At risk mental state, also referred to as clinical high risk(CHR) or ultra high risk (UHR), [1] is the clinical presentation of those considered at risk of developing psychosis or schizophrenia. [2] Such states were formerly considered as prodromal phases, during which individuals experience non-specific or attenuated symptoms of psychosis until the onset of an initial psychotic episode [3] , but this view is no longer prevalent as a prodromal period cannot be confirmed unless the emergence of the condition has occurred. [4] The original specialist service for those with subclinical symptoms of psychosis was The Pace Clinic [5] in Melbourne, Australia. [6] Other clinics have since developed around the world. [7] [8] [9] [10]
Individuals who meet criteria for CHR often experience both positive symptoms (i.e., symptoms that reflect a loss of contact with reality, including delusions, hallucinations, and disorganized thoughts/behavior) and negative symptoms (i.e., symptoms that represent a deficit in experiences, such as blunted affect, anhedonia, avolition, and asociality) that do not meet the threshold for a chronic psychotic disorder. [11] The CHR state has been demonstrated to be specific for the development of psychosis, as individuals who meet criteria are not at enhanced risk for developing other mental health disorders, such as bipolar or other mood disorders and anxiety disorders. [12] Despite this specificity of CHR criteria, the CHR population is quite heterogeneous. [13]
A variety of different instruments have been developed to identify individuals meeting CHR criteria, with the most popular being the Structured Interview for Psychosis-Risk Syndromes (SIPS) [14] and the Comprehensive Assessment of At-Risk Mental States (CAARMS) [15] , which were harmonized into a single instrument in 2024, the Positive SYmptoms and Diagnostic Criteria for the CAARMS Harmonized with the SIPS (PSYCHS). [16] Symptoms are described with respect to their severity, frequency, and attribution (i.e., symptoms cannot be attributed to another disorder). However, in spite of the harmonization efforts, the persisting differences in the CHR criteria between these instruments, such as the length of time during which symptoms are present (e.g., SIPS requires symptoms to be present within the last month [14] , whereas CAARMS considers symptoms over the past year [16] ), reflect the heterogeneous nature of the population and the challenges of identifying the salient features of the high risk state.
Within the framework of the SIPS, there are three distinct risk syndromes, each of which is characterized by the presence of brief and/or intermittent fully psychotic symptoms (BIPS), attenuated positive symptoms (APSS), or genetic risk and deterioration (GRDS). [14] Although individuals who meet criteria for APSS are the most prevalent in CHR populations [1] , research suggests that the risk of conversion to chronic psychosis differs for each of these syndrome subgroups, with BIPS presenting a greater conversion risk and distinct prognosis when compared to APSS and GRDS, [17] which has led some to argue that BIPS should be removed from CHR and that its prognosis does not differ significantly from that of brief psychotic disorder. [18] [19] The enhanced conversion risk in BIPS aligns with findings that have identified the severity of symptoms as being one of the most influential predictors of conversion. [20] [21] [22]
There has been some considerable development of how the concept can be applied clinically. [23] [24] [25] [26] In the revision of the DSM-5, attenuated psychosis syndrome was included as a diagnosis as an Other Specified Schizophrenia Spectrum and Other Psychotic Disorder. [27]