Efficacy of Docosahexaenoic Acid 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 To evaluate the clinical impact of DHA on the intensity of TD in humans. Study design Forty (40) subjects between 30-75 years of age will be recruited. The participants will be randomized and equally distributed in parallel groups to take either DHA (3 grams a day) or matching placebo capsules for 12 weeks, after providing informed consent. The study will use questionnaires, venous blood sampling, as well as clinical scales, to monitor the psychiatric condition, the lipid profile, and TD intensity at the beginning and end of the study. Brief and simple tasks will also be completed with a motion analysis system using magnetic sensors in order to measure body movements and TD with accuracy. Outcome The finding of a beneficial effect with DHA against TD would improve the quality of life for thousands of patients under long-term APD treatment.