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Gamma-linolenic acid for attention-deficit hyperactivity disorder: placebo-controlled comparison to D-amphetamine.

Arnold LE, Kleykamp D, Votolato NA, Taylor WA, Kontras SB and Tobin K (1989) Biol Psychiatry 25 222-228 

Web URL: View this and related abstracts via PubMed here


In a Latin-square double-crossover with random assignment to sequence, 18 boys, aged 6–12 years, with attention-deficit hyperactivity disorder received 1 month each of placebo, D-amphetamine, and Efamol (evening primrose oil containing gamma-linolenic acid, with vitamin E as preservative).

Parents' ratings were noncontributory. Teachers' ratings showed a trend of Efamol effect between placebo and D-amphetamine. The trend reached significance (p < 0.05) only on Conners Hyperactivity Factor.

Dosage may be crucial; 8 Efamol capsules per day were used in this study. Heuristic data scrutiny suggested possible interaction (sequence effect). Further study with a different design and dose is suggested. This study does not establish Efamol as an effective treatment.


In this small randomised controlled treatment trial, treatment with evening primrose oil (providing the omega-6 fatty acid GLA) was compared with both stimulant medication and placebo (dummy treatment). The aim was to assess the relative effects of each treatment on symptoms of attention-deficit / hyperactivity disorder (ADHD).

The participants were 18 boys with ADHD aged between 6 and 12 years. Each boy received each type of treatment for one month. (The order in which the three treatments were given was balanced across the group as a whole, but their order for each individual boy was decided by chance). Both teachers and parents provided ratings of each boy's ADHD symptoms before and after each monthly treatment period.

When the effects on ADHD symptoms of the three treatments were compared, no significant differences were found. (On teacher ratings only, stimulant medication was very slightly better than placebo.)

Closer inspection suggested that the order in which the treatments were given might have affected the results. The researchers suggested further studies using a different design and treatment doses.


This was one of the very earliest studies to investigate whether dietary supplementation with fatty acids might help to reduce symptoms of ADHD. In addition to the design limitations, the fatty acid treatment involved the omega-6 fatty acid GLA (from evening primrose oil).

Since then, attention has turned to the use of omega-3 fatty acids (notably EPA and DHA from from fish and seafood) rather than omega-6 for the treatment of ADHD and related conditions, although some trials have used a combination of the two. For reviews of these later studies, see:

Richardson, A.J. Long-chain polyunsaturated fatty acids in childhood developmental and psychiatric disorders. Lipids 2004 Dec;39:1215-22.

Richardson, A.J. Omega-3 fatty acids in ADHD and related neurodevelopmental disorders. Int Rev Psychiat, 2006, 18(2) 155-172.