November 2001

Melatonin appears to be effective in the short-term treatment of tardive dyskinesia (TD) in schizophrenic patients, claims a team from Israel. However, they stress that further research needs to be done to determine whether the antioxidant is able to reverse the neuropathologic condition.

TD is estimated to occur in 3-5% of patients treated with antipsychotics during the first five years of treatment and 68% after 20–25 years of exposure to these drugs.

After six weeks, the researchers found that patients taking melatonin had a greater decrease in Abnormal Involuntary Movement Scale scores than patients in the placebo group. Moreover, no adverse events or side effects were reported.

Shamir's team comments that these results were similar to those attained with vitamin E over the same time period in a previous study. However, the significance of vitamin E treatment versus placebo was not unequivocally demonstrated. They point out that this could be due to melatonin being 6 to 10 times more effective as an antioxidant compared with vitamin E.

'In addition, melatonin enhances the expression of glial cell line-derived neurotrophic factor, a growth factor preferentially selective for dopamine neurons,' the researchers explain. 'Such neuroprotective mechanisms may be relevant to the anti-TD effect of melatonin.'

Despite the need for further investigation to determine the long-term efficacy of melatonin, Shamir et al conclude that 'melatonin treatment is beneficial for antipsychotic-induced TD'.

The research is published in the Archives of General Psychiatry.

Arch Gen Psychiatry 2001; 58: 1049–1052