An increasing amount of scientific evidence suggests that animals, from chimpanzees to coyotes to parrots, can suffer from the same mental illnesses as humans. Understanding the biology behind animal depression, OCD, and PTSD could provide insight into why people suffer from mental illness and how these conditions evolved. From BBC Earth:
In a 2011 study, scientists found signs of depression and post-traumatic stress disorder (PTSD) in chimpanzees that had been used in laboratory research, orphaned, trapped by snares, or been part of illegal trade.
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…
"All you can do with animals is to observe them," says (University of Mississippi neurogenetics researcher Eric) Vallender. "Imagine if you could study mental disorders in humans only by observing them. It would be really hard to tell what's going on in their brain."
Faced with these obstacles, scientists have begun looking at animals' genes.
"A lot of mental disorders can be quite different. But what we do know is that they have a very, very strong genetic component to them," says Jess Nithianantharajah of the Florey Institute of Neuroscience and Mental Health in Melbourne, Australia.
All mental disorders, from depression to schizophrenia, involve abnormal behaviours. Those behaviours are influenced by genes just like other behaviours.
So the idea is to identify genes that can cause abnormal behaviours in humans and other animals. By tracing the origins of these genes, we can trace the origins of mental disorders.