Attention deficit hyperactivity disorder (ADHD) is characterized by problems with attention, hyperactivity and impulsivity. These problems often severely affect families, relationships and school performance. Although stimulants and atomoxetine are efficacious in many children, these medications can have side effects such as insomnia, decreased appetite, irritability and impaired growth. The etiology of ADHD is generally accepted to be complex and multifactorial. Little progress has been made in elucidating predisposing biological factors. Related contributory factors for ADHD etiology are diet, nutrition and particular abnormalities in the metabolism of the long-chain polyunsaturated fatty acids (LCPUFAs).
Essential fatty acids (EFAs) as a complementary or alternative treatment for ADHD have been used as both a primary and an adjunctive treatment in many countries. Humans are unable to synthesize linoleic acid (an omega-6 fatty acid), and a-linolenic acid (ALA), an omega- 3 fatty acid. The main dietary sources of linoleic acid and ALA are vegetable oils and their seeds.
Both omega-3 and omega-6 LCPUFAs have critical importance for normal brain development and function. Large amounts of both omega-6 and omega-3 LCPUFAs are deposited in the central nervous system during fetal life. During infancy, dietary intake of both omega-3 and omega-6 LCPUFAs continues to be essential for neuronal development. LCPUFAs and their derivates work as facilitators of dopamine, serotonin and norepinephrine release, as regulators of gene transcription, as modulators of Na+ -K+ ATPase channel function and as the precursors of pro-inşammatory and anti-inşammatory molecular families. The most abundant LCPUFA in the brain is DHA from the omega-3 series, which is concentrated at nerve cell synapses and is important for neural cell signalling and neurotransmitter processes.
There is increasing evidence that omega-3 LCPUFAs play a part in many neurodevelopmental and psychiatric disorders. ADHD, dyslexia, developmental coordination disorder and autistic spectrum disorder are suggested to be related to the omega-6/omega-3 spectrum of disturbances. Several studies of LCPUFA supplementation in children with ADHD symptoms have been conducted. Open-label EFA trials in ADHD demonstrate that ADHD symptoms are responsive to EFA supplementation. Despite successful open-label trials, randomized controlled trials of EFA in ADHD have generally been unsuccessful in demonstrating treatment effects and some of them even displayed better results for the placebo group. There are three studies with partial positive results but these studies represent a small minority and two of them have several methodological limitations.
The side effects of EFA are generally related to the gastrointestinal system and usually include diarrhea, nausea, fishy aftertaste, belching and indigestion. These side effects seem to be mild, transient and infrequent, and also appear in the placebo groups.
Current findings from randomized clinical trials of EFA in children with ADHD are not promising. Most randomized trials have clearly demonstrated lack of superiority compared to placebo. Moreover, the studies that showed positive findings did not use children properly diagnosed with ADHD and none of them demonstrated clinical improvement in more than one setting. This delineation does not support the use of EFA supplements as a treatment for children with ADHD. Future studies should be planned to consider methodological issues such as proper ADHD diagnosis, blinded controls, adequate sample size and behavioral assessment in more than one setting.