Classification & Diagnosis of Psychological Disorders

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  • 0:01 Diagnosis
  • 1:29 Problems with Diagnosis
  • 3:01 DSM
  • 3:12 5 Axes
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Lesson Transcript
Instructor: Natalie Boyd

Natalie is a teacher and holds an MA in English Education and is in progress on her PhD in psychology.

How do you diagnose something that you can't see? That's the problem faced by psychologists. This lesson will show you the tool they use to help diagnose their patients.


When you go to the doctor with a fever and a sore throat, he'll talk to you, examine you, maybe listen to your breathing, and he'll use this information to figure out an explanation for your symptoms. This explanation is his diagnosis, which is the identification of a nature and cause of an illness. In other words, the doctor's diagnosis is what he thinks has gone wrong with you and why he thinks it's gone wrong. The doctor determines that your sore throat is infected (that's the 'what') and does a quick swab test to determine that it's caused by the bacteria strep (that's the 'why').

Diagnosis in psychology is the same thing. If you think about it, though, it can be a lot harder to figure out what's going on in someone's mind than what's going on in someone's body. You can describe to your doctor that your throat is sore and he can look at you and run tests to figure out why. If you're depressed or if you're suffering from hallucinations or delusions, your description of your own symptoms can be more difficult to follow and interpret, and there's no equivalent of a throat swab to test for depression.

There are some ways that psychologists can diagnose patients, though. Let's look closer at the diagnosis and classification of mental illness, and the book that makes it possible for psychologists to figure out what's wrong with patients.

Problems with Diagnosis

Over the years, psychologists have worked hard to figure out ways to improve diagnoses. Psychologist David Rosenhan suspected that psychiatric hospitals often gave patients the wrong diagnoses. To prove it, he decided to send in pseudopatients, or healthy people pretending to be mentally ill, to test the doctors and nurses in the hospitals. The pseudopatients (including Rosenhan himself) pretended to hear voices. Once admitted to the psychiatric hospital, though, they acted normal and said their symptoms had stopped.

So, you might think, 'well, if they were acting normal, then they must have been released, right?' That's where the story gets interesting. They were not released and were not identified as having faked their symptoms. Because they had said they had one symptom at the very beginning, they were considered to have a mental illness for the rest of their life.

Interestingly, the actual patients in the hospital were suspicious of the pseudopatients. It turned out that the patients were better at identifying pretenders than the staff!

After Rosenhan announced these rather embarrassing results, one prominent hospital asked him to send them some pseudopatients, confident that in their hospital, the pretenders would easily be identified. Following the challenge, the hospital identified 48 pseudopatients out of the next 195 people who were admitted. But Rosenhan hadn't actually sent anyone!


Experiments like Rosenhan's show how difficult it is to come up with a reliable scientific system of diagnosing mental illness. For this reason, the psychiatric community has a book that's used to identify mental illness, based on the symptoms that a patient presents with. The Diagnostic and Statistical Manual of Mental Disorders, known as the DSM, has been undergoing constant revision since its creation in 1952.

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