To date, there have been numerous case reports and drug monitoring studies with more than 5000 patients on the efficacy and safety of standardized St John's wort preparations.

• Depression A meta-analysis, published in the British Medical Journal by doctor K. Linde and colleagues, analyzed twenty-three randomized trials involving 1,757 patients suffering from mild to moderate depression. Dr. Linde found that in thirteen trials of hypericum versus a placebo, hypericum was vastly superior with a fifty-five percent improvement with hypericum versus a twenty-two percent improvement with the placebo.
  
  In three trials of hypericum versus standard antidepressants, both were found to be very similar but only twenty percent of the hypericum patients reported side effect whereas fifty-three percent reported adverse side effects with the standard antidepressants.
  
  These conclusions can be called into question, however since it is possible that negative studies were excluded from the meta-analysis. Also, the different studies cited in the meta-analysis used different herbal preparations and methods as well as different types of patients. Thus, limiting the validity of pooling together these results.
• Depression Dr. Ernst-Ulrich Vorbach and colleagues in Germany conducted a multi-center study of two hundred and nine severely depressed patients, of which thirty-eight were hospitalized at the time of the study. They used higher doses of hypericum (1,800mg opposed to the 900mg used in other studies) and compared the results to those obtained with imipramine, an old, standard tricyclic antidepressant. While the effects of the two treatments were very similar, there were far fewer side effects reported by those receiving hypericum - twenty-three percent versus forty-one percent of those on imipramine.
• Depression Dr. Helmut Woelk and colleagues in Germany monitored 3,250 patients being treated with hypericum by 633 private practitioners. The vast majority of these patients suffered from mild to moderate depression. In Dr. Woelk's study only 2.4% reported side effects and only 1.5% stopped treatment due to side effects. The most common side effects reported were gastrointestinal irritations, allergic reactions and restlessness - each occurring with a frequency of less than one percent
• Depression In eight different, controlled studies, scientists administered 300 - 1,000 mg, along with standard antidepressants. The antidepressant drugs caused 2.67 times the number of side effects that St. John's wort did. HIV: In test tube trials, St. John's wort has been proven extremely effective in the treatment of the HIV virus. However, clinical trials of people with HIV have been disappointing.
• Depression In a study in Austria, 67% of patients with mild to moderate depression improved when given an extract of St. John's wort.
• Tuberculosis Another study found that St. John's wort was effective in test tube experiments where extracts fought the bacterium that causes tuberculosis. So far, no results of clinical trials on tuberculosis have been released.
• Depression A recent analysis of 23 studies of St. John's wort concluded that the herb was as effective as antidepressant drugs - and more effective than a placebo - in the treatment of mild to moderate depression.
• Depression In one recent study, 50 participants with depression were given either St. John's wort or a placebo. After eight weeks, 70% of those on St. John's wort showed a marked improvement, versus 45% of those receiving placebo. No adverse reactions to the herb were noted.
• Depression Dr. Shrader found that St. John's wort was as effective as fluoxetine (Prozac®) in improving symptoms of mild to moderate depression in 240 people taking part in a randomized, double-blind study. Seventy two percent of people in the fluoxetine group reported side effects, compared with 28 percent of those taking St. John's wort.
• Depression In a double-blind study of 105 patients with mild-to-moderate depression, done by Dr. Harrer and Dr. Sommer in 1994, 67% responded favorably to treatment with St. John's wort extract, compared to only 28% of those on placebo. Significant improvements were noted in depressed mood, difficulty falling asleep, and feelings of fear.
• Depression A trial done in 1994 on 20 patients with seasonal affective disorder (SAD) showed St. John's wort to be as effective as phototherapy (light therapy) in improving symptoms of depression.
• Depression The National Institute for Health is currently conducting clinical trials on St. John's wort's antidepressant effects. Findings have not been released yet.