Declining transition rate in ultra high risk (prodromal) services: dilution or reduction of risk?

Abstract

There is growing interest in the prodromal stage of psychotic disorders, with many services now providing care for these "ultra high risk" (UHR) individuals. However, a reduction in the rate of transition to psychosis has been suspected over the last few years. This has implications for the use of interventions in this population and for the validity of research findings. This study examined the transition rate in one UHR service, the Personal Assessment and Crisis Evaluation Clinic, over the years 1995-2000 and investigated possible causes for the transition rate reduction. There was evidence for a declining transition rate, with each successive year showing a rate 0.80 times that of the preceding year. Functioning and symptom level were not responsible for the change. The decreased transition rate was partly explained by a reduction in the duration of symptoms of patients prior to receiving help. That is, UHR individuals are being detected and provided with care earlier than in the past. Thus, the decline in transition rate may be due to treatment being more effective at this very early stage of illness or it may be due to finding more false positives who were never at risk of psychosis, ie, a "dilution" effect. Given that it is not possible to distinguish between these alternatives at least phenotypically at present, perhaps it is time to rethink the role and practice of UHR clinics. Patients presenting to them need help. It may be that we need to aim to prevent a range of target syndromes.

Fig. 1.

Theoretical Distinction Between False Positives and False False Positives. (A) True positive: psychosis threshold is crossed. (B) False positive: psychosis threshold is not crossed. (C) False false positive: psychosis threshold is not crossed but would have been in the absence of intervention or some change in circumstance.

Fig. 2.

Mean Duration of Symptoms [days (standard deviation)] Prior to Receiving Psychiatric Help in Successive Personal Assessment and Crisis Evaluation ultra high risk Cohorts 1995–2000.

Fig. 3.

Theoretical Model of Different Samples. PLEs = psychotic-like experiences. Level 0 individuals are most common, level 5 least common. Subjects in early Personal Assessment and Crisis Evaluation cohorts were recruited mainly from level 3. Later cohorts probably included individuals from both level 3 and level 2. It is possible that some young people from level 1 were also included (reproduced with permission of Schizophrenia Research22).