“Our results highlight the significant efficacy of LT, either as monotherapy or in combination with TSD, in the treatment of bipolar depression,” concluded a meta-analysis from 2016.Tseng et al., (2016). Light therapy in the treatment of patients with bipolar depression: A meta-analytic study. European Neuropsychopharmacology.
The results are not only scientifically significant, but also high enough for clinical application. The overall size of effect was 0.69 for the light therapy alone or in addition to other treatment. As an add-on therapy, the effect of bright light treatment had effect size of 0.51. These numbers are generally considered “moderate” – which means quite a lot in psychiatry and many well-known psychotherapies and pharmacotherapies also end up with effects labelled “moderate” rather than “large”.
To anyone who is into the lamps professionally, this is no news. But what I was really interested in were adverse effects. In major depression, light therapy is safe, except of very rare headaches or other minor complications, there it causes no differences. But for the bipolar patients, sometimes it was not really recommended because of possible switch from depression to hypomania or mania. What does the meta-analysis say about this?
Indeed, it mentions that this phase shift might happen. However, “the rate of phase switching was similar to that of antidepressant treatment, and the polarity shifting was temporary and could be immediately self-remitting or controlled by medication. No other significant adverse effects were noted during the course of light therapy course in the studies.”
Most of the studies involved were studying patients with bipolar disorder type I, which includes severe manias. Research still concludes that further studies are needed, because use of medication might have influenced some results – but in 2016, this was really great news. Now it is not so surprising, as two later analyses revealed in 2018 and 2019 that the mania switch is really not a problem at all.
Take-away message: Bipolar patients, welcome on board, effectiveness of bright light treatment for you is proven, too! And if you wonder which device to choose, a recent double-blind, controlled study proven this lamp to be efficient in bipolar depression: Carex Day-Light Classic Plus Bright Light Therapy Lamp.