A reader asks:
I have several questions about medication for treating SAD. I have heard of agomelatine, a new (but not yet available) antidepressant that has effects on melatonergic receptors. Do you know of any benefit by this medication for treating SAD? Is there any evidence of a possible effect of taking serotonergic drugs for treating SAD? Is the pharma industry doing any research to create a drug specially designed for SAD?
Agomelatine is a promising new antidepressant being developed by Servier in Europe and Novartis in the USA. It is an oral melatonin receptor stimulator and a serotonin receptor blocker. Many experts think that its antidepressant effect is achieved primarily through its effects on serotonin receptors, but some think that the melatonin effect also contributes to the antidepressant effect. It has been shown to be effective in shifting circadian rhythms in humans and that might make it helpful for treatment of SAD, but this remains to be tested.
The evidence supporting the usefulness of serotonergic drugs (SSRIs) for SAD is very limited. Glaxo’s Wellbutrin XL (which has combined dopaminergic, serotonergic, and norepinephrine-receptor-blocking action), and is currently on the market, was approved by FDA in 2006 for the prevention of SAD. It was already on the market for the treatment of major depression (including SAD). All things considered, a drug that works for one kind of depression is likely to work for other types as well.
On the other side of the coin, the environmental therapies — light and negative air ionization — originally developed for treatment of SAD have now been shown also to work for non-seasonal depression. Indeed, recent clinical work shows that some patients (seasonal or non-seasonal) who have failed to respond to drugs — “medication-resistant” cases — respond well to light therapy. Finally, in cases of partial response to drugs or light therapy, their combination can be effective.