Ultra-high risk (UHR) criteria are defined by attenuated and/or transient full-blown psychotic symptoms and/or a combination of genetic risk factor and deterioration of functioning. To achieve a higher predictive specificity and a clear threshold of clinical importance, functional impairment has been considered as an obligate part of all UHR criteria.

In the European Prediction of Psychosis Study (EPOS)N = 37 participants converted to psychosis, n = 146 completed the whole 18-month follow-up period without conversion. Assessed by the Global Assessment of Functioning Scale, modified version (GAF-M), the following functional states were considered: Considered GAF-M: ≤30%/≤10% reduction of baseline scores related to highest scores in the previous year; scores ≤70/≤60.

The GAF reduction criteria led to a very unfavorable loss of sensitivity, even, if only 10% were demanded. This was accompanied by correspondingly unfavorable accuracy measures. Introducing functional impairment criteria defined by the current state reported to be predictive for psychiatric caseness (score ≤ 70) or to define serious impairment (score ≤ 60) (Kessler et al., 2002, 2003) kept sensitivity at a perfectly high level, yet did not produce any gain of specificity.

These results were certainly be caused by the fact that the whole group showed already low GAF-M scores in the previous year. Thus, a functional impairment criterion proved not to be useful to improve prediction. However, a combination of APS or BLIPS with a ‘clinical status’ criterion of GAF-M ≤ 70 may be considerable to demonstrate a strong need for intervention.