Psychological Disorders in Animals: A Review of What We Know

An essay in BBC Earth summarizes what we know about mental illness in animals

Posted Sep 09, 2015

Almost four years ago, I wrote an essay called "Do Wild Animals Suffer From PTSD and Other Psychological Disorders?" in which I summarized much of what we knew then about PTSD and other psychological disorders in nonhuman animals (animals). I concluded, "Because wild animals don't get the medical care to which our companion animals are privy, those who suffer from extreme and debilitating psychological disorders simply die, as do those who suffer serious physical injuries and illness. So, my guess is yes, wild animals do indeed suffer from PTSD and other psychological disorders under natural conditions and that as time goes on we will learn more about the extent of these maladies. I encourage field workers to look for this and to report instances of psychological trauma. Even in the absence of a sufficient database, I can't imagine that the extent of psychopathologies among wild animals comes close to how rampant PTSD and other disorders are among captive animals whose lives have been highly compromised by humans by being forced to live in highly unnatural conditions in unnatural social groups." (For additional essays please see "PTSD in War Dogs Finally Getting the Attention It Deserves," "Captivity Drives Killer Whales Crazy: SeaWorld Fights Fines For Placing Profit Over Safety," and "Do Animals Worry and Lose Sleep When They're Troubled?")

I also wrote about the occurrence of psychological disorders in animals in Why Dogs Hump and Bees Get Depressed: The Fascinating Science of Animal Intelligence, Emotions, Friendship, and Conservation, and it seems now that more researchers are interested in mental illness in captive and wild animals and this week an essay by Shreya Dasgupta titled "Many animals can become mentally ill" was published in BBC Earth. Ms. Dasgupta summarized much of what we now know, including new data from neurobiological and genetic studies. Because her excellent essay is available online, here I'll provide some snippets to whet your appetite for more.

Ms. Dasgupta begins, "We have tended to think of psychological illnesses as a uniquely human trait. But that may be wrong. There is growing evidence that many animals can suffer from mental health disorders similar to those seen in humans. These unfortunate animals could help us understand how and why humans become mentally ill, and why these debilitating disorders ever evolved at all." She then notes, "It seems that animal mental illness can be triggered by many of the same factors that unleash mental illness in humans. That includes the loss of family or companions, loss of freedom, stress, trauma and abuse."

We also know, "Stressful events can even leave marks on animals' genes. In 2014, researchers found that African grey parrots that were housed alone suffered more genetic damage than parrots that were housed in pairs. The researchers examined the parrots' telomeres: caps on the ends of their chromosomes that slowly deteriorate with age or stress. 9-year-old parrots that were raised alone had telomeres as short as pair-housed birds that were 23 years older. It seems that social deprivation is stressful for parrots, just as it is for humans."

Ms. Dasgupta also writes about the genetics of psychological disorders, focusing on a family of synapse genes called Digstudied by Dr. Jess Nithianantharajah and her colleagues. It turns out that "Invertebrates – animals like flies and squid that lack backbones – have only one Dlg gene. But all vertebrates – backboned animals like fish, birds and apes – have four" and that "Mutations in these extra Dlg genes can give rise to many psychological disorders." Furthermore, "mice and humans with mutations in any of their Dlg genes had problems with various cognitive tests."

All animals can lose their minds

Further genetic studies showed that mammals other than humans possessed genes associated with schizophrenia and autism and "genetic studies like these [please see "Evolutionary conservation in genes underlying human psychiatric disorders"] do suggest that all animals with brains have the capacity to lose some aspects of their minds."

Ms. Dasgupta concludes, "But far from being something limited to pampered modern humans, mental illness can strike many kinds of animals and seems to have been around for hundreds of millions of years. Just like seemingly more physical disorders like cancer, it can be traced back to mechanical things such as genes and proteins within our cells. Mental disorders seem to be the price animals pay for their intelligence. The same genes that made us smart also predisposed us to madness. There's nothing shameful in that."

I'm thrilled there is so much interest in all aspects of the emotional lives of animals—the ups and the downs—and I highly recommend this fascinating essay and the links therein. There is no reason to assume we are unique in suffering from a wide variety of psychological disorders and I'm sure that future comparative research will show that we and other animals experience deep and rich emotions on both sides of the coin. 

Note: It's interesting that this essay immediately follows one called "Animals Don't Experience Emotions, Claims Texas Journalist" in which the writer ignores reams of hard data to the contrary and concludes, "There is no definitive scientific evidence that animals experience emotions as we do."

Marc Bekoff's latest books are Jasper's Story: Saving Moon Bears (with Jill Robinson), Ignoring Nature No More: The Case for Compassionate ConservationWhy Dogs Hump and Bees Get Depressed, and Rewilding Our Hearts: Building Pathways of Compassion and Coexistence. The Jane Effect: Celebrating Jane Goodall (edited with Dale Peterson) has recently been published. (; @MarcBekoff)