“We wanted to understand what’s common and what’s protecting people who hallucinate but who don’t require psychological intervention,” he says. Even in the absence of these predisposing factors, approximately one in 20 people hear voices or see visual hallucinations at least once in their lifetimes, according to mental health surveys conducted by the World Health Organization. Whereas most researchers have focused on the brain abnormalities that occur in people suffering at an extreme end of this spectrum, Powers and his colleagues have turned their attention to milder cases in a new study. Drugs, sleep deprivation and migraines can often trigger the illusion of sounds or sights that are not there. Healthy people also experience hallucinations. But increasing evidence over the past two decades suggests hearing imaginary sounds is not always a sign of mental illness. Some patients report hearing voices others hear phantom melodies.
Auditory hallucinations are the most common type experienced. The condition is often a hallmark of psychosis, occurring in an estimated 60 to 70 percent of people with schizophrenia, and in a subset of those diagnosed with bipolar disorder, dementia and major depression.
At his psychiatric clinic in the Connecticut Mental Health Center, Albert Powers sees people every day who experience hallucinations.