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Are ω-3 fatty acids effective in improving the core features and associated symptoms of autism spectrum disorders (ASD)?
Improvements in ASD core features (social interaction, communication and stereotypy) on any scale. Secondary outcomes included improvements in aggression, hyperactivity, insomnia, self-injury and quality of life for individuals and families.
Systematic review and meta-analysis.
CENTRAL, MEDLINE, EMBASE, PsycINFO, BIOSIS, CINAHL, Science Citation Index, Social Science Citation Index and clinicaltrials.gov were searched up to 2 June 2010 and metaRegister of Controlled Trials and Dissertation Abstracts International searched up to 10 December 2008. Reference lists of retrieved articles and the internet were also searched, and authors of included trials contacted.
Study selection and analysis
Randomised controlled trials (RCT) of any type of ω-3 fatty acid supplement compared with placebo in people with ASD diagnosed using established diagnostic criteria or standardised instruments. The review meta-analysed continuous outcomes using fixed and random effects models, which gave similar results, therefore only the fixed effects results were presented. Heterogeneity was assessed using I2 and the χ2 test.
Two RCTs, involving 40 participants (37 competed the trials), met inclusion criteria. The 13 participants in one trial were all male and had a mean age of 10.5 years in the ω-3 group and 12.1 years in the placebo group. The other trial involved 24 boys and 3 girls with a mean age of 5.8 years. In both trials, the ω-3 was administered orally, at between 1.3 g/day and 1.5 g/day. Supplementation was given for between 6 and 12 weeks. Both trials evaluated outcomes using the Aberrant Behaviour Checklist (ABC), and scores on this scale were combined in the meta-analysis. There was no difference between ω-3 and placebo in social interaction (ABC social withdrawal/lethargy subscale: mean difference +0.82, 95% CI −2.84 to +4.48). There was also no difference in communication or stereotypy (ABC inappropriate speech subscale: mean difference +0.62, 95% CI −0.89 to +2.14; ABC stereotypy subscale: mean difference +0.77, 95% CI −0.69 to +2.22). The only prestated secondary outcome with data was hyperactivity; again there was no difference between ω-3 and placebo (ABC hyperactivity subscale: mean difference +3.46, 95% CI −0.79 to +7.70). There was also data for irritability, there was no difference between ω-3 and placebo for this outcome (ABC irritability subscale: mean difference −0.21, 95% CI −3.59 to +3.18).
The effectiveness of ω-3 fatty acids for ASD is unclear due to lack of large, high-quality trials. In the two small available trials, no statistically significant improvements in core or associated symptoms of ASD were observed with ω-3 supplementation over 6 to 12 weeks, compared with placebo.
James et al reviewed the efficacy of ω-3 fatty acids for improving the core features of the autism spectrum disorders (ASD) and associated symptoms. Their meta-analysis included studies reporting three primary outcomes, social interaction, communication, and stereotypy, and one secondary outcome, hyperactivity. Very few rigorous studies on the efficacy of ω-3 fatty acids have been conducted in ASD, and only two double-blind placebo-controlled pilot trials were included in this review, with a total of 37 participants.1 ,2 The treatment was well tolerated and resulted in no serious side effects. No statistically significant improvements were observed, and the largest positive effect for treatment was reported for hyperactivity. However, the opportunity to detect improvement in hyperactivity with treatment in one of the trials was limited by the fact that the study cohort had only mildly elevated levels of hyperactivity.2
It should be noted that small pilot studies are not designed to provide definitive scientific evidence regarding efficacy; their primary purpose is to prepare for larger studies. The review by James et al can therefore only be inconclusive. However, there are several reasons that larger studies are indicated. First, the observation that both trials found effect estimates in the same direction. Second, in the study by Bent et al,2 changes in hyperactivity were correlated with changes in certain fatty acids levels, suggesting a possible mechanism of action. Third, given that ω-3 fatty acids are taken by almost 30% of children with ASDs,3 this makes it imperative to determine their safety and efficacy in larger studies. Several randomised controlled trials of ω-3 fatty acids supplementation in ASD are currently ongoing or have been recently completed; together they will recruit more than 350 participants. These trials will help to determine if ω-3 supplementation is effective in ASD.
Sources of funding Not reported.
Competing interests None.
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