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Chimps used in experiments show signs of post-traumatic stress and depression

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15 July 2011 in
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In humans, psychiatric conditions such as post-traumatic stress disorder and major depression, are commonly diagnosed after acute, repeated, or chronic trauma. Researchers have now shown that chimps can show behaviour indicating similar disorders following trauma such as being used in invasive experiments.


This is the latest research looking at the psychological effects of traumatic events on our closest living relatives.

It has been known for decades that captivity can cause pathological behaviours in nonhuman primates. For example, it is widely recognised that premature separation from mothers leads to a range of adverse behavioural and social effects in chimpanzee infants. Likewise, other unnatural rearing conditions, social isolation, prolonged captivity, sensory deprivation, and use in laboratory experimentation have been reported to contribute to abnormal behaviours in nonhuman primates. Such abnormal behaviours of chimpanzees and other nonhuman primates in captivity include repetitive stereotypic behaviour and self-injury.Just last week we reported on a new study showing that mental illness is endemic in chimpanzees kept in zoos.

In this latest research, the researchers used models for assessing post-traumatic stress disorder and major depression in humans to assess 196 chimpanzees living in wild sites in Africa and 168 chimpanzees living in sanctuaries with prior histories of experimentation, orphanage, illegal seizure, or violent human conflict

The study's lead author, Dr. Hope Ferdowsian, Director of Research Policy for the Physicians Committee for Responsible Medicine. “Chimpanzees are taken from their mothers at a very early age, sometimes just after they’re born," she says. "Chimpanzees are also forced into isolation many times as a result of being used in Hepatitis and other protocols. So there are clear harms associated with the use of chimpanzees in research, and we wanted to look at exactly how chimpanzees are affected by all the harms that are inflicted upon them over the course of a lifetime.”

In collecting their data, Ferdowsian and her colleagues relied on feedback from the chimps’ caretakers, who - in many cases - had known the animals for years.

One of the subjects was Negra, who spent 30 years as a test subject in biomedical research before being transferred to a chimp sanctuary. Negra's caretakers describe her as socially isolated and withdrawn, and she assumed a depressed, hunched posture, much like you’d see in humans with depression. “She walked around with a blanket over her head, really isolating herself from the rest of the world,” says Ferdowsian.

The researchers found that significantly more chimpanzees living in the sanctuaries (58%) met the criteria for depression than chimpanzees in the wild (3%), and more of the chimpanzees in sanctuaries (44%) also met the criteria for post-traumatic stress disorder than chimpanzees in the wild (0.5%).

The study concludes that the behavioral changes Negra and many other chimps exhibited after their laboratory experiences were very similar to those seen in combat veterans suffering post-rtraumatic stress disorder.

The researchers note that since nonhuman animals, including chimpanzees, are frequently used in research, there is an ethical imperative to understand the potentially adverse effects of captivity and their use in research: "Chimpanzees display behavioral clusters similar to PTSD and depression in their key diagnostic criteria, underscoring the importance of ethical considerations regarding the use of chimpanzees in experimentation and other captive settings."

Although chimpanzees are no longer used in experiments in the UK, they are also still used in experiments in some other countries. About 1,000 chimpanzees currently live in private and government-run laboratory facilities across the United States, where they are used as subjects for medical experiments. This new study focuses new attention on a proposed U.S. law, The Great Ape Protection and Cost Savings Act, which would phase out experiments on chimpanzees and retire the apes to sanctuaries.

OneKind is currently campaigning to maintain the UK’s welfare standards for animals used in experiments which are under threat. If you’ve not already done so please add your name in support of our campaign.

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