Randomized, Double-blind, Placebo-controlled Trial on the Efficacy of Omega-3 Supplementation With Docosahexaenoic Acid (DHA) on Tardive Dyskinesia

Background

Tardive dyskinesia (TD) is a well-known complication of antipsychotic drug (APD) therapy in individuals treated for mental disorders such as schizophrenia. It typically consists of purposeless, involuntary movements involving the oro-facial area, trunk, and/or limb muscles, occurring within months or years of APD use. Twisting and protruding movements of the tongue, lip smacking and puckering, and chewing movements, are often observed. Oral dyskinesia may cause pain, traumatic lesions, tooth wear, impaired retention of prosthetic devices, chewing difficulty, dysphagia, speech impairment, as well as social embarrassment. The annual incidence of TD in the population treated with these drugs is between 1-5%, but the risk in older individuals is 5-fold greater. The second-generation ("atypical") APDs have substantially reduced the short-term risk of TD, but the annual incidence of TD in older individuals taking these drugs remains comparable to that of younger adults treated with first-generation APDs. The cause of TD is unknown. Since all APDs are blockers of dopamine D2 receptors in the brain, researchers hypothesized that these receptors (or their signaling pathways) become supersensitive in such a way to promote TD. APDs also modulate the expression of a number of brain factors belonging to the nuclear receptor family, including Retinoid X Receptors (RXR) and Nur77, which are overexpressed following chronic APD treatment. These factors, seemingly mounting an adaptive response to fend off adverse drug reactions such as TD, may become incompetent or insufficient over time in those individuals developing TD. One way to activate this response is to supplement the diet with high doses of essential fatty acids of the omega-3 class, which constitute a critical component of nerve cell membranes and modulate a variety of brain receptors. Once triggered, TD is often irreversible and untreatable. However, one team recently showed a 50% reduction in the severity of TD-like movements in mice treated with docosahexaenoic acid (DHA).

Hypothesis

Since there is an apparent close relationship between retinoid receptors and dopamine systems in the human brain and DHA is a RXR agonist, our working hypothesis is that DHA will reduce TD intensity in patients living with schizophrenia by increasing the transcriptional activity along these pathways.

Objective