Over the past eight months, I have been spending most of my time working on an undergraduate thesis project in the field of psychiatry. One of the many questionnaires I am using to assess presence of psychopathology in the sample for my research project is the PLE, or scale of Psychotic-Like Experiences. Scoring this scale got me thinking about how useful self-reports are in diagnosing psychosis or mania due to cognitive distortion and lack of insight.

Take for example, a subject suffering from a paranoid delusion in which they believe that the government is tracking their every move. In a question on a self-report measure that assesses delusions, they might lie about the presence of that symptom out of fear that the government is tracking their responses. Is it counterproductive to try to get someone who is unaware of their ailment to rate it?

One way to get around unintentional concealment of psychotic symptoms in self-report measures is to supplement them with clinician-rated measures. In an example of a best case scenario, one study found that scores on a self-report measure called the Revised Behavior and Symptom Identification Scale (BASIS-R) were highly correlated with scores on the clinician-rated UCLA Brief Psychiatric Rating Scale (BPRS).

A comprehensive research paper on the Insight Scale, a self-report scale of psychotic symptoms, found that not only are test-retest correlations high, but also that internal reliability was relatively high among patients with more severe symptoms. The Insight Scales’ construct, criterion, and concurrent validities also proved to be quite high.

Another study, however, found only moderate concordance between self-reported and other-rated measures of schizophrenia. Interestingly, patients who reported themselves as having lower symptoms than third-party raters tended to haveless years of education, more negative symptoms, and overall lesser functioning. Therefore, self-report measures can be trusted, but only to a certain extent and in certain groups.

I would remain skeptical of self-report measures for psychosis. Although it is no doubt more time and cost efficient to administer self-reports, we must be sensitive to the unique challenges faced by individuals with psychotic symptoms. As much as they can, clinical psychologists should endeavour to use multiple reliable methods to reach a diagnosis — and this should hold true for all psychiatric disorders.