Polyunsaturated fatty acid supplementation for schizophrenia

Background

Limited evidence supports a hypothesis suggesting that the symptoms of schizophrenia may be the result of altered neuronal membrane structure and metabolism. The structure and metabolism is dependent on blood plasma levels of certain essential fatty acids and their metabolites.

Objectives

To assess the effects of polyunsaturated fatty acids for people with schizophrenia.

Search strategy

We have updated the initial searches of 1998, 2002 and 2005 with a search of the Cochrane Schizophrenia Group's Register, November 2008, which is based on regular searches of CINAHL, EMBASE, MEDLINE and PsycINFO.

Where necessary, we contacted authors and relevant pharmaceutical companies for additional information.

Selection criteria

We included all randomised controlled trials of polyunsaturated fatty acid treatment for schizophrenia.

Data collection and analysis

Working independently, we selected studies for quality assessment and extracted relevant data. We analysed on an intention-to-treat basis. Where possible and appropriate we calculated the Relative Risk (RR) and their 95% confidence intervals (CI) and estimated the number needed to treat (NNT). For continuous data we calculated weighted mean differences (WMD) and their 95% confidence intervals. We also inspected the data for heterogeneity.

Main results

Eight studies are now included in this review. When any dose omega-3 (E-EPA or EPA) is compared with placebo, small short trials suggest that the need for neuroleptics appears to be reduced for people allocated omega-3 supplementation (n=30, 1 RCT, RR 0.73 CI 0.54 to 1.00) and mental state may improve (n=30, 1 RCT, RR not gaining 25% change in PANSS scores 0.54 CI 0.30 to 0.96, NNT 3 CI 2 to 29). There are no differences in the number of people leaving the study early (n=595, 6 RCTs, RR 0.86 CI 0.50 to 1.48). There are few data on the comparison of any dose omega-6 (GLA) with placebo. For movement disorder outcomes, the one small study we found does not show any difference for average short-term endpoint AIMS score (n=16, 1 RCT, WMD 1.30 CI -1.96 to 4.56). When any dose omega-3 (E-EPA or EPA) is compared with any dose omega-3 (DHA) there is no significant difference for mental state outcome of not gaining 25% change in PANSS scores (n=31, 1 RCT, RR 0.66 CI 0.39 to 1.11). When different doses of omega-3 (E-EPA) are compared with placebo there are no differences in measures of global and mental state between the studies. For the outcome of 'experiencing at least one adverse effect' no differences between groups are found for any dose (1 g/day E-EPA vs placebo n=63, 1 RCT, RR 0.97 CI 0.60 to 1.56; 2 g/day E-EPA vs placebo n=63, 1 RCT, RR 0.67 CI 0.37 to 1.20; 4 g/day E-EPA vs placebo n=58, 1 RCT, RR 1.15 CI 0.72 to 1.82).

Authors' conclusions

Three updates of this review have resulted in more included studies and more people randomised but still relatively little useful additional data. The results remain inconclusive. The new trials all compare the omega-3 polyunsaturated fatty acids, in particular eicosapentaenoic acid and its ester, ethyl-eicosapentaenoic acid. The use of omega-3 polyunsaturated fatty acids for schizophrenia still remains experimental and this review highlights the need for large, well designed, conducted and reported studies.