Symptoms that occur in medical outpatients often have either psychiatric or unknown causes, according to a new study.
Researchers have been looking at medical records of randomly selected patients in an Indianapolis teaching hospital. This showed that 37 per cent of symptoms reported by the 289 patients had no known cause. Another ten per cent had a psychiatric cause.

The study suggests that better diagnostic strategies are needed to assessing and treating symptoms which don't have an underlying physical cause. Where there is a psychiatric disorder, treating this may relieve the symptoms. Further analysis showed that one quarter of all symptoms persisted for at least a year after the patient's first hospital visit.

The researchers also found that men, those with multiple medical problems and those with common complaints like headaches were more likely to have a persistent symptom. Most symptoms related to pain of some kind, with coughing and trouble breathing being the most common non-pain symptoms. Black patients, those who were making their first visit to the hospital and those returning patients with improving symptoms were the most likely to have symptoms with a physical cause. So too were those who had received medicine or tests. Missed diagnoses - classifying a symptom as physical when it was not - were rare.