da Silva TM, Munhoz RP, Alvarez C, et al. Depression in Parkinson's disease: a double-blind, randomized, placebo-controlled pilot study of omega-3 fatty-acid supplementation. J Affect Dis. 2008;May 14. [Epub ahead of print] [PubMed]

Depression is the most common nonmotor symptom in Parkinson's disease (PD), affecting approximately half of all patients. Some researchers have postulated that depression may be linked to low levels of polyunsaturated fatty acids (PUFAs), raising the possibility that omega-3 PUFAs (as found in fish oil) might have a favorable impact. However, studies have thus far yielded contradictory results, documenting both positive and negative effects. Moreover, the potential relationship between PUFAs and depression in PD has not been explored. This issue was recently addressed in the first pilot study of omega-3 supplementation in patients with PD and major depression.

A total of 29 patients were randomized, in double-blind fashion, to take capsules containing either fish oil or mineral oil (placebo) for 12 weeks. Within each treatment group, some individuals were currently taking antidepressant medications and some were not. Scores on the Montgomery-Asberg Depression Rating Scale (MADRS), Beck Depression Inventory (BDI), and Clinical Global Impression (CGI) scale were comparable in the 2 treatment groups at baseline.

At the conclusion of the study, both MADRS and CGI scores were significantly improved with fish oil vs placebo among patients who were taking antidepressants, as well as among those who were not taking antidepressants (P<0.01 for both comparisons). A >50% reduction in the MADRS (which is considered clinically meaningful) was achieved by 42% of patients taking fish oil, as compared to 6% of those taking placebo (P=0.04). In addition, 22% of patients in the fish oil group fulfilled criteria for remission of depression (defined as a final MADRS score <12). The analysis of BDI scores did not reveal any significant between-treatment differences.

At the end of the study, patients who had been taking fish oil supplementation were followed for an additional 6 months. Some of the patients who had exhibited improvement while taking fish oil subsequently experienced reemergence of depressive symptoms after discontinuing the supplement.

The investigators cautioned that the results of this small study remain to be replicated in a larger-scale trial and cannot, at this point, be generalized to the entire PD population.