Surprising Number of People Show Signs of Psychosis

A number of people may experience psychotic symptoms even if they do not have a full-blown psychotic disorder, various studies have suggested. For example, the first National Comorbidity Survey, published in 1996, found that 28 percent of Americans had experienced psychotic symptoms at some point in their lives. European studies placed the percentage between 6 percent and 18 percent.

However, none of these studies evaluated how many people experience such symptoms over the long term. So Wulf Roessler, M.D., a professor of clinical and social psychiatry at the University of Zurich in Switzerland, and his colleagues decided to do so.

Results from their 20-year investigation appeared in the May Schizophrenia Research.

Roessler and his group started with 4,600 19- or 20-year-olds representative of their age group in the Zurich area. Each was mailed and asked to fill out the Symptom Checklist 90-R (SCL90-R). The SCL90-R is a comprehensive self-report questionnaire containing 90 questions, covering a broad range of psychiatric symptoms. From the individuals who responded, the researchers selected 591 to participate in their 20-year longitudinal study. Two-thirds of them had scored high in psychiatric symptoms on the SCL90-R, and the remaining one-third had scored within the normal range. The reason why they conducted their inquiry in this fashion, Roessler explained to Psychiatric News, was “because it is a time- and money-saving way to conduct longitudinal studies and because one wants to increase the chances of assessing rare symptoms.”

When the subjects were aged 21, 23, 28, 30, 35, and 41, they were asked not only to fill out the SCL90-R, but to undergo a semistructured interview. This way the scientists could not just plot their experiences with various psychotic symptoms, but also diagnose them, according to DSM criteria, for schizophrenia. Out of the initial 591 subjects, 372 completed the entire study.

Roessler and his team found that a large proportion—58 percent—reported having experienced psychotic symptoms at one time or another. For example, at age 21, 38 percent reported that someone else could control their thoughts, and 19 percent reported that other people were aware of their private thoughts. At age 30, 30 percent reported that they felt lonely even when with other people. At age 41, about 33 percent said they were being watched by other people.

As time went by, the subjects experiencing psychotic symptoms could generally be placed in two groups—those with the nuclear symptoms of schizophrenia such as auditory hallucinations and thought-broadcasting, and those with schizotypal symptoms such as odd beliefs, suspiciousness, and a reduced capacity for close relationships. Nonetheless, 6 out of 10 subjects who had experienced a consistently high level of schizotypal symptoms also experienced a continuously high level of schizophrenia nuclear ones, and those who remained highly symptomatic in either domain experienced a lot of difficulties in their lives on factors such as partnerships, careers, or contact with the justice system.