Abstract
Valid measurement of group differences in self-reported psychotic-like experiences (PLEs) requires knowing any group-specific measurement properties of the instruments. We investigated the measurement invariance of the 21-item Prodromal Questionnaire–Brief (PQ-B) questionnaire across gender, ethnic minority/majority status, and presence of depressive symptoms in two different US non-clinical undergraduate samples (N = 1,099). For each item, endorsement of the experience and the associated distress were combined for analysis. A unidimensional model of the PQ-B fit the data well. Across genders, the PQ-B showed configural and metric, but not full scalar invariance; there were statistically significant differences in eight thresholds of six items, most being higher endorsement thresholds for self-identified females. Partial scalar invariance was also found for ethnic status, with five thresholds of three items being higher for the minority participants. For depressive symptomatology, defined as the top quintile by the Beck Depression Inventory–II, partial scalar invariance required dropping one item, after which there were statistically significant differences only in two response thresholds. Overall, a wide range of PLE questionnaire items were found to be robust to gender and ethnicity effects, strengthening confidence in found group differences in PLEs. Although full scalar invariance could not be ascertained for any of the group comparisons, the few found scalar differences across groups were small, with minimal impact on group PLE estimates. However, since PLEs are easily conceptually entangled with depression symptoms, similar items should be considered for exclusion if separable constructs are the target of investigation.
Highlights
Psychotic-like experiences (PLEs) are abnormal perceptions or thoughts that resemble the positive symptoms of psychotic disorders
A richer understanding of psychotic-like experiences (PLEs) can facilitate a more complete picture of the entire psychosis spectrum. Regardless of their relation with future psychosis, elucidating factors related to PLEs remains important as they have been associated with help-seeking behavior [3], impaired functioning [4,5,6], psychopathology and psychiatric diagnoses [7,8,9], as well as later hospitalization and suicidality [10,11,12,13]
Though semi-structured interviews are the gold standard for detecting clinically relevant PLEs thought to indicate psychosis risk, several questionnaires have been developed for first-stage clinical screening, which are in content very similar to questionnaires for measuring PLEs in the general population
Summary
Psychotic-like experiences (PLEs) are abnormal perceptions or thoughts that resemble the positive symptoms of psychotic disorders. A richer understanding of PLEs can facilitate a more complete picture of the entire psychosis spectrum. Regardless of their relation with future psychosis, elucidating factors related to PLEs remains important as they have been associated with help-seeking behavior [3], impaired functioning [4,5,6], psychopathology and psychiatric diagnoses [7,8,9], as well as later hospitalization and suicidality [10,11,12,13]. Careful examination of the measurement biases in such instruments is warranted
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