Treating insomnia online in 3,755 students cut paranoia and hallucinations with it
3,755 students with insomnia at 26 UK universities got digital CBT for insomnia or usual care. At ten weeks insomnia fell (d = 1.11), and paranoia (d = 0.19) and hallucinations (d = 0.24) fell with it. No adverse events were reported.
Well-supported by good-quality research. how we score evidence
Caveat on this rating: Usual care rather than an attention-matched control, single-blind, and a student sample with insomnia rather than a clinical psychosis population; the authors flag the generalisation question themselves. The mental-health effects are small in size even though they are precise. Retention at follow-up is not stated in the abstract.
If poor sleep helps cause mental health problems, then fixing sleep should help the problems. This trial tested that directly, at a scale no psychological trial had reached.
Significant findings
Freeman, Sheaves, Goodwin and colleagues ran the OASIS trial at 26 universities in the United Kingdom. Between March 2015 and February 2016, 3,755 students with insomnia were randomised to a digital course of cognitive behavioural therapy for insomnia (1,891) or usual care (1,864). The research team was masked. Outcomes were measured online at weeks 0, 3, 10 and 22.
At ten weeks, the end of therapy, the sleep course "reduced insomnia (adjusted difference 4·78, 95% CI 4·29 to 5·26, Cohen's d=1·11; p<0·0001), paranoia (-2·22, -2·98 to -1·45, Cohen's d=0·19; p<0·0001), and hallucinations (-1·58, -1·98 to -1·18, Cohen's d=0·24; p<0·0001)." The mediation analysis found that "insomnia was a mediator of change in paranoia and hallucinations": the mental health gains ran through the sleep gains. "No adverse events were reported."
The authors call it "the largest randomised controlled trial of a psychological intervention for a mental health problem" and say it "provides strong evidence that insomnia is a causal factor in the occurrence of psychotic experiences and other mental health problems."
The other direction
The insomnia effect was large. The effects on paranoia and hallucinations were small (0.19 and 0.24), real but modest. These were students with insomnia, not people with a psychotic illness, and the authors say so: "Whether the results generalise beyond a student population requires testing."
What this does not show
Usual care was the comparison, not a sham program, so expectation could contribute. The trial measured paranoid and hallucinatory experiences on questionnaires, not diagnoses.
Worth asking
Before anything else, how is my sleep, and has anyone asked?
Source
The effects of improving sleep on mental health (OASIS): a randomised controlled trial with mediation analysis — Freeman D, Sheaves B, Goodwin GM, Yu LM, Nickless A, Harrison PJ, Emsley R, Luik AI, Foster RG, Wadekar V, Hinds C, Gumley A, Jones R, Lightman S, Jones S, Bentall R, Kinderman P, Rowse G, Brugha T, Blagrove M, et al. (41 authors, Espie CA senior) (2017)
Top-tier peer-reviewed journal
Read the source: https://doi.org/10.1016/S2215-0366(17)30328-0
DOI: 10.1016/S2215-0366(17)30328-0
How this was scored
- Study design
- Randomised controlled trial
- Funding
- Independently funded
- Published in
- Top-tier peer-reviewed journal
- Sample size
- 3,755
- Preregistered
- Yes
- Conflicts disclosed
- not recorded
- Independent of proponent
- not recorded
- Retracted
- No
Read the full scoring rubric, including what it can't tell you.
Published September 24, 2026.
Questions
How strong is the evidence behind this?
veisund rates this source "strong evidence". Well-supported by good-quality research. It scores 84 out of 100 on our published rubric. One caveat travels with that badge: Usual care rather than an attention-matched control, single-blind, and a student sample with insomnia rather than a clinical psychosis population; the authors flag the generalisation question themselves. The mental-health effects are small in size even though they are precise. Retention at follow-up is not stated in the abstract. The score is calculated from recorded facts about the source — study design, funding, publication venue, sample size, preregistration — not typed in by an editor.
What is the source for this?
The effects of improving sleep on mental health (OASIS): a randomised controlled trial with mediation analysis — Freeman D, Sheaves B, Goodwin GM, Yu LM, Nickless A, Harrison PJ, Emsley R, Luik AI, Foster RG, Wadekar V, Hinds C, Gumley A, Jones R, Lightman S, Jones S, Bentall R, Kinderman P, Rowse G, Brugha T, Blagrove M, et al. (41 authors, Espie CA senior) (2017). Published in: Top-tier peer-reviewed journal. DOI: 10.1016/S2215-0366(17)30328-0. The full source is linked on this page so you can read it yourself.
Who paid for this research, and does that matter?
Study design: Randomised controlled trial. Funding: Independently funded. Independence from the proponent is not recorded. Industry sponsorship is one of the most reliably measured biases in medicine, which is why funding carries real weight in the score rather than sitting in a footnote.
Is this medical advice?
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.
This is information to bring to your prescriber, not medical advice and not a reason to change anything on your own. Nothing here is an instruction to stop or reduce a medication. If you are in crisis, call or text 988.