Interestingly, the earliest systematic 20th-century study of the effects of St John’s Wort on depression was inspired by the observation that Hypericum is a light-sensitive substance and that rats given Hypericum and then placed in bright light appeared to become more activated. To date there is only one study on the use of St John’s Wort in SAD patients. In this study, Dr Siegfried Kasper’s group in Vienna compared two groups of 10 SAD patients, one exposed to bright light in the morning for two hours a day for four weeks and one to much dimmer light for the same amount of time. Both groups received St John’s Wort 900 mg per day, and both groups responded very well over the four-week interval.
Given the way in which the study was designed, it is difficult to draw definite conclusions from it. Because there was no placebo group, the evidence for a specific effect for St John’s Wort was not completely clear-cut. Nevertheless, the anti-depressant results of St John’s Wort were promising. In addition, light therapy enhances the effects of the anti-depressant and the antidepressant cuts down the amount of time needed in front of the light box. There is no reason to suppose that the same beneficial interaction will not occur when it comes to the use of St John’s Wort. In my opinion, Sarah’s happy experience with using these two treatments in conjunction will prove to be the norm.
There are different ways in which light therapy and St John’s Wort can be combined. You could reason that since light therapy is the more established of the two treatments for SAD, it would make sense to begin to use light treatment as you enter the usual season of risk. As soon as it feels as though the light therapy is not fully doing the job, you could then add St John’s Wort. Another approach would be to start with St John’s Wort and add in light therapy only if it is necessary.
Although Kasper’s group found no harmful effects to the eye after four weeks of light therapy used in conjunction with St John’s Wort, there is a theoretical concern that the light-sensitizing effects of the herbal anti-depressant may produce harmful effects to the eyes over the long haul. Since such speculations by definition involve watching people over long periods, it will not be possible to answer them definitively for years to come. Even so, it is good to be aware of this possible interaction and to use less light if you are also taking St John’s Wort than you would if you were only using the light treatment. This should be easily managed as you will be benefiting from two remedies rather than just one. In addition, we have a natural inclination to do with as little light therapy as is needed to obtain an anti-depressant response.
One tip worth bearing in mind whenever you use an antidepressant to treat SAD or the winter blues is that the dosage needed usually varies depending on the season. For example, 300 to 600 mg of St John’s Wort might be sufficient in the autumn and spring, but larger doses may be necessary to combat the more severe symptoms that may occur in the depths of winter.
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