Hypericum as an antidepressant
by Paul Bergner
Medical Herbalism 7(1&2):8-9
St. Johnswort (Hypericum perforatum) is perhaps one of the best-tested herbs in the world according to the standards of modern clinical trials. It has been shown in more than twenty-five trials to be an effective antidepressant. Thirteen trials were conducted in 1993 alone. The more recent trials, since 1989, have been better designed; earlier trials used a combination of hypericum and valerian rather than hypericum alone. Some trials compared hypericum extracts to placebo, and other to antidepressant drugs such imipramine, a commonly prescribed tricyclic antidepressant. Hypericum also held up in clinical trials against diazepam, desipramine, amitriptyline, bromazepam, and maprotiline. Hypericum extracts were either more effective than placebo or as effective as the drugs in each of the trials, and with fewer side effects than the drugs. Side effects to antidepressant drugs are common. Thus hypericum is not the poor herbal cousin of pharmaceutical antidepressants, but can hold its own clinically.
Method of action not clear
For decades herbalists and herbal regulators have held that hypericin and related compounds in St Johnswort are the active ingredient for antidepressant effects, and that they act through inhibition of monoamine oxidase, a substance that regulates the levels of neurotransmitters in the brain. This is how a class of antidepressants called MAO-inhibitors work There is no longer a consensus opinion among scientists either that hypericin is the active constituent, or that MAO-inhibition accounts for the antidapressant effects of St Johnswort extracts. [We challenged the MAO-inhibition theory for St Johnswort in 1990 (MH1990:2(1);1-3) on the basis that the extracts do not produce the side effects associated with MAO inhibition, which can include potentially fatal hypertensive crisis.] Early extractions of hypericin used in lab tests were apparently contaminated by other St Johnswort constituents, and a subsequent study has shown that pure hypericin does not have MAO inhibiting effects. Likewise other scientists have proposed that the slight MAC) inhibiting effects of other constituents in St Johnswort are not sufficient to explain its clinical action. Other possible actions are suppression of the cytokine interleukin-6, which in turn modulates the release of the adrenal hormone cortisol. The extracts any also affect the receptor activity on the brain for the neurotransmitter serotonin.
effects are practically
non-existent in the scientific literature. In
the course of six
controlled studies involving 230 patients, only
one patient reported
non-specific gastric trouble during the trials.
warns against the possibility of
photosensitivity — easy sunburn — but
this did not appear in any of the clinical
trials which lasted from 2-8
the trials used 900 mg daily
of a standardized solid extract of hypericum,
and it is difficult to
translate into tincture or other use. The German
2-4 grams of the dried herb as a daily dose.
Some early clinical trials
used 3-4.5 ml (about 90-135 drops) of a mixture
of hypericum and
valerian. It takes 3-4 weeks for antidepressant
effects to become
apparent. A month’s supply at this dose would be
about 6 ounces of