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Lying Awake Replaying the Day: What the Research Actually Shows
The honest headline is that the evidence is small and mixed. One study found that people who ruminated more after a stressful task took longer to fall asleep that night. Three small experiments then tested writing before bed. Two found people fell asleep faster, one found they did not, and the clearest result came from writing about what was still unfinished rather than replaying what was already done.
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What replaying does to falling asleep
A 2009 paper in Psychosomatic Medicine put people through an acute psychosocial stressor in a laboratory and then followed their sleep that night. Rumination was measured two ways: as a trait, before the stressor, and as the number of task-related thoughts people had during a 10-minute rest afterwards. Sleep was measured with a wrist actigraph and with each person's own estimate the next morning. Trait rumination predicted taking longer to fall asleep by the wrist measure, and rumination about the task predicted it by people's own estimates. The two also combined: the longest times to fall asleep were among people who were prone to rumination and who also kept thinking about the task. Neither kind of rumination was related to how long people slept or how much they woke in the night. The effect was on getting to sleep.
The sleep lab study: unfinished versus done
A 2018 paper in the Journal of Experimental Psychology: General tested what people write about, not just whether they write. Fifty-seven healthy adults aged 18 to 30 spent five minutes writing before a night of polysomnography in a controlled sleep laboratory. They were randomly assigned to write either a to-do list of tasks they needed to remember over the next few days, or a list of tasks they had completed over the previous few days. The to-do list group fell asleep significantly faster than the completed-list group. Detail mattered too. The more specifically people wrote their to-do list, the faster they fell asleep, while the opposite trend appeared for people who wrote about completed activities. That is worth sitting with if you lie awake replaying the day. In this study, going back over what had already happened was the condition that did worse.
Writing about worries: one result for, one against
Two earlier experiments tested a different kind of writing, modelled on James Pennebaker's expressive writing, where people write about their worries and feelings. In a 2003 pilot study in Behavioral Sleep Medicine, 42 poor sleepers were randomly allocated to one of three groups for three nights: writing about their problems, writing about hobbies, or no writing. The group that wrote about problems reported a shorter time to fall asleep than the group that did not write. A 2009 study in the same journal tried it with 28 people with insomnia, randomised to three nights of this writing or a control condition. Writing significantly reduced pre-sleep mental arousal on one of the two measures used, but it did not significantly reduce the time taken to fall asleep.
What this does not show
These are small studies: 57, 42 and 28 people. The 2003 study calls itself a pilot, and its result came from people's own reports of how long they took to fall asleep. The to-do list study was run in healthy young adults over a single night in a laboratory, not in people with insomnia and not at home over weeks. The rumination study shows that rumination predicted slower sleep onset. It does not show that stopping rumination would fix it. None of the studies tested speaking out loud or voice recording. All of them tested writing. We read each paper through its published summary, which gives no effect sizes, so we cannot say how many minutes any of these differences amounted to. Nothing here is medical advice. Trouble sleeping that goes on for weeks is worth raising with a doctor.
What that means if you want to try it
The practical reading is narrow. If the day keeps replaying, the one experiment that measured sleep directly suggests pointing the last five minutes forward: list what is still open, and be specific about it, instead of going back over what is done. Phi's 60-second voice entries are one way to say what is still open before you put the phone down. That is a format, not a tested treatment: the studies above tested five minutes of handwriting, not voice journaling.
Sources
Zoccola, P. M., Dickerson, S. S., & Lam, S. (2009). Rumination predicts longer sleep onset latency after an acute psychosocial stressor. Psychosomatic Medicine.Scullin, M. K., Krueger, M. L., Ballard, H. K., Pruett, N., & Bliwise, D. L. (2018). The effects of bedtime writing on difficulty falling asleep: A polysomnographic study comparing to-do lists and completed activity lists. Journal of Experimental Psychology: General, 147(1), 139–146.Harvey, A. G., & Farrell, C. (2003). The efficacy of a Pennebaker-like writing intervention for poor sleepers. Behavioral Sleep Medicine, 1(2), 115–124.Mooney, P., Espie, C. A., & Broomfield, N. M. (2009). An experimental assessment of a Pennebaker writing intervention in primary insomnia. Behavioral Sleep Medicine, 7(2), 99–105.Say it out loud instead.
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