The prevalence and pathological value of attenuated psychotic symptoms (APS) and other at-risk criteria in general population the age range of highest risk of (beginning) psychosis, when assessed in the same way as in help-seeking persons, is still unclear.

In 2 complimentary studies, we studied the 3-month prevalence of ultra-high risk and basic symptom at-risk criteria assessed with the Structured Interview for Psychosis-Risk Syndromes (SIPS) and the Schizophrenia Proneness Instrument, Adult version (SPI-A) in random Swiss general population samples of 8–17 years and 16–40 years. Children and adolescents were assessed in a face-to-face, young adults in a telephone interview by trained clinical psychologists. Exclusion criteria were communication problems andl ife-time psychosis.

1’229 interviews with young adults and 55 interviews with children and adolescents were completed. While 2.8% of the young adults acknowledged the presence of any one at-risk criterion within the last 3 months, 9.1% of the children and adolescents did so. An age-related difference was also found in the prevalence of at least 1 lifetime at-risk phenomenon: 25.2% in young adults and 45.5% in children and adolescents.

While at-risk phenomena occur in a quarter of young adults of the general population and even in nearly half of the children and adolescents at least temporarily, only a minority reports sufficient recency, frequency or change in severity of these phenomena to meet present at-risk criteria according to SIPS and SPI-A. This highlights the importance of the recency, frequency or behavior-/conviction-related change-in-severity criteria included in the at-risk criteria.