Untreated schizophrenia is a very dangerous disease for which there is effective treatment, and for this reason it is not ethical to perform studies that compare a hypothetical new treatment against placebo. Therefore, studies of natural treatments for schizophrenia have looked at their potential benefit for enhancing the effects of standard treatment (or minimizing its side effects). No natural treatments have been studied as sole therapy for schizophrenia.
Up until recently, all common medications used for schizophrenia fell into a class called
. These drugs are most effective for the "positive" symptoms of schizophrenia, such as hallucinations and delusions. (Such symptoms are called "positive" because they indicate the
of abnormal mental functions, rather than the
of normal mental functions.) In general, however, these medications are less helpful for the "negative" symptoms of schizophrenia, such as apathy, depression, and social withdrawal.
might be of benefit here. A clinical trial enrolled 22 participants who continued to experience negative symptoms of schizophrenia despite standard therapy.
crossover study, volunteers were randomly assigned to receive either 0.8 g of glycine per kg of body weight (about 60 g per day) or placebo for 6 weeks, along with their regular medications. The groups were then switched after a 2-week "wash-out" period during which they all received placebo.
Significant improvements (about 30%) in symptoms such as depression and apathy were seen with glycine when compared to placebo. Additionally, glycine appeared to reduce some of the side effects caused by the prescription drugs. Furthermore, the benefits apparently continued for another 8 weeks after glycine was discontinued.
No changes were seen in positive symptoms (for instance, hallucinations), but it isn’t possible to tell whether that is because these symptoms were already being controlled by prescription medications or whether glycine simply has no effect on that aspect of schizophrenia.
Four other small double-blind, placebo-controlled clinical trials of glycine together with standard drugs for schizophrenia (including the newer drugs olanzapine and risperidone) also found it to be helpful for negative symptoms.
However, one small double-blind, placebo-controlled trial (19 participants) suggests that adding glycine to the drug clozapine may not be a good idea.
In this study, glycine was found to reduce the benefits of clozapine without helping to relieve the participants' negative symptoms. Lack of benefit, although no actual harm, was seen in two other double-blind, placebo-controlled trials of glycine and clozapine.
Another recent study not specifically limited to clozapine also failed to find benefit with glycine.
Curiously, a natural substance (sarcosine) that
the action of glycine has also shown promise for schizophrenia.
For more information, including dosage and safety issues, see the full