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Helpless dogs looked depressed
Seeing depression
A professor named Jim Gear came to look at the helpless dogs and told a graduate student, Martin Seligman, that he was looking at depression. In 1970, unipolar depression was not a diagnostic category. By 1975, the American Psychiatric Association's diagnostic manual isolated it for the first time, with nine symptoms, and five present for two weeks or more earned the diagnosis.
The nine symptoms
The nine were passivity, cognitive difficulty, sadness, anxiety, trouble sleeping, food not tasting good, numbness, lack of mirth, and thoughts of death. The helplessness literature that had piled up by 1975 showed eight of them. Only thoughts of death were missing, probably because the experiments used things like loud noise.
From lab to drugs
Learned helplessness became the leading model of depression, and it opened up a neuroscience in which researchers tried drugs that broke up helplessness in rats and then tried them in people. The drugs that worked against helplessness in the laboratory became the leading antidepressants.
Why test antidepressants on rats?
In 1977, Roger Porsolt and colleagues in France described a test in which a rat or mouse is placed in a tank of water it cannot escape from. The animals eventually stop swimming and float. Antidepressant drugs reduced the time the animals spent floating. The forced swim test became widely used for screening drug candidates.
Why couldn't animals show thoughts of death?
Thoughts of death are inner experiences that people report in words. Animal experiments can measure only behavior, so researchers looked at things like failure to escape, weight loss, changes in sleep, and reduced appetite. The symptoms that match are the ones that can be observed from the outside, such as passivity, disrupted sleep, and loss of appetite.
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