---
title: Does light therapy reduce depression symptoms before the period?
description: All light treatments reduced depression, but the placebo treatment also worked, so we cannot tell if bright light is specifically helpful.
url: https://niyora.com/research/papers/light-therapy-of-late-luteal-phase-dysphoric-disorder-an-extended-study-1993/
---

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- Does light therapy reduce depression symptoms before the period?

Non-randomised trial, 1993

# Does light therapy reduce depression symptoms before the period?

All light treatments reduced depression, but the placebo treatment also worked, so we cannot tell if bright light is specifically helpful.

 Moderate study design

19 women with late luteal phase dysphoric disorder and 11 healthy women

## What they did

19 women with late luteal phase dysphoric disorder and 11 healthy women tried three types of daily light for 1 week during the premenstrual phase: bright white light in the morning, bright white light in the evening, or placebo dim red light in the evening. They rotated through all three treatments over 3 months.

## What they found

All three light treatments, including the placebo dim red light, significantly reduced depressive ratings from baseline levels.

## What it means for you

Light may help mood symptoms before the period, but the strong placebo effect makes it unclear whether bright light itself is beneficial. The sample was small.

19

women with LLPDD

2500

lux of bright light

1

week of treatment

## About the study

Original title Light therapy of late luteal phase dysphoric disorder: an extended study Authors Parry BL, Mahan AM, Mostofi N et al. Journal The American journal of psychiatry Year 1993 Study design Non-randomised trial Participants 11 What was tested Bright white light (2500+ lux) or placebo dim light (<10 lux) daily for 1 week during premenstrual phase Read the paper [doi.org/10.1176/ajp.150.9.1417](https://doi.org/10.1176/ajp.150.9.1417)

## Topics

[Premenstrual syndrome (PMS)](https://niyora.com/research/topics/condition-pms/)[Premenstrual dysphoric disorder (PMDD)](https://niyora.com/research/topics/condition-pmdd/)[Low mood and depression](https://niyora.com/research/topics/symptom-depression-mood/)[Light therapy and sleep deprivation](https://niyora.com/research/topics/treatment-light-therapy/)[Major depressive disorder](https://niyora.com/research/topics/comorbidity-major-depression/)

Research tells you what helps on average. Niyora helps on the day it hits.

Calm down, see it another way, and decide what to say, with a PMS and PMDD app built by a doctor.

## Related studies

Randomised trial, 1999

Does bright light therapy help PMDD symptoms like depression and tension?

Study, 2010

Are women with PMDD more sensitive to how light affects sleep hormones?

Non-randomised trial, 2008

Does changing sleep timing help mood in women with PMDD?

Cohort study, 2026

What genetic factors are linked to premenstrual symptoms?

Systematic review, 2026

How often do mood disorders and PMS or PMDD occur together?

Review, 2024

What are the most effective treatments for PMDD?

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