Monday, January 11, 2016

Light therapy for non-seasonal depression

Lam et al. have published a study this month in JAMA Psychiatry  ( ) in which they show that people with non-seasonal major depressive disorder may have improvements in their mood with daily use of a light box alone.  Previously, light boxes have been used mainly in the treatment of seasonal depression or "SAD."

One of the reasons light therapy is attractive is that it is not a medication:  it is far less likely to cause side effect problems, and therefore it could have a much broader appeal, especially among people who are not comfortable using psychotropic medications.  

In the study, there were four groups:
1) 10 000 Lux light box exposure for 30 minutes as soon after waking as possible (the standard regimen of using light therapy), plus a placebo medication.
2) A "sham" or "placebo device" condition of sitting in front of a buzzing box (an inactive ion generator),  plus a placebo medication
3) 20 mg/day of fluoxetine +  placebo device
4) 20 mg/day fluoxetine + 10 000 Lux light box

The treatment duration was 8 weeks. 

 At the end of the study period, there were no significant differences between the fluoxetine+placebo device and the placebo medication+placebo device groups.   We could conclude from this that monotherapy with 20 mg/d of fluoxetine for 8 weeks had no benefit for treating major depression in this cohort! 

The light box+placebo medication group showed much more improvement (about twice as much change from baseline as the placebo-placebo group), with response rates typical for effective antidepressant therapies.   The combination group did best of all, with a response rate of 76% and a "remission rate" of 59%.

So this study supports the use of a light box alone as a viable therapy for depression, even if the depression does not have a seasonal pattern.
However, here are a few possibly cynical queries about this study:

1) while people in the study had to be medication-free for 2 weeks before the study commenced, I would suspect that many people in the study had tried other antidepressants.  This was not clearly documented.  By far the most common antidepressants that they would have tried would have been SSRIs.  Obviously, any SSRI trial would not have led to satisfactory improvement in these people, otherwise they wouldn't still be depressed!   In general there is not a lot of evidence that one SSRI is very different from any other, in terms of effectiveness.  Therefore, the study would have been biased against the medication group, in favour of the outcome which I presume the authors desired (which is to show that "light therapy is good").  If the authors wanted to control more powerfully for this factor, it would be necessary for them to assemble a cohort of depressed patients who had no prior history with antidepressants.

2) it is not hard to imagine that bright light could be a healthy, wholesome way to start the day.  It is much harder to imagine that sitting in front of a buzzing dark box could be beneficial.  The study demonstrated that the "expectancy scores" were the same for each of the four groups, i.e. that people in each of the 4 groups had a similar belief that the treatment they were receiving could be beneficial.   Yet, I question how compelling it would be for a modern person to believe that sitting in front of a buzzing box daily for 8 weeks would lead to a positive mood change or health benefit.

Furthermore, the treatments were absolutely not "blinded."  It would be obvious to the person sitting in front of the light box that they were receiving light therapy!  The person sitting in front of the buzzing box would be fully aware of not receiving light therapy!

3) people in the study were apparently told not to "spend an excessive or unusual amount of time outside" during the study!   If you are told not to go outside, do you not think that you might benefit even more from bright light indoors?   What if the effect of time outside exceeds the effect of the light box?!  In this case, how about prescribing that people just go outside for a half-hour in the morning after sunrise?   I'd be curious to see a study comparing a half hour walk outside with a half hour sitting in front of a light. 

Is a commercial 10 000 Lux light box really necessary?   How well can a person tell the difference between light intensities?    In various prior studies, the "sham" light therapy was a dim red light.  Here again, such a "device placebo" is not truly blinded!  Being stuck in front of a dim red light for half an hour sounds depressing just to think about!

The most interesting study I have come across looking at some of these questions was published by Riemersma-van der Lek et al in JAMA in 2008.
They had different lighting levels in nursing homes, followed for over a year.  People living in the homes could not guess accurately whether they were in the bright light condition or not (the intensities were approximately 1000 Lux vs 300 Lux, all day).  The brighter light seemed to cause some positive effects, and also eliminated negative effects caused by nightly melatonin administration.

To have a truly blinded study, we would need to use a light box of the same size, with the same colour of light, but with a lower intensity (for example, 5 000 Lux), but such that the person exposed to this light would not be able to guess the intensity level correctly.  That is, if you sat in front of the lower intensity light box, you wouldn't be able to tell that you were in the "dim light" group. This is reasonable to expect, since the visual system adjusts remarkably to different lighting conditions, causing wide ranges of measured illumination to be perceived similarly unless they are contrasted directly with each other at the same time. 

It would also be useful to more carefully assess the relationship, if any, between light therapy duration and intensity with clinical symptom changes.  What about 20 minutes vs. 30 minutes?  Or 7 000 Lux vs 10 000 Lux?   I suspect that the 10 000 Lux, 30 minute regimen is more arbitrary than one might expect. 

I have little doubt that bright light first thing in the morning is beneficial for mood--it seems like an obviously wholesome thing, which could also help regulate behaviour and sleep-wake patterns etc.  It could also be an opportunity to structure a type of meditative or study time in the morning.

But is a commercial product really necessary?  A typical "light box" costs about $200.  The electrical components inside are probably worth no more than perhaps $20-40.  It is just a fluorescent light!
It would be reasonable to conduct studies with "home made" light therapy, including just turning on a few extra lamps, or even just sitting in front of a bright east-facing window!  While the 30-minute treatment could be enjoyable and meditative for some, or a time to start the day with a bit of reading, it may be that the sedentary nature of light box exposure could be unhelpful for at least some people.  For these others, perhaps they could use that 30 minute time more healthily to get outside for a walk, instead of sitting in front of a box. 

One of the other applications for a light box that I have recommended to people is to help with morning sleep habits.  Many people have trouble waking and getting up out of bed at a regular hour (this regularity being a cornerstone of healthy sleep habits!).  Using a light box next to the bed, connected to a timer circuit which turns it on at the same hour each morning, could be used to help consolidate a regular sleep routine.  It would be like an "artificial sunrise."  (Of course, a natural sunrise would be much better still, but in our modern indoor world, it is hard to arrange this; also in a northerly latitude, the sun rises very late during the winter months, which is most likely a factor in causing seasonal mood and sleep changes).    So, using bright light as an "alarm clock" could be an idea worth trying, especially in the winter months. 

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