A year after entering the study, 11 of the 40 teens treated only with placebo pills developed a psychotic disorder. This happened to only two of 41 teens who began the year with 12 weeks of fish oil capsules rich in omega-3 fatty acids.
No other intervention, including psychiatric drugs, has achieved as much for so long after treatment stopped. Moreover, antipsychotic drugs tend to have serious side effects, including weight gain and sexual dysfunction. Fish oil pills have no serious side effects.
The study suggests that to prevent one case of psychosis, four high-risk young people must be treated. That's the same level of efficacy seen with antipsychotic medications, note study researcher G. Paul Amminger, MD, of the University of Vienna, Austria, and colleagues.
"The finding that treatment with a natural substance may prevent or at least delay the onset of psychotic disorder gives hope that there may be alternatives to antipsychotics for the prodromal phase [symptoms leading up to psychosis onset]," Amminger and colleagues suggest.
Earlier studies have suggested that omega-3 fatty acids can alleviate clinical depression and other psychiatric disorders, although there have been mixed results.
It's not clear whether the fish oil pills help people with established psychosis. Despite having worrisome symptoms, none of the teens in the Amminger study had ever had a full-blown psychosis.
It's also not clear how fish oil might prevent psychiatric disorders.
Amminger and colleagues note that people with schizophrenia tend to have low levels of omega-3 fatty acids, suggesting that the mental illness could be linked to a defect in the ability to process fatty acids. There's also evidence that fatty acids interact with chemical signaling in the brain.
Particularly relevant to the Amminger findings is the suggestion that omega-3 fatty acids protect brain cells from oxidative stress.
Amminger and colleagues warn against over-interpretation of their findings. It may be that fish oil works better in young people with pre-psychotic conditions than in older people with more established psychiatric disorders. They do, however, strongly urge further research.
The study appears in the February issue of Archives of General Psychiatry.