Melatonin is an important hormone in the sleep-wake cycle and in the timing of circadian rhythms. Melatonin secretion rates decline with age and this may be the cause of the change in body clock that occurs with increasing age. Melatonin supplements have been shown to reset the circadian rhythms where disturbances exist, and this may be useful in the treatment of certain types of depression. In seasonally affected disorder (SAD), often called winter depression, there appears to be a desynchronisation of the sleep-wake cycle, and in this regard melatonin supplements, or bright light therapy can be useful. However, there are other strategies that appear to be beneficial in the resetting of the sleep-wake cycle, and the herb Vitex agnus castus (chaste tree) might be particularly useful. Vitex agnus castus is a herb that has traditionally been used to treat menstrual disturbances, lactation problems and decreased labido. The use of Vitex agnus castus to improve sleep may result from its ability to increase melatonin secretion.
One type of anxiety and depression that may be particularly treatable by Vitex agnus castus is that relating to the pre-menstrual syndrome. The pre-menstrual syndrome is a complex condition, characterised by psychological changes that includes irritability, aggression, tension, anxiety and depression. One study treated patients daily with 20 mg Vitex agnus castus during three menstrual cycles. The results showed that those subjects taking the Vitex agnus castus extract had a significant reduction in their symptoms. In addition, when the subjects stopped taking the Vitex agnus castus extract, the symptoms slowly returned although there was still an improvement over the original levels. Of the 43 patients that took the Vitex agnus castus, 20 were considered responders, and they obtain reductions in their scores for pre-menstrual syndrome symptoms of at least 50 %. There were no serious adverse effects reported by the women in the study, and the Vitex agnus castus was well tolerated.
For example, in one study, researchers assessed the effects of Vitex agnus castus on the circadian rhythms of 20 healthy male volunteers. The volunteers received either a placebo tablet or a dose of Vitex agnus castus that varied between 120 and 480 mg per day for 14 days. Following this time there was a significant increase in melatonin secretion in the subject taking Vitex agnus castus, when compared to those taking the placebo. This response was greatest in those taking the most Vitex agnus castus. However, the circadian rhythms of the subjects were not affected. This lack of effect on the circadian rhythm may relate to the fact that they were healthy and did not have any problems with melatonin secretion. Therefore Vitex agnus castus may have some benefits with regard improving the quality of sleep through the secretion of melatonin. As this was evidence in healthy individuals, the effects may be more apparent in those with disturbed sleep patterns, such as those with anxiety and depression.
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