The Racing Thought at Night

Moonlit Night at Miyanokoshi, from The Sixty-nine Stations of the Kisokaidō, ca. 1838 — Moonlit Night at Miyanokoshi, from The Sixty-nine Stations of the Kisokaidō, Utagawa Hiroshige, ca. 1838. The Metropolitan Museum of Art, Open Access (CC0).

One-forty at night. The thought runs a list: the email, the form, the appointment that has to be moved. It does not stop when told to. KTT counts it as a thought, noticed or not, even when it arrives as a body that will not settle. Research has looked at two answers people give to it, stop thinking and write it down. The studies read for this article did not test whether a thought comes first.

The instruction

The first answer is an order: stop. Daniel Wegner and colleagues tested it in 1987. Participants were asked not to think of a white bear for five minutes, then to think of it freely. The study is known for a rebound: after suppressing, people thought about the bear more than people who had never been told to suppress it. The rebound became a popular claim that trying not to think of something makes it return.

Later work is less certain. A 2001 meta-analysis of controlled studies found a small to moderate rebound that varied with the kind of thought and how it was measured. A 2020 meta-analysis of 31 studies found rebound effects whatever the mental load, and in a later paper nearly half of the rebound effects were reversed in direction. A recent study reports strong evidence against a rebound in its own task. So the rebound is real in the averages, modest, and not guaranteed. These were laboratory tasks with neutral thoughts, not a worry at one-forty.

The list

The second answer is a list. In 2018, Michael Scullin and colleagues had 57 healthy young adults, aged 18 to 30, spend a night in a sleep laboratory. Each person was randomly assigned to write either a to-do list or a list of completed activities for five minutes before bed. The to-do group fell asleep faster, in about 16 minutes against about 25, according to summaries of the study. The more specific the to-do list, the faster the sleep. For the completed-activities list, the trend ran the other way.

It was one night, and the participants were healthy. The authors say the findings may not apply to people with insomnia.

What is not known

Whether the thought comes before the restless body or after it is not known.

Whether a list helps outside a laboratory, over many nights, is open. Whether it helps with worries that are not tasks is also open.

Whether the instruction to stop makes things worse in real life is not settled either, given the mixed meta-analyses. Sleep that stays poor for weeks can call for professional care. This article describes thoughts, not treatment.