Summary of possible benefits and harms
Eight studies looked at how well omega-3 fatty acids worked to improve symptoms of schizophrenia. The studies did not include many people and did not last longer than 3 to 4 months. This means their results are not very reliable and don't tell us anything about any longer term effects.
The studies all looked at how well omega-3 fatty acid medicines worked compared with a dummy pill containing no active ingredient (also known as a placebo).
The results were mixed. Four out of the 8 studies showed that omega-3 fatty acids were slightly better than the dummy pills, leading to small improvements in some ratings scores that measure schizophrenia symptoms. However, the other 4 studies showed that omega-3 fatty acids were no better than the dummy pills at improving symptoms. This evidence therefore suggests omega-3 fatty acid medicines either don't work or may have small effects but, as mentioned, the evidence is not very reliable.
As with all medicines, there are some possible side effects, although not everyone gets them.
Omega-3 fatty acid medicines may increase the time it takes a person's blood to clot, which can be important in people with existing blood clotting problems or in situations where bleeding for longer than normal may be a problem, such as during surgery.
The most common side effects of using omega-3 fatty acid medicines are stomach problems and indigestion, and feeling sick. These occur in between 1 and 10 in every 100 people taking the medicine.
Results from the studies did not find any serious harm linked to omega-3 fatty acids when used for up to 4 months in people with schizophrenia. However, the possible harms or side effects of taking omega-3 fatty acids for longer than this in people with schizophrenia were not studied and so are not known.
Please note that the results of the research studies only indicate the benefits and harms for the population in those studies. It is not possible to predict what the benefits and harms will be for an individual patient being treated with omega-3 fatty acid medicines.