Why you don't need to be 'SAD' to benefit from light exposure

I saw an individual in practice yesterday, who told me she’d recently had a bout of low mood that was ‘out of character’ and not for any obvious reason. The issue started around mid-December last year, but had recently appeared to lift. The first thing that occurred is perhaps this lady was suffering from seasonal affective disorder (SAD) or something similar. It’s well known that as the winter draws in and the days get shorter, some people are prone to low mood precipitated, it seems, by lack of sunlight.

I mentioned this to her and she told me her sister had remarked that all she needed was ‘a holiday somewhere sunny in the winter.’ I remarked that perhaps her sister had a point. My patient remarked, quite rightly, that this is not always practical. However, getting more light in the winter doesn’t necessarily mean relocating to somewhere sunny. It could mean ‘buying in’ light in the form of a sunlight-simulating device. In 2009 I wrote about this and also quoted some evidence which suggests the light from the blue part of the visual spectrum appears to be most important for mood maintenance. For a more general review of some natural approaches that may combat SAD, see here.

While light therapy does appear to have potential in combating depression of a seasonal nature, there is some evidence that it might help combat non-seasonal depression too. In a study published recently in the Archives of General Psychiatry, blue light therapy was tested in a group of individuals aged 60 or over with ‘major depressive disorder’ [1]. The depression was non-seasonal in nature (in other words, it did not appear to be precipitated by lack of light in the winter).

Treatment consisted of bright blue light therapy (about 7500 lux where lux is a measure of light intensity) for an hour each morning. This was compared to a ‘control’ treatment of dim red light (about 50 lux) for the same time. Treatment was for a total of 3 weeks, and individuals were assessed for a following 3 weeks following treatment too.

Depression scores reduced significantly in the group receiving blue light compared to those getting the control treatment.

Sleep improved, and also individuals ended up getting out of bed sooner after waking in the morning.

Some biochemical parameters were also checked. Levels of the stress hormone cortisol came down considerably in the evening in response to bright blue light. And levels of melatonin (the chief neurochemical responsible for sleep) increased more rapidly after exposure to blue light too.

All in all, these results suggest that bright blue light therapy might have benefits for mood and sleep even in those who do not appear to be suffering from SAD per se. Another study, this one confined to women, also found that in blue light therapy improved mood and energy in individuals suffering from non-seasonal depression [2].

This evidence does support the notion that light has benefits for mood and general wellbeing, and may cause some of us to increase our efforts to get adequate light exposure throughout the year either in the form of sunlight and/or appropriate light device.

References:

1. Lieverse R, et al. Bright light treatment in elderly patients with nonseasonal major depressive disorder: a randomized placebo-controlled trial. Archives of General Psychiatry. 2011;68(1):61-70.

2. McEnany GW, et al. Effects of light therapy on sleep, mood, and temperature in women with nonseasonal major depression. Isses Ment Health nurs. 2005;(7):781-94.