"The study shows that mood does get adjusted overnight," says Cartwright. "If you go to sleep in a bad mood, your brain goes to work right away on negative dream material at the beginning of the night so your bad mood is reduced by the end of the night." Next, Cartwright repeated the experiment using couples who were depressed by a recent marriage separation. While some unhappy patients dreamed less about serious emotional content and more about lighter topics as the night progressed, others had more disturbing dreams just before waking than at the beginning of sleep. Assuming that the former group was dreaming away their negative feelings each night, the researchers predicted that they would eventually work through their depression. And they were right - a follow-up study showed that 72% of the subjects in that group had fewer signs of depression one year later.