Winter Blues, Part 2: How Seasonal Depression Differs From Depression
Depression and Seasonal Affective Disorder have many symptoms in common. Both can involve a loss of interest in activities, poor concentration, disturbance in appetite and sleep, and suicidal thinking. However, there are several distinctions. The most obvious is that S.A.D. comes and goes with the changing of the seasons. While S.A.D. has been known to occur during the summer months, patients typically experience it in the winter months and find relief in the summer. In addition, the quality of the symptoms is S.A.D. often differ from a depressive disorder. For instance, people with S.A.D. tend to eat and sleep more than usual. This contrasts with depression where people are just as likely to eat or sleep less than they normally would. Researchers have noted for many years that one of the associated features of depression is the "overgenerality effect". Psychologists and clinicians have been using the concept of overgeneralization for decades. Psychotherapists often focus on this cognitive distortion with their depressed patients. Overgeneralizing involves taking an isolated event and then, with little evidence, drawing a general conclusion about yourself that spans many contexts and circumstances. For instance, one disrespectful experience with a sales clerk leads you to believe that no one respects you and that you are not worthy of respect. When you overgeneralize, aspects of the situation, for instance, that the sales clerks boss had just finished disciplining him or her, are not properly assessed. It is easy to see how this kind of cognitive distortion can lead to depressive feelings.
Researchers have studied the overgeneralizability effect within the context of autobiographical memory. What they have found is that, in response to positive and negative word cues (e.g., happy, jealous), people who are depressed tend to remember their past experiences in general, decontextualized terms. For instance, someone who is depressed may say, "I'm happy from time to time", whereas someone who is not depressed is more likely to say, "I remember going on my honeymoon with my wife. It was her birthday during the same time and we went out for a wonderful diner.” Research over the years has pointed to the fact that people experiencing depression fail to recall the contextual details that would confirm or provide evidence against their distorted thinking.
In 2001, researcher Tim Dalgleish and his colleagues conducted a study to determine if this overgeneralization effect was evident amongst people with seasonal affective disorder. As in previous research, they followed a group of patients experiencing S.A.D. What they found was that the overgeneralization effect was not evident in the experience of S.A.D. That is, people with S.A.D. were not overgeneralizing from their experience in the same way depressed patients would. The results provided evidence for the notion that S.A.D. is a biologically driven mood disorder caused by a lack of sunlight over the winter months and not caused by cognitive distortions such as overgeneralization. The results have implications for treatment. Some believe that the study provides evidence that medically based treatments, as opposed to psychotherapy, are indicated for this disorder. Medically based treatments for S.A.D. can include light therapy, medication, or even supplements of the hormone melatonin.
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