We all have our ups and downs—a fight with a friend, a divorce, the loss of a parent. But most of us get over it. Only some go on to develop major depression. Now, a new study, which will be published in an upcoming issue of Psychological Science, a journal of the Association for Psychological Science, suggests part of the reason may be that people with depression get stuck on bad thoughts because they’re unable to turn their attention away.
People who don’t recover from negative events seem to keep going over their troubles. “They basically get stuck in a mindset where they relive what happened to them over and over again,” says Jutta Joormann, of the University of Miami. She co wrote the new study with Sara Levens and Ian H. Gotlib of Stanford University. “Even though they think, oh, it’s not helpful, I should stop thinking about this, I should get on with my life—they can’t stop doing it,” she says. She and her colleagues thought people with depression might have a problem with working memory. Working memory isn’t just about remembering a shopping list or doing multiplication in your head; it’s about what thoughts you keep active in your mind. So, Joormann thought, maybe people who get stuck on negative thoughts have problems turning their mind to a new topic.
Joormann and her colleagues recruited 26 people with depression and 27 people who had never had depression. Each person sat in front of a computer and was shown three words, one at a time for a second each. Then, they were told to remember the words either in the order they were presented or in backward order. The computer then presented one of the three words and they were supposed to respond as quickly as they could whether that word was first, second, or third in the list. The faster they were able to give a correct answer, the better they were at thinking flexibly.
People with depression had trouble re-ordering the words in their head; if they were asked to remember the words in reverse order, they took longer to give the correct answer. They had a particularly hard time if the three words had negative meanings, like “death” or “sadness.”
“The order of the words sort of gets stuck in their working memory, especially when the words are negative,” Joormann says. She also found that people who had more trouble with this are also more likely to ruminate on their troubles. She hopes that these findings point towards a way to help people with depression, by training them to turn their minds away from negative thoughts.