Study Finds New Moms Have a Right to Be Cranky

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Waking up several times during the night is often the fate of insomniacs, on-call health workers, and, of course, parents of infants. Now, a new study suggests that "interrupted" sleep may affect people's mood more than getting very little sleep.

For a study published in the journal Sleep, researchers from the Johns Hopkins University School of Medicine had 62 healthy men and women spend three days and nights in a sleep lab. They were randomly assigned to three conditions: being woken up eight(!) times, being forced to stay up later but not woken up, or getting to sleep as they wished. Groups one and two got the same amount of total sleep. The participants filled out a mood questionnaire every night before bed.

After the first night, the interrupted-sleep and abbreviated-sleep groups had similar decreases in positive moods and increases in negative moods. But it was a different story after the second night: The forced-awakening people had a 31 percent lower positive moods while the short sleepers only had a 12 percent reduction.

The researchers also measured participants' brain waves as they slept and found, unsurprisingly, that the interrupted snoozers had shorter periods of restorative deep sleep than the late-bedtime group, which may explain the differences seen in demeanor. In addition to reducing positive mood and energy levels, interrupted sleep also lessened "feelings of sympathy and friendliness." As lead author Patrick Finan, Ph.D., told Time, "It’s not news that sleep problems alter people’s mood. But the granularity we measured here sheds new light on that relationship."

And this was only a three-day study. Hang in there, parents of adorable babies who are completely ruining your sleep.