Antipsychotics and schizophrenia, and their relationship to diabetes

The relationship between diabetes and schizophrenia is complex and multifactorial. Disease- specific effects, environment and antipsychotic medications are all thought to interact and play a role. Citing a case vignette as illustration, Dr Clare Whicher, Dr Sarah Brewster and Professor Richard Holt here analyse the evidence base and provide practical management advice. John, a 28-year-old cleaner, was diagnosed with schizophrenia five years ago. His mental health had been stable for a number of years but following a stressful period at work he experienced a relapse. John was started on olanzapine in addition to aripiprazole which he had been taking since diagnosis. Three months later he presented to the emergency department with vomiting and abdominal pain. On initial assessment he was clinically dehydrated. His venous blood gas showed a significant acidosis. The admitting team initially referred John for a surgical review as they were concerned about the possibility of appendicitis. Before the surgeons arrived, a member of the team reviewed John's results and noted that he had a blood glucose of 24mmol/ L on the venous blood gas. Capillary ketones were elevated and a diagnosis of diabetic ketoacidosis was made. John was treated with a fixed-rate insulin infusion as per hospital protocol and reviewed by the diabetes team the following morning.