Sleep and anxiety: the hours matter less than you think

Sleep and Anxiety: The Hours Matter Less Than You Think

Short sleep does track with more anxiety. But the newer genetic evidence points at insomnia itself, not at the number your sleep app hands you in the morning.

If you have ever lain in the dark doing arithmetic, five hours, maybe five and a half, you already know the loop. Bad sleep makes you edgy, and being edgy makes the next night worse. What the research has always struggled with is which way the arrow actually points. This year a few pieces of evidence lined up, and the answer is more useful than being told to get eight hours. The signal is not really in the hours at all. It sits in whether your nights are broken, and in whether short sleep has tipped over into something with a name.

KEY TAKEAWAY

Broken sleep, not simply short sleep, is what tracks most reliably with anxiety.

WHY IT HAPPENS

Sleep is partly where your nervous system rehearses letting go of a threat. In the lab that shows up as habituation: your heart stops dropping so sharply the third time you see an unsettling image, because your body has quietly filed it as harmless. A team at the University of L’Aquila interrupted volunteers’ REM sleep with gentle wrist vibrations, carefully enough that total sleep time and sleep efficiency did not change at all. The habituation disappeared anyway. Their bodies kept reacting to the same pictures as if each viewing were the first.

EVIDENCE

Across 13,476 US adults in the national NHANES survey, Xing Wang and colleagues (Psychology Research and Behavior Management, 2025) found that sleeping under five hours came with a 40 percent higher rate of anxiety symptoms. Sleeping nine hours or more showed no significant link once health and lifestyle were accounted for.

FIX 1

Ask whether it is short sleep or insomnia

The distinction is not academic. Using genetic data, Qingxing Lu’s team at Jilin University found insomnia raised the odds of an anxiety disorder by roughly 68 percent, while an earlier study using the same method found no causal link for sleep duration. The signal follows insomnia, not hours. If you routinely need over 30 minutes to fall asleep, or lie awake in the night, three or more nights a week for months, that is the thing to name.

FIX 2

Do not wait for the mood to lift first

Most people treat sleep as the thing that will sort itself out once life calms down. Yuki Furukawa’s team at the University of Tokyo pooled 19 trials and 4,808 people with depression and insomnia. Treating the insomnia lifted depression response from 17 percent to 32 percent, and the gains went beyond sleep itself. Worth knowing: these trials measured depression, not anxiety, so read it as a strong hint rather than proof.

FIX 3

Defend the last two hours of the night

REM is stacked into the final third of your night, which is exactly when a buzzing phone or a thirsty dog costs you the most. The L’Aquila work suggests you can lose that emotional recovery without losing a single hour of sleep. So the small interruptions matter: put the phone on do not disturb overnight, not just at bedtime, and deal with the 5am light leak at the edge of the curtain.

FIX 4

Stop grading yourself every morning

Here is the honest limitation of the NHANES finding: sleep and anxiety were each captured by a single self-reported question. People are poor judges of how long they slept, and anxious people tend to underestimate it. Which cuts both ways. A number that makes you brace for a terrible day is an input worth ignoring on the mornings you feel fine. Check in with your body before you check the app.

→ QUICK POLL

Does a broken night reliably make the next day feel more anxious for you?

YES

Sleep well,

Claire Ashton

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