Firstly, clinical intake characteristics of a large UHR sample (n = 397) were compared across baseline year epochs (1995–2006). Characteristics showing significant differences were included in a Cox-regression to examine if they could explain the decline in transition rates. Secondly, because later cohorts show lower transition rates, ‘more stringent’ UHR-criteria were retrospectively applied to these cohorts (post-2000, n = 219), investigating if this resulted in a higher transition rate.
Results indicated that earlier cohorts presented with (1) a larger array of attenuated psychotic symptoms, (2) higher ratings on conceptual disorganization (formal thought disorder) and (3) a higher proportion of individuals with trait risk factor (all P < .001). However, these factors could not fully account for the decline in transition rates. Applying more stringent UHR-criteria to the post-2000-subsample did not substantially change the rate of transition.
Our study suggests that later UHR cohorts presented with different clinical intake characteristics than earlier cohorts. While this may have contributed to the observed decrease in transition rates to psychosis, it does not appear to fully account for this decline, suggesting other factors have also impacted on transition rates over time.