TUESDAY, June 7 (HealthDay News) -- A new study suggests that depressed people suffer from an inability to rid themselves of negative thoughts because they can't turn their attention to other things.

"They basically get stuck in a mindset where they relive what happened to them over and over again," said study co-author Jutta Joormann of the University of Miami in an Association for Psychological Science news release. "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."

The study authors gave tests designed to gauge mental flexibility to 26 depressed people and 27 people who had never been depressed. They looked at words on a screen for one second each and then were told to remember them in forward or backward order. Then they were asked to look at individual words and say where they were in the original order.

Depressed people had a harder time with the task, especially if the 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 said.

Those who performed the worst also tended to ruminate on their problems.

The study appears in the journal Psychological Science.

More information

For more on depression, try the U.S. National Library of Medicine.