In a first-of-its-kind study researchers from Tel Aviv University report that interrupted sleep can be as physically detrimental as no sleep at all.

In the study, published in the journal Sleep Medicine, researchers established a causal link between interrupted sleep patterns and compromised cognitive abilities, shortened attention spans, and negative moods. The researchers discovered that interrupted sleep is equivalent to no more than four consecutive hours of sleep.

The study was conducted on student volunteers at TAU’s School of Psychological Sciences. Their sleep patterns were monitored at home using wristwatch-like devices that detected when they were asleep and when they were awake.

The students slept a normal eight-hour night, then experienced a night in which they were awakened four times by phone calls and told to complete a short computer task before going back to sleep after 10-15 minutes of wakefulness. The students were asked each following morning to complete certain computer tasks to assess alertness and attention, as well as to fill out questionnaires to determine their mood.

The experiment showed a direct link between compromised attention, negative mood, and disrupted sleep — after only one night of frequent interruptions.

“Our study shows the impact of only one disrupted night,” said TAU professor Avi Sadeh. “But we know that these effects accumulate and therefore the functional price new parents — who awaken three to ten times a night for months on end — pay for common infant sleep disturbance is enormous. Besides the physical effects of interrupted sleep, parents often develop feelings of anger toward their infants and then feel guilty about these negative feelings.