International variations in the outcome of schizophrenia and the prevalence of depression in relation to national dietary practices: an ecological analysis

Background: Dietary variations are known to predict the prevalence of physical illnesses such as diabetes and heart disease but the possible influence of diet on mental health has been neglected.

Aims: To explore dietary predictors of the outcome of schizophrenia and the prevalence of depression.

Method: Ecological analysis of national dietary patterns in relation to international variations in outcome of schizophrenia and prevalence of depression.

Results: A higher national dietary intake of refined sugar and dairy products predicted a worse 2-year outcome of schizophrenia. A high national prevalence of depression was predicted by a low dietary intake of fish and seafood.

Conclusions: The dietary predictors of outcome of schizophrenia and prevalence of depression are similar to those that predict illnesses such as coronary heart disease and diabetes, which are more common in people with mental health problems and in which nutritional approaches are widely recommended. Dietary intervention studies are indicated in schizophrenia and depression.