the authors hope this could be a new way to implement more precise and less demanding treatment programs. 

For instance, Mills explains, right now we tend to think of separation anxiety as a single condition - "my dog has got separation anxiety" - and so the focus is on making that dog more independent through treatment. Unfortunately, in many cases that approach completely overlooks the actual issue.

"This new work indicates that having separation anxiety is more like saying 'my dog's got an upset tummy', which could have many causes and take many forms, and so both assessment and treatment need to be much more focussed," says Mills.

"If your dog makes themselves ill by chewing something it shouldn't, you would need to treat it very differently to if it has picked up an infection."

We need to treat separation anxiety in a similar way, he argues, so that pet owners can calmly close the door behind them and not have to worry about what's happening on the other side.

The study was published in Frontiers in Veterinary Science.