Issues in Psychological Classifications: Reliability, Validity & Labeling

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  • 0:05 Classification
  • 1:29 Reliability Issues
  • 3:33 Validity Issues
  • 4:35 Lesson Summary
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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.

In order to help with diagnosis, psychologists classify mental disorders according to a group of symptoms. However, there are some problems with classification. In this lesson, we'll look at some of the common issues that arise with psychological classification.

Classification

Imagine that you are a psychologist who treats patients. One day, Leslie comes into your office. Leslie feels blue, feels tired all the time and isn't interested in hanging out with her friends or other things she usually enjoys. As Leslie's doctor, how do you go about treating her? Well, you could treat each symptom one by one, but wouldn't it make sense if you could figure out how to treat them all?

In the 19th century, Emil Kraepelin noticed that the way psychologists approached mental illness was neither efficient nor particularly good for the patients. He introduced the idea of classification - that is, grouping psychological disorders by common patterns of symptoms.

The idea behind classification is that there is not one symptom that appears only in one psychological disorder. For example, there's not a single symptom that is found in obsessive-compulsive disorder that's never found in another anxiety disorder. Instead, it is the unique pattern of symptoms that distinguishes obsessive-compulsive disorder from other anxiety disorders.

Since Kraepelin, classification has evolved. Today, the most commonly used classification system in the United States is found in the Diagnostic and Statistical Manual for Mental Disorders, or the DSM, which is put out by the American Psychiatric Association.

Reliability Issues

Classification of psychological disorders is obviously very useful. But there are several major problems with classification. One problem is that of reliability, or the idea that the classification system should give the same results every time you use it. For example, if I am using the DSM to diagnose Leslie today, and I come up with a diagnosis of a major depressive episode, then tomorrow the DSM should result in the same diagnosis for Leslie.

There are two types of reliability: inter-rater reliability and test-retest reliability. Inter-rater reliability is the idea that two people using the same classification system will come up with the same answer. For example, let's say that you and I both see Leslie. If we are both using the DSM to help us diagnose her, and we observe the same symptoms, then we should both come up with the same diagnosis.

Compare that to test-retest reliability, which is the idea that one person using the same classification system on another person should come up with the same diagnosis each time. For example, if I see Leslie and I use the DSM to diagnose her as having bipolar disorder, then if Leslie comes back tomorrow or next week with the same symptoms, I should also come up with bipolar disorder as the diagnosis.

So, how is this a problem? Classifications of mental illnesses have had some issues with reliability. Inter-rater reliability from one doctor to the next isn't always high because disorders overlap. For example, you and I might both agree that a patient has an anxiety disorder, but we may disagree on which anxiety disorder that patient has.

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