THE ONLY good that stems from the reports of murder and violence that owe their origins to mental disease — and too often the over-optimism that has allowed a patient to be the discharged too soon — is that generally Marjorie Wallace, of Sane, will be asked to comment. She invariably gives a commonsense opinion, coupled with a plea for more research and a better-funded care service. The latest example was of the man who was discharged from hospital to welfare accommodation, where he was involved in the gruesome death of a fellow resident.

For years there has been a suggestion that wheat and gluten sensitivity may be a factor in the development of schizophrenia. Studies have indicated that a wheat-free diet improves its symptoms. The idea that diet may cause psychiatric or psychological problems invariably produces howls of mirth from the more cynical and detached members of the medical profession, but the association between gluten and schizophrenia has been rumoured for so long that it cannot be ignored.

Recently the BMJ has provided more evidence for the link in a study of the relationship between coeliac disease and schizophrenia. Coeliac disease — also known as gluten enteropathy — is an unusual sensitivity to gluten (a mixture of two proteins present in wheat and rye). Sensitivity gives rise to gastro-intestinal symptoms, deficiencies in absorption of nutrients and general wasting with associated ill health.

Researchers from the Department of Public Health at Johns Hopkins University and Aarhus University in Denmark studied 8,000 people who were admitted to a Danish psychiatric unit over 20 years with a diagnosis of schizophrenia. The data showed that coeliac disease, in this group of patients, was a risk factor for schizophrenia. Although the association is significant, it is likely that only a small proportion of cases of schizophrenia will have coeliac disease, and likewise only a small minority of coeliac patients will develop schizophrenia.

Other factors that are known to trigger schizophrenia in those with a genetic liability to it are viral infections — which may be related to the month of birth, raising the possibility that the child could have been influenced in utero — the exposure to drugs such as cannabis and cocaine, and to stress.

Stress, so far as schizophrenia is concerned, includes both that linked to poverty and deprivation and that stemming from competition — the competition of examinations, or merely the struggle to achieve the expectations of family and friends.

Schizophrenia is one of the most feared of diseases, and is said to affect one in 100. Many more people from the same genetic background carry the genes for schizophrenia, in whom psychological problems, if present, are not so severe. Since they have no obvious psychotic illness they are not labelled as having schizophrenia, but could be vulnerable to trigger factors. It is these patients who are particularly important.

Protect them from trigger factors, including cannabis, stress and, who now knows, gluten, and their life might be splendidly productive, even if slightly eccentric. Give them an adverse environment and, conversely, it might be a life of trouble.