Aaron Beck argues that dysfunctional patterns of thinking may lead to depression.  Beck noticed these patterns in his own clients and there are several correlational studies that link this type of thinking to depression.  However, correlational studies lead to the question of bidirectional ambiguity.  Do dysfunctional patterns of thinking lead to depression, or does depression lead to dysfunctional patterns of thinking.

Beck posited that dysfunctional thinking is a vulnerability factor for depression.  Joiner et al postulated that dysfunctional thinking should be associated with the development of depressive symptoms in the presence, but not the absence, of negative life events. In other words, they argued that the cognitive approach to depression is based on the diathesis-stress model – when one has negative thinking patterns and then is exposed to a life stressor, there is a higher probability to develop depression.  However, negative thinking alone does not lead to depression.

In order to test this hypothesis, Joiner carried out a prospective study of the role of exam stress in university students.

Joiner et al wanted to determine the role of depressive and anxious thinking patterns on the development of depressive symptoms.  They hypothesized that negative thinking patterns, but not anxious cognitions, would play a role in the onset of symptoms related to depression.

The sample was made of 119 American university students, all taking an abnormal psychology course. The mean age of the students was 19 years old.

The stressor that the researchers would observe was mid-term examinations.  The students were assessed two weeks before and two weeks after their mid-term examinations.  As the administration of the exams was naturally occurring in the university setting, this study was a natural experiment.

To assess the students, there were three tests that were given.

1. The Dysfunctional Attitudes Scale [DAS] This test measures thinking patterns such as vulnerability, need for approval, perfectionism and the need to impress.  This was taken only before the mid-term exams.
2. The Cognitive Checklist [CCL]. Half of the questions determine automatic thoughts linked to depression; the other half, linked to anxiety.  This test was taken both before and after the exams.
3. The Beck Depression Inventory [BDI]   A standardized assessment to measure levels of symptoms linked to depression.  This test was also taken both before and after the exams.

The researchers found an increase in the scores on the BDI only in students who had higher scores on the DAS and who had failed an exam.  Students who had a higher score on the DAS but did well on the exams showed no significant increase in their BDI score.   For the students who had lower scores on the DAS, even if they received low grades, they did not experience depressive reactions.

When looking at the scores for the CCL, there was a correlational between having higher scores on the depressive thinking patterns questions and the increase in the BDI scores if a student failed an exam.  There was no significant correlation between the anxiety scores and an increase in BDI scores.

The study was prospective, allowing the researchers to see change over time.  This allows researchers to control for bidirectional ambiguity.

The study was naturalistic, meaning that there was limited control over extraneous variables.

Although there was an increase in depressive symptoms, this is not the same as a clinical diagnosis of Major Depressive Disorder.  The experiment's results may not indicate what may happen in clinical depression.

There was a sampling bias.  The study was carried out on American undergraduates who were studying psychology. The age, culture and education of the sample may all have played a role in the results of the study.