Randomised trial, 1994
How does light therapy affect hormone levels in women with PMDD?
Light therapy shifted hormone timing in women with PMDD in different ways depending on the time of day. Women with PMDD had naturally higher prolactin levels throughout their cycle compared to women without PMDD.
What they did
RCT with 20 women with PMDD and 11 normal controls. Hormone levels (cortisol, prolactin, TSH, temperature) were measured during two menstrual cycle phases. Women received three light treatments in random order: bright white morning light (2500 lux, 6:30-8:30 AM), bright white evening light (2500 lux, 7-9 PM), or dim red evening light (less than 10 lux) for 1 week each.
What they found
In normal controls but not in women with PMDD, cortisol peak was delayed during the late luteal phase compared to the midfollicular phase. In PMDD, prolactin peaks and amplitude were higher, peaked earlier, and body temperature amplitude was higher during both cycle phases. After light treatment, prolactin remained higher in PMDD. Bright light shifted cortisol timing in both groups. Morning light increased prolactin nadir in both groups. Bright evening light increased TSH nadir in PMDD but decreased it in controls.
What it means for you
Women with PMDD have different hormone patterns than women without it throughout their cycle. Light exposure affects these hormones differently in PMDD versus normal women. The study measures hormones but does not clearly show whether these hormone changes improve symptoms. Very small sample sizes limit confidence in the findings.
20
women with PMDD
2500 lux
brightness of white light
1 week
duration of each light therapy
About the study
- Original title
- Neuroendocrine effects of light therapy in late luteal phase dysphoric disorder
- Authors
- Parry BL, Hauger R, Lin E et al.
- Journal
- Biological psychiatry
- Year
- 1994
- Study design
- Randomised trial
- What was tested
- Bright white light (morning or evening at 2500 lux) or dim red evening light (less than 10 lux) for 1 week
- Read the paper
- doi.org/10.1016/0006-3223(94)91210-6
Topics
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