If animals could talk, how would they say they are feeling? While some serene family pets might seem to exist in a perpetual state of bliss, others often appear more conflicted. Sometimes, animals may even appear to display some of the same anxious or compulsive behaviors as humans with clinically, diagnosed mental disorders. But are animals actually experiencing mental illness in the way humans do?
Questions over the extent to which animals can experience mental illness have existed for centuries. Though researchers and everyday dog owners have long speculated about the thoughts that might be taking place behind those sad puppy eyes, modern advances in science and brain scans are providing a clearer picture of just what’s actually going on. Experts now believe most mammals and maybe even some birds can experience anxiety, often in ways surprisingly similar to humans. Those similarities likely only go so far, though.
How animal mental illness compares to the human experience
Veterinarians and animal behavior researchers say animals can experience mental illnesses and psychiatric disorders, but not in exactly the same verifiable ways as humans. Dogs and cats treated for signs of anxiety, for example, may not meet the Diagnostic and Statistical Manual of Mental Disorders (DSM) official definition of “Generalized Anxiety Disorder (GAD)” or chronic anxiety. That definition mentions excessive worrying on more days than not and difficulty controlling worrying. While humans can use language to describe that experience to clinicians, animals can’t communicate like that, at least not yet, anyway. That means we can only really tell if animals experience anxiety or other mental disorders based on our observations of their behavior. Veterinarians can diagnose an animal with anxiety, or obsessive-compulsive disorder when they see potential evidence of it in their actions. They can’t read their minds though, so it’s still uncertain just how many animals might be truly experiencing a mental state one would associate with mental illness.
University of Pennsylvania associate professor and veterinarian Carlo Siracusa emphatically told Popular Science animals “absolutely” can experience mental illnesses. Siracusa regularly works with clients who have dogs and cats that exhibit signs of aggression or destructive behavior which he says is a byproduct of distress or fear. This manifests itself similar to fear-based anxiety seen in humans. In fact, Siracusa says, similar regions that regulate emotions in the human brain are also at work in animals exhibiting signs of anxiety. Though the brains of humans and animals differ in size and complexity, emotional processing in both cases takes place in the amygdala. Like humans, dogs who have been neglected or who have had some other major disruptive change to their environment can show impulsive aggression. Pets, also like humans, can form compulsive behaviors.
But there are still some forms of mental illness that do seem uniquely human. Cases of psychosis like schizophrenia, for example, seem to be tied directly to the complexity of human brains. Though not still completely understood, studies in recent years from researchers at Mount Sinai and elsewhere suggest schizophrenia in particular might be the result of portions of DNA, called “human accelerated regions,” that underwent rapid evolutionary change in humans, but stayed the same in other animals. As far as we can tell, animals other than humans don’t possess the ability to feel “insecure” in social settings or exhibit despair over abstract, existential concepts. This means animals can’t experience specific types of clinical depression possible in humans. Siracusa says this may be because animals lack a very sophisticated prefrontal cortical function necessary for long-term planning. Siracusa said this objective analysis of an animal’s physical brain function was separate from the more philosophical question of whether animals possess so-called self-awareness. That question has been debated for centuries and is difficult to definitely prove.
[Related: A lone dolphin has been yelling into Baltic Sea for years]
Chewing, barking, and shaking: How to spot an anxious animal
Mental illness in animals can present itself in various forms. Unlike humans, who can be diagnosed with Generalised Anxiety Disorder due to a variety of factors, animals are always reacting to their environment in some way. Anxious dogs and cats may pace around a room, tremble, shed fur, or compulsively vomit up meals. Primates in captivity by contrast have been known to throw excrement or engage in sometimes brutal self-mutilation. Siracusa says many of the cases that he sees in the real world involve animals who have manifested their anxieties in a destructive form. In some instances, pets with severe bouts of separation anxiety may get overwhelmed and wage war on the furniture in an apartment. Other severely anxious pets may growl or even attack other unfamiliar people or animals in a fear response. Extreme past traumas can also stick with animals much in the same way they do with humans. As many as 10% of US military dogs who saw active combat in Afghanistan have reportedly received clinical diagnoses of post-traumatic stress disorder.
Often though, Siracusa says animals with mental illness often only get spotted when their behavior is negatively affecting the lives of their owners. In reality, he said, it’s likely there’s a larger cohort of animals suffering from some lower-level anxieties that otherwise go unnoticed. When Siracusa and his colleagues conducted a study looking at how pets respond when they are left alone, he found many spent much of their time parked in front of their dog, nervously awaiting their owner’s return.
“In these cases, they are not destroying [objects], they’re not urinating and defecating,” Siracusa said. “These cases are more likely to be missed because there’s no practical problem.”
When animals go ‘mad’
But mental illness in animals can also present itself in more dramatic ways. Author Laurel Braitman explores many of these cases in her 2014 book, Animal Madness. Braitman, who herself had a dog with a diagnosed case of extreme separation anxiety jump out of a fifth-floor apartment window, provides numerous detailed accounts of animals over the course of the past two centuries acting in compulsive or self-destructing ways one might now associate with mental illnesses. There are numerous instances of anxiety-prone chimps and gorillas repeatedly redigesting their food and eating their own feces. Brian, a young male bonobo located at the Milwaukee Zoo who was isolated from his peers reportedly responded by tearing off his own fingernails and developing a habit of compulsively inserting his hand into his rectum, sometimes enough to draw blood.
Maybe most striking, however, is the case of Tip, an Asian elephant shipped across the Atlantic Ocean to a New York City zoo in the late 1880s. Tip was reportedly abused by his keeper on a regular basis. One day, Tip, who had otherwise seemed docile and calm, lashed out and attempted to stomp his keeper to death. Three years later, Tip attacked again, this time using his tusks to try and gore the same man. Though the keeper narrowly survived both encounters, it sparked a public debate over what to do with the aggressive, so-called “mad” elephant. Newspaper reports at the time cited Tip’s apparent decision to wait three years between attacks as evidence of his supposed vindictiveness and pre-meditated blood lust.
In reality, Tip’s reactionary behavior, like that of other mistreated zoo animals, was likely the cumulative result of being forcibly separated from his groups and enduring an unnatural and likely traumatic sea voyage. The keeper was simply the latest example of a long line of figures Tip may have associated with suffering. Central Park Commissioners didn’t see it that way. They ultimately decided to execute the elephant. Tip’s remains are still present at the American Museum of Natural History.
“Tip,” Braitman writes, “was deemed mad not because he was rabid or demonstrably insane but because he acted violently towards the men who sought to control him, keep him in chains.”
“[Tip’s] badness caused his madness, and his madness cemented his badness,” Braitman adds. “Tip was a victim of the human tendency to punish what we misunderstand or fear.”
Siracusa said he sees a somewhat similar dynamic playing out with some household pets that he interacts with. Pet owners who punish animals that show small signs of dysfunctional or unwanted behavior may actually be making the issue worse by fueling an animal’s early signs of anxiety. Siracusa compared this dynamic loosely to older generations of parents who hit children only to have that action manifest itself into aggressive or violent behavior later.
“I think this model, this way of interpreting dog behavior is still more prevalent than a more emotion-based interpretation of dog behavior even though there’s no solid scientific foundation for it,” Siracusa said.
Science takes animal emotions more seriously now
Attitudes around animal mental illness have changed over time. Pets like dogs and cats, long used primarily for “work” are increasingly considered part of the family. That more intimate connection means humans might pay more attention to signs of emotional disruption. A change has also occurred in the scientific community. Though prominent 19th-century observers of animals like Charles Darwin regularly commented on the supposed emotional states of creatures, Braitman says that practice became rarer 100 years later with the rise of prominent behavioralists like B.F. Skinner. Seeing human-like mental illnesses in animals became associated with anthropomorphism, a practice generally viewed as at odds with objective science.
“For a long time anthropomorphism was a dirty word in behavioral science,” Braitman writes.
But modern advances in brain scans and other more objective measures of understanding animal psychobiology continue to show more similarities. This has also contributed to newer waves of pharmaceutical-based treatments. A 2017 national pet survey by the research firm, Packaged Facts cited by The Washington Post, estimated that 8% of dog owners and 6% of cat owners gave medication to pets for anxiety or calming mood purposes. Clomicalm, Sileo, Anipryl, and a dog version of Prozac have all been prescribed to animals in recent years. Siracusa welcomed the use of these drugs in extreme cases but worried they may be being overprescribed. Quickly resorting to popular animal therapies like sedatives, Siracusa noted, might end up masking a problem rather than actually addressing it.
A greater awareness of animal mental illness by the general public could help cut down on unnecessary animal suffering. Siracusa advised prospective pet owners to first consider what they can do to prevent their animals from feeling distressed in the first place. Those who already have animals should also pay attention and never ignore early signs of anxiety forming. What begins as a minor compulsive oddity, he said, can evolve into destructive or possibly dangerous behavior over time. Siracusa said it’s also important to do research and not fall prey to the many misconceptions that exist about animals’ behavior. Maybe on the top of that list is the widely held idea that a dog’s wagging tail means they are happy. According to Siracusa, there’s not much evidence supporting that theory.
“I always tell my students, if you want to understand if someone is abused, don’t look at the butt, look at the face,” Siracusa said. “It’s the same thing for dogs. Why is everybody so fixated with the tail when the face of the animal is saying way more.”
This story is part of Popular Science’s Ask Us Anything series, where we answer your most outlandish, mind-burning questions, from the ordinary to the off-the-wall. Have something you’ve always wanted to know? Ask us.
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