Oméga-3 et psychiatrie : que dit la littérature ?

Psychiatry is faced with a lack of new treatments despite a great deal of research and is re-exploring the use of old molecules and dietary supplements. Our aim here is to present a narrative review of the indications for omega-3 supplementation in various psychiatric disorders. Omega-3s belong to the family of polyunsaturated fatty acids (PUFAs). The 3 important omega-3 PUFAs in psychiatry are α-linolenic acid (ALA): C18:3n-3, eicosapentaenoic acid (EPA) C20:5n-3 and docosahexaenoic acid (DHA) C22:6n-3. In psychosis, a distinction must be made between 3 categories of patients: patients who have chronic schizophrenia (SCZ), patients with a first psychotic episode (FEP) and patients at ultra-high risk of psychosis (UHR).

The data in the literature indicate that omega-3 supplementation is well tolerated. However, there is an increased risk of atrial fibrillation at doses over 4 g/d, mainly in people over the age of 65.

Omega-3 supplementation is not recommended for eating disorders, attention deficit hyperactivity disorder or autism spectrum disorders. Omega-3 supplementation could be beneficial in borderline personality disorder and psychotic disorders, particularly in patients at ultra-high risk of psychotic transition (UHR) to prevent psychotic transition and FEP to improve remission, and in bipolar disorder. It is now recommended for unipolar depression by the World Federation of Societies of Biological Psychiatry (WFSBP) and the Canadian Network for Mood and Anxiety Treatments (CANMAT) Taskforce. There are a large number of clinical trials of omega-3 supplementation. However, these trials use different types of supplementation (EPA alone, DHA alone, EPA + DHA, etc.) with different dosages and EPA/DHA ratios and over variable durations. In addition, the origin of the omega-3s may vary, although most of the studies used omega-3s of marine origin (fish). Finally, it has not been studied whether the time of day (fasting, during a meal, morning, evening, etc.) impacts the efficacy of the treatment.

Confounding factors are often not taken into account. For example, some studies suggest a link between the response to omega-3 supplementation and the inflammation or oxidative stress level. Omega-3 supplementation acts on numerous biological pathways: inflammation, oxidative stress, monocarbon metabolism (vitamin B9, B12, homocysteine), myelination,... For psychotic disorders, meta-analyses tend not to distinguish between UHR, PEP and schizophrenic patients.

There have not been enough studies to validate the doses and duration of supplementation. The doses and durations in the recommendations are based solely on incomplete data from published studies. Further studies are needed to optimize these recommendations. Except for UHR patients and those with borderline personality disorder, omega-3 supplementation is always used as a complement to psychotropic treatment.

In conclusion, the results of clinical trials, meta-analyses and recommendations are heterogeneous and may be divergent. Omega-3 supplementation in psychiatry is still extensively studied, with numerous studies and meta-analyses published recently. Omega-3 supplementation could be part of the goal of personalized medicine, as some studies are already suggesting. In the future, the efficacy of omega-3 supplementation could be improved by targeting sub-groups of patients: patients with inflammatory profiles, high levels of oxidative stress and low blood omega-3 concentrations. Due to the increasing number of studies published on omega-3 supplementation in psychiatric disorders, the conclusions of this review are provisional and will need to be updated.