Light therapy for depression in pregnancy

Around 5-10% of women suffer depression during pregnancy (antepartum) and postnatal (postpartum) depression affects a further 10-15%. Both have been the subject of light therapy studies to alleviate depressive symtoms and some of the most interesting papers are summarised here.  

Antepartum depression

Antepartum depression severity is increased during seasonally longer nights: relationship to melatonin and cortisol timing and quantity.
Chronobiol Int. 2013 Nov;30(9):1160-73.
This study monitored 19 depressed and 12 non-depressed women through seasonal variations of light/dark, comparing mood depression scores, melatonin and cortisol concentrations. Mood scores worsened significantly in the depressed group and melatonin production started earlier (phase advanced) in the evening. Though there were no differences in cortisol production between the groups, high levels of cortisol corresponded to high depression ratings in the depressed group only. The authors suggest that "women who experience antepartum depression may be more susceptible... to phase alterations in melatonin and cortisol timing during seasonally longer nights. Interventions that phase delay - for example, increased exposure to bright evening light - might serve as an effective intervention." Read the full abstract

A randomized, double-blind, placebo-controlled study of light therapy for antepartum depression.
J Clin Psychiatry. 2011 Jul;72(7):986-93.
This research built on the results of the earlier studies. 27 women were exposed to bright white light - 7,000lux for one hour in the morning - over five weeks that improved depression during pregnancy week-by-week and significantly more than the placebo dim red light. "The study provides evidence that light therapy - a simple, cost-effective option with minimal side effects for the mother and no known risk for the unborn child - may be a useful nonpharmacologic approach in this difficult situation." Read the full abstract

Bright light therapy in pregnant women depression - 3 case studies.
Psychiatr Pol. 2006 Mar-Apr;40(2):261-7.
The women were in their 6th, 7th and 8th months of pregnancy and diagnosed with depression. Mon-Fri they were exposed to 1 hour of 5,000lux bright light therapy (BLT) and effects were assessed after the 2nd and 4th week. Depressive symptoms had improved by 33% after 2 weeks and by 55% after 4 weeks. It was noted that no side effects were observed and BLT required further study. Read the full abstract

Randomized clinical trial of bright light therapy for antepartum depression: preliminary findings.
J Clin Psychiatry. 2004 Mar;65(3):421-5.
Ten pregnant women with major depressive disorder were part of a 5-week clinical trial with either a 7,000lux light box or a 500lux placebo. At the end of the trial there was only a small positive difference for the bright light group. However, after a further five weeks treatment, the bright light therapy produced a significant improvement, similar to that seen in antidepressant drug trials. Read the full abstract

An open trial of morning light therapy for treatment of antepartum depression.
Am J Psychiatry. 2002 Apr;159(4):666-9.
After three weeks of bright light treatment, depression scores improved by 49%. Benefits were seen throughout the 5 weeks of treatment. 16 women took part and there was no evidence of adverse effects of light therapy on pregnancy. Read the full abstract

Postpartum depression

In theory, light therapy should be effective for postnatal depression too but there have been only a handful of studies, involving small numbers and the results have been mixed. For example, 15 women took part in this trial and there was a significant improvement over six weeks with light therapy... however, the placebo was just as effective.

Large scale trials with proper controls are necessary but it's probably not easy getting this patient group - depressed women that are also struggling with a new baby - to sign up for several weeks' research.