Reading focus
Syllabus: How Do Psychotic Experiences Develop and Persist?
Follow how the review defines experiences and the time periods over which they are counted.
Why you’re reading it. This establishes the outcome before later papers attempt to predict or explain it.
A question to consider. A person reports an unusual perception at two interviews a year apart. What can you conclude about persistence, and what would you still need to know about distress, functioning and the months between interviews?
Why this reading
How often an experience occurs and whether it recurs are different questions. This review separates new psychotic experiences from persistence and shows how definitions, observation periods and sampling shape their estimates. It provides a way to examine population patterns without treating an unusual experience as a diagnosis.
Before you read
Incidence counts new occurrences over a specified period; prevalence counts existing cases within a defined window. Here, persistence means reporting an experience at more than one time point, not necessarily having it continuously. The review concerns hallucination-like and delusion-like experiences outside a psychotic disorder. It does not cover every negative symptom, cognitive difficulty or schizotypal trait.
Read for
- Trace the eligibility rules and the handling of repeated reports from the same sample. Which populations and experiences enter each analysis?
- Compare the denominators for incidence and persistence, including the conversion to person-years. What assumptions are needed to combine different follow-up periods?
- Examine variation across studies and the limits of the age and language comparisons. A nonsignificant moderator test does not establish that settings or measures are equivalent.
Consider afterwards
- Would a repeated report at two interviews establish continuous symptoms between them? Design an observation that would distinguish recurrence from continuous persistence.
- What additional evidence would justify moving from an estimate of incidence to a claim that screening or intervention improves outcomes?
Editorial context
The search was updated in January 2023. Most included evidence came from Europe or North America, and too few comparable studies were available to pool many proposed risk factors. The authors’ prevention proposals extend beyond what incidence and persistence estimates alone establish. These estimates concern defined populations and measures, not an individual prognosis or a universal boundary between ordinary and clinical experience.