"There is nothing either good or bad, but thinking makes it so." — Hamlet, Act 2, scene 2.

These lines from Shakespeare summarize a key idea in psychological research into depression: The way that people think influences their perceptions of events and, thereby, their symptoms. The pessimist with a "glass half-empty" mindset is more likely to become depressed in response to the trials and tribulations of life compared to the optimist with a "glass half-full" mindset.

This idea is a central element of cognitive therapy approaches to depression, where a therapist helps the patient identify, and then examine, the evidence for and against individual negative thoughts. Over 30 years of research confirms that people with depression tend to have more negative thoughts—and that more negative thoughts make people sadder.

However, as well as the content of a particular thought—e.g., "I am a failure" (negative) or "I am a success" (positive)—research is increasingly indicating that the process and style of thinking is important. In particular, there is recognition that repeated dwelling on the self, mood, and difficulties, is a key aspect of thinking in depression.

This repeated dwelling or brooding is called depressive rumination, and how often it occurs differs between individuals. Rumination includes dwelling on a problem over and over again without getting anywhere, getting stuck thinking over why you feel depressed, repeatedly reviewing your failings and mistakes, and constantly judging and evaluating yourself. It can often take the form of "Why me?" type questions, such as "Why do I feel so bad?" "Why can't I do this?" "Why can't I get better?" "Why did he treat me that way?" More than simply having individual negative thoughts, rumination is a style of responding that involves getting trapped in a repetitive and prolonged chain of negative thoughts, typically surrounding a single (negative) theme.

In an extensive programme of research, Professor Susan Nolen-Hoeksema, now at Yale University, has shown that this response style is characteristic of—and often perpetuates—depression. For example, a large-scale community study found that individuals who reported ruminating more frequently—e.g., almost always thinking "Why do I have problems other people don't have?"—when feeling down, sad or depressed were more likely to have elevated symptoms of depression a year later than people who reported thinking these statements less often (Nolen-Hoeksema, 2000).

There is also good evidence that rumination worsens mood and promotes negative thinking: In experimental studies, encouraging people to ruminate by asking them to think about self-related topics—like how tired or alert they feel, or how sad or happy they feel—exacerbates any pre-existing sadness and makes thinking more negative.

Together, these convergent findings from experimental and longitudinal studies provide strong evidence that rumination may be an important contributor to the maintenance of depression. (Later studies have shown that measures of rumination taken in adolescent girls predict their depression up to 2.5 years later, indicating that rumination may also be a risk factor for the onset of depression.)

So it isn't only that merely making negative interpretations and judgements about a situation can render people vulnerable to depression. Rather, it is the tendency to think too much about one's depression, stress, and difficulties that poses an important risk factor. And this thinking seems to be what keeps the majority of people with depression depressed.

Effective therapies for depression need to break this chain of negative thoughts and this tendency to think too much about things, in addition to making thinking less negative. Although cognitive therapy is focused on doing the latter, its ability to do the former is not particularly well established—mainly because the effect of CBT on rumination has been little studied.

Clinical experience raises the possibility that just learning to spot and challenge an individual negative thought may not be a very effective means to stop rumination. From my own clinical practice, I have often observed that successfully challenging a single negative thought has little overall impact for people who ruminate, as that thought is almost always followed by a further stream of negative thoughts. It is like catching a single drop of water when being hit by a deluge.

Yet there is a paradox to be resolved with respect to rumination. Thinking a lot about personal difficulties, setbacks, and losses isn't necessarily a "bad" behavior. More often than not it is a normal and adaptive response. When any of us experience an unexpected setback—the end of a relationship, becoming unemployed—it is natural enough to try and make sense of what happened by thinking it through and looking at our options. Further, there is an extensive literature in psychology on the value of coming to terms with emotional events by repeatedly thinking these events through (a mental ability known as cognitive and emotional processing).

Initially, this literature seems at odds with the research on depressive rumination because it suggests that thinking about upsetting events can be helpful. The best example of this is grieving: Part of the process of accepting a loss involves thinking about and mourning the deceased person.

People are likely to think about difficult events that happen to them. Sometimes this seems to be helpful; at other times, too much of this thinking might increase the risk of becoming—or staying—depressed. Thus rather than asking whether repetitive thinking itself is helpful or unhelpful, the more pertinent question may be what factors determine whether repetitive thinking is helpful or unhelpful, and how does such thinking go wrong in depression?

We are beginning to get some answers to these questions, and this will be the topic of a future blog.

About the Author

Edward Watkins
Edward Watkins, Ph.D., is a Professor of Experimental and Applied Clinical Psychology at the University of Exeter.

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