Limits of Clinical Investigations: What Clinical Research Can and Can't Do

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  • 0:06 Clinical Research
  • 1:10 Generalizability
  • 3:00 Proving Causation
  • 4:41 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.

How do psychologists figure out the causes of and best treatments for psychological disorders? In this lesson, we'll look at some limitations of clinical research, including the difficulty of generalizing research findings and proving causation.

Clinical Research

Tommy is a psychologist who wants to know about obsessive-compulsive disorder, or OCD for short. He knows that OCD involves anxiety, obsessive thoughts and compulsive behaviors. But, what causes OCD? And, what's the best treatment?

Abnormal psychology studies abnormal thoughts, behaviors and feelings. These abnormal thoughts, behaviors and feelings are often divided into psychological disorders, like OCD. In order to study psychological disorders in detail and to figure out the best treatment for them, psychologists do clinical research, or studying the causes and best treatments for disorders.

Clinical research can give a lot of information about psychological disorders. Through clinical research, psychologists learn how disorders work and how to treat them most effectively and safely. But, there are limitations to clinical research, too. Let's take a closer look at two major limitations of clinical research: generalizability and proving causation.


Tommy wants to do research on the causes of OCD. He decides to start with a type of research called a case study, which looks in detail at one person's thoughts, feelings and behaviors, as well as his or her history and response to treatment.

Tommy does a case study on Carter, a man who suffers from OCD. Carter gets very anxious about time and always thinks that he's going to be late. The only thing that relieves his anxiety and keeps him from having panic attacks is checking his watch every minute or so. When Tommy talks to Carter more in-depth, he discovers that Carter grew up in a house with a big grandfather clock close to the door. The clock would chime at regular intervals, and even when he was sleeping, Carter could hear the clock in his dreams.

From his case study of Carter, Tommy draws some conclusions:

  1. OCD patients are obsessed with time
  2. OCD patients check their watch compulsively
  3. Kids with grandfather clocks in their home will grow up to have OCD

Sounds pretty reasonable, right? This is what the case study has shown Tommy, so that must be what's true. The problem with Tommy's conclusions is that he is taking a specific case and generalizing it to apply to many different people.

Whether it's a case study or an experimental study that includes many people, being able to generalize the results of the study to a larger population is a key goal of research. But, it doesn't always work to make general statements based on specific examples, as we saw with Tommy's conclusions about OCD based on his case study of Carter. Instead, some clinical research leads psychologists to draw conclusions that are not valid because they do not apply to the general public.

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