Human research · Observational
Burns AC et al., Nature Mental Health 2023
Landmark T03 #1, main finding (revised against the author accepted manuscript; publisher version paywalled - accepted manuscript + free supplement + nature.com public back matter read). In 86,772 UK Biobank adults (aged 62.4 +/- 7.4 y, 57% women) who wore a wrist light sensor for one week, more night-time light was associated with HIGHER odds of most psychiatric outcomes and more daytime light with LOWER odds of several, after adjustment. The paper's PRIMARY model compares the brightest quartile (Q4) with the darkest (Q1) referent (Fig 2, Tables 2-3; fully adjusted Model 3: age, sex, ethnicity, photoperiod, employment, physical activity). Night-light Q4-vs-Q1 adjusted odds ratios (aOR): major depressive disorder 1.30 (95% CI 1.23-1.38), PTSD 1.34 (1.22-1.48), generalized anxiety disorder 1.23 (1.11-1.36), self-harm 1.27 (1.14-1.42), psychosis 1.21 (1.09-1.34); for BIPOLAR disorder the overall (omnibus) night-light test was NON-significant (omnibus chi2 P=0.18) and only the top quartile was elevated (1.20, 1.02-1.42) - so the abstract's listing of bipolar among night-light associations rests on the top quartile only. Day-light Q4 aOR: major depression 0.81 (0.76-0.87), psychosis 0.69 (0.61-0.79), self-harm 0.76 (0.67-0.87), PTSD 0.82 (0.73-0.92); day light was NOT associated with generalized anxiety (omnibus chi2 P=0.61) or bipolar disorder (omnibus chi2 P=0.22). This is a HUMAN CROSS-SECTIONAL (observational) study: lifetime psychiatric case status was compared with light measured on average 1.86 years EARLIER, so it shows ASSOCIATION, NOT causation - the authors state 'we acknowledge the possibility of reverse causation and that longitudinal studies will be needed to establish the temporality of the associations we observed.' The authors suggest 'avoiding light at night and seeking light during the day may be a simple and effective, non-pharmacological means of broadly improving mental health' - their interpretation, not demonstrated by this design. No medical advice.
Source: Day and night light exposure are associated with psychiatric disorders: an objective light study in >85,000 people. Burns AC, Windred DP, Rutter MK, Olivier P, Vetter C, Saxena R, Lane JM, Phillips AJK, Cain SW. Nature Mental Health 2023 (online 9 Oct 2023; issue Nov 2023, vol 1).
Verified research card EL-LM-T03-01-a-R3