Randomised trial, 1997
Does light therapy affect melatonin in women with PMDD?
Bright light affected melatonin timing and levels in women with PMDD depending on when the light was given, with morning light shifting it earlier and evening light shifting it later. The evidence is moderate because it comes from a controlled study, but only 21 women with PMDD were studied.
What they did
Randomized crossover study. 21 women with PMDD and 11 normal controls had melatonin measured during the early and late cycle phases. They then received three types of light therapy in separate cycles: bright white morning light (6:30am to 8:30am), bright white evening light (7pm to 9pm), or dim red evening light (7pm to 9pm).
What they found
In PMDD women during the late cycle phase compared to the early phase, melatonin started later, lasted for a shorter time, and levels were lower. Morning bright light moved melatonin to start and end earlier and decreased duration and peak levels compared to red light. Evening bright light moved melatonin to start and end later and increased peak levels compared to red light, though duration still decreased. Normal control women showed different patterns.
What it means for you
Light therapy may help PMDD by changing melatonin timing and amount, but the sample was small and the study is from 1997. It is unclear whether changing melatonin actually improves mood or whether this is just one part of how light helps.
21
women with PMDD
11
normal control women
2,500 lux
brightness of bright light
About the study
- Original title
- Plasma melatonin circadian rhythms during the menstrual cycle and after light therapy in premenstrual dysphoric disorder and normal control subjects
- Authors
- Parry BL, Berga SL, Mostofi N et al.
- Journal
- Journal of biological rhythms
- Year
- 1997
- Study design
- Randomised trial
- Participants
- 21
- What was tested
- Bright white light in morning (6:30am to 8:30am), bright white light in evening (7pm to 9pm), or dim red light in evening
- Read the paper
- doi.org/10.1177/074873049701200107
Topics
Related studies
Randomised trial, 2023
Does a one-week sleep and light intervention help PMDD mood symptoms?
Cohort study, 2021
Do women with PMDD have worse sleep, focus, and tiredness problems that get worse before their period?
Randomised trial, 1994
How does light therapy affect hormone levels in women with PMDD?
Study, 2025
Could taking a combination of vitamins and minerals help with PMS and PMDD symptoms?
Review, 2024
Can sulpiride help women with both PMDD and IBS?
Study, 2011
Does bright morning light reset the body clock differently in women with PMDD?