Psychosis is common in Alzheimer’s disease and affects between about 40 percent and 50 percent of people over the course of the disease. It causes significant distress to the patient and to families and caregivers. Psychosis itself does not describe a disease so much as an abnormal condition of the mind where people find it difficult to tell what is real and what - in its simplest terms - is imagination.

In a neurodegenerative disease such as Alzheimer’s disease (AD) where confusion is...