Schizophrenia Daily News Blog

Diet May Affect Outcome of Schizophrenia

It is well known that diet affects a person's physical health and can lead to conditions such as diabetes and coronary heart disease. But can your diet affect your mental health as well? An article in the British Journal of Psychiatry suggests that it does. In order to asses international differences in the outcome of schizophrenia, the article reviewed evidence from the International Pilot Study of Schizophrenia (World Health Organization, 1979) and the Determinants of Outcome of Severe Mental Disorders study (Jablensky et al, 1992). Outcome was rated by the number of days spent in hospital and general social impairment. Dietary information correlating to the years of the studies was taken from the Food and Agricultural Organization database of apparent national food consumption. All of this data was then compared by statistical analysis.

The most consistent correlation found in this study, was that increased consumption of refined sugar results in an overall worse outcome for schizophrenia, as measured by both the number of days spent in the hospital and poor social functioning. This association was found in both databases used. Weaker correlations between increased intake and worsened outcome were found for alcohol, meat, and eggs. One study found that consumption of dairy products resulted in fewer days in the hospital but poorer overall outcome. A weak association was also found between consumption of pulses (pod-bearing plants like peas and beans) and improved outcome.

Previous studies have shown that insulin resistance and diabetes as well as heart disease occur with greater frequency in people with schizophrenia. Insulin resistance is increased by regularly high intake of sugar and saturated fats. How these factors affect a person’s physical condition and lead to diabetes or heart disease is well understood. How the same factors might affect the course of schizophrenia is much more uncertain territory. However, substances consumed in food can definitely affect the chemistry of the body and, subsequently, the functioning of the brain. An experiment done in 2002 showed that omega-3 fatty acids (found mostly in seafood) have strong antidepressant properties. Another experiment, done on rats, showed that a high-fat, refined sugar diet reduced levels of brain-derived neurotrophic factor, a molecule that plays a variety of roles in the early development and normal adult functioning of the brain. All of these findings suggest that diseases of the brain and diseases of other organs, such as the pancreas and heart, may have more in common than previously thought.

This evidence is far from conclusive, though, and the author of the British Journal of Psychiatry study cautions, “Association does not prove causation”. Diet is determined by a plethora of economic and cultural factors, so the correlations seen in this study could merely be hiding the variables that actually determine outcome. Additional experimental evidence is needed before any real benefits can be gained from this knowledge; however, it raises many questions about possible future treatments for schizophrenia and other diseases of the brain.

Source: Peet, Malcolm. International variations in the outcome of schizophrenia and the prevalence of depression in relation to national dietary practices: an ecologicl analysis. British Journal of Psychiatry. 2004. 184, 404-408 http://bjp.rcpsych.org/