I am currently on my psychiatry rotation. Psychiatry is one of those peculiar specialties that tends to polarise medical students. Some dismiss it as merely asking, “And how does that make you feel?”, while others are like my housemate, whose eyes light up at the mention of psychosis and neurosis. Myself, I am approaching the specialty with an open and insatiably curious mind.

One thing I have noticed is that psychiatry throws up the sort of questions that endocrinology, say, just doesn’t.

For example, a lot of the patients I have visited tend to be religious, to a greater or lesser extent. Some have a quiet, cultural religiosity, while others have what might be described as quite odd ideas. Some of these patients have schizophrenia.

The relationship struck me. Auditory hallucinations, thought insertion, and delusions of reference are all key symptoms of schizophrenia, but none would be out of place in a sincerely devout mind. Joan of Arc’s divine command to defeat the English, Mohammed’s reception of the Koran, Moses’ arboreal arson: is this religion or schizophrenia?

Religious delusions are not uncommon in schizophrenia and mental illness. I’ve met patients who think they’re the new messiah and others who are convinced that a cabal of devils is out to get them. Interestingly, they seem to be more prevalent in Western, Christian countries, which shows the role culture can play in influencing delusions.

However, many people are religious without being mentally ill. And those with schizophrenia have the same capacity to experience a spiritual dimension in their lives. Indeed, studies have shown that people with mental illness tend to be more religious than the general population.

All well and good, but how can I differentiate between a devout religiosity and a religiously flavoured delusion? In a comprehensive review on the relationship between religion and schizophrenia, Mohr and Huguelet offer a litmus test. A delusion will appear as a delusion, and in the context of other symptoms of mental illness. So far, so obvious. Lastly, they state that person’s lifestyle, behaviour and goals are more in keeping with mental disorder than a personally enriching life experience. Basically, if it looks like a duck, and sounds like a duck, it’s probably a mentally ill duck.

Returning to the patients and their odd ideas, perhaps now I can resolve my question. Are they psychotic? Some, maybe, but others showed no other signs of delusion. Instead, their faith, in the face of the challenges of their illness, seems to be something positive for them. Spiritual experience in schizophrenia is not always the product of distorted thinking.

These patients set me off on a fascinating line of inquiry, yet I wouldn’t have even considered it if the odd ideas of patients had come up during a diabetic foot clinic.

Rhys Davies is a fifth year medical student at Imperial College, London.