A sleepless night can leave the brain spinning with anxiety the next day.

In healthy adults, overnight sleep deprivation will trigger anxiety the next morning, along with altered brain activity patterns, scientists reported at the annual meeting of the Society for Neuroscience on Nov. 4.

People with anxiety disorders often have trouble sleeping. The new results uncover the reverse effect — that poor sleep can induce anxiety.

The study shows that “this is a two-way interaction,” said Clifford Saper, a sleep researcher at Harvard Medical School and Beth Israel Deaconess Medical Center in Boston who wasn’t involved in the study. “The sleep loss makes the anxiety worse, which in turn makes it harder to sleep.”

Sleep researchers Eti ­Ben ­Simon and Matthew Walker, both of the University of California at Berkeley, studied the anxiety levels of 18 healthy people. Following either a night of sleep or a night of staying awake, these people took anxiety tests the next morning. After sleep deprivation, anxiety levels in these healthy people were 30 percent higher than when they had slept.

On average, the anxiety scores reached levels seen in people with anxiety disorders, ­Ben ­Simon said in a news briefing on Nov. 5.

Sleep-deprived people’s brain activity also changed. In response to emotional videos, brain areas involved in emotions were more active. The prefrontal cortex, an area that can put the brakes on anxiety, was less active, functional MRI scans showed.

The results suggest that poor sleep “is more than just a symptom” of anxiety, but in some cases, may be a cause, Ben Simon said.