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Negative psychotic symptoms and impaired role functioning predict transition outcomes in the at-risk mental state: a latent class cluster analysis study

Published online by Cambridge University Press:  27 February 2013

L. R. Valmaggia ,
D. Stahl ,
A. R. Yung ,
B. Nelson ,
P. Fusar-Poli ,
P. D. McGorry  and
P. K. McGuire
L. R. Valmaggia*
Affiliation:
King's College London, Institute of Psychiatry, London, UK Outreach and Support in South London Service (OASIS), South London and Maudsley NHS Trust, London, UK
D. Stahl
Affiliation:
King's College London, Institute of Psychiatry, London, UK
A. R. Yung
Affiliation:
Orygen Youth Health, Department of Psychiatry, University of Melbourne, Australia Institute of Brain, Behaviour & Mental Health, University of Manchester, UK
B. Nelson
Affiliation:
Orygen Youth Health, Department of Psychiatry, University of Melbourne, Australia
P. Fusar-Poli
Affiliation:
King's College London, Institute of Psychiatry, London, UK Outreach and Support in South London Service (OASIS), South London and Maudsley NHS Trust, London, UK
P. D. McGorry
Affiliation:
Orygen Youth Health, Department of Psychiatry, University of Melbourne, Australia
P. K. McGuire
Affiliation:
King's College London, Institute of Psychiatry, London, UK Outreach and Support in South London Service (OASIS), South London and Maudsley NHS Trust, London, UK
*
*Address for correspondence: Dr L. R. Valmaggia, King's College London, King's Health Partners, Institute of Psychiatry (PO77), De Crespigny Park, London SE5 8AF, UK. (Email: lucia.valmaggia@kcl.ac.uk)
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Abstract

Background

Many research groups have attempted to predict which individuals with an at-risk mental state (ARMS) for psychosis will later develop a psychotic disorder. However, it is difficult to predict the course and outcome based on individual symptoms scores.

Method

Data from 318 ARMS individuals from two specialized services for ARMS subjects were analysed using latent class cluster analysis (LCCA). The score on the Comprehensive Assessment of At-Risk Mental States (CAARMS) was used to explore the number, size and symptom profiles of latent classes.

Results

LCCA produced four high-risk classes, censored after 2 years of follow-up: class 1 (mild) had the lowest transition risk (4.9%). Subjects in this group had the lowest scores on all the CAARMS items, they were younger, more likely to be students and had the highest Global Assessment of Functioning (GAF) score. Subjects in class 2 (moderate) had a transition risk of 10.9%, scored moderately on all CAARMS items and were more likely to be in employment. Those in class 3 (moderate–severe) had a transition risk of 11.4% and scored moderately severe on the CAARMS. Subjects in class 4 (severe) had the highest transition risk (41.2%), they scored highest on the CAARMS, had the lowest GAF score and were more likely to be unemployed. Overall, class 4 was best distinguished from the other classes on the alogia, avolition/apathy, anhedonia, social isolation and impaired role functioning.

Conclusions

The different classes of symptoms were associated with significant differences in the risk of transition at 2 years of follow-up. Symptomatic clustering predicts prognosis better than individual symptoms.

Keywords

At-risk mental stateearly detectionearly interventionnegative symptomspsychosis
Type
Original Articles
Information
Psychological Medicine , Volume 43 , Issue 11 , November 2013 , pp. 2311 - 2325
Copyright
Copyright © Cambridge University Press 2013 

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References

Amminger, GP, Leicester, S, Yung, AR, Phillips, LJ, Berger, GE, Francey, SM, Yuen, HP, McGorry, PD (2006). Early-onset of symptoms predicts conversion to non-affective psychosis in ultra-high risk individuals. Schizophrenia Research 84, 67–76.CrossRefGoogle ScholarPubMed
Andreasen, NC, Carpenter, WT Jr. (1993). Diagnosis and classification of schizophrenia. Schizophrenia Bulletin 19, 199–214.CrossRefGoogle ScholarPubMed
APA (1994). Diagnostic and Statistical Manual of Mental Disorders, 4th edn.American Psychiatric Association: Washington, DC.Google Scholar
Bentall, RP, Jackson, HF, Pilgrim, D (1988). Abandoning the concept of ‘schizophrenia’: some implications of validity arguments for psychological research into psychotic phenomena. British Journal of Clinical Psychology 27, 303–324.CrossRefGoogle ScholarPubMed
Buchanan, RW, Carpenter, WT Jr. (1997). The neuroanatomies of schizophrenia. Schizophrenia Bulletin 23, 367–372.CrossRefGoogle ScholarPubMed
Cannon, TD, Cadenhead, K, Cornblatt, B, Woods, SW, Addington, J, Walker, E, Seidman, LJ, Perkins, D, Tsuang, M, McGlashan, T, Heinssen, R (2008). Prediction of psychosis in youth at high clinical risk: a multisite longitudinal study in North America. Archives of General Psychiatry 65, 28–37.CrossRefGoogle ScholarPubMed
Castle, DJ, Sham, PC, Wessely, S, Murray, RM (1994). The subtyping of schizophrenia in men and women: a latent class analysis. Psychological Medicine 24, 41–51.CrossRefGoogle ScholarPubMed
Cornblatt, BA, Auther, AM, Niendam, T, Smith, CW, Zinberg, J, Bearden, CE, Cannon, TD (2007). Preliminary findings for two new measures of social and role functioning in the prodromal phase of schizophrenia. Schizophrenia Bulletin 33, 688–702.CrossRefGoogle ScholarPubMed
Cornblatt, BA, Lencz, T, Smith, CW, Correll, CU, Auther, AM, Nakayama, E (2003). The schizophrenia prodrome revisited: a neurodevelopmental perspective. Schizophrenia Bulletin 29, 633–651.CrossRefGoogle ScholarPubMed
Davidsen, KA (2009). Anomalous self-experience in adolescents at risk of psychosis. Clinical and conceptual elucidation. Psychopathology 42, 361–369.Google ScholarPubMed
Demjaha, A, Valmaggia, L, Stahl, D, Byrne, M, McGuire, P (2012). Disorganization/cognitive and negative symptom dimensions in the at-risk mental state predict subsequent transition to psychosis. Schizophrenia Bulletin 38, 351–359.CrossRefGoogle ScholarPubMed
French, P, Morrison, AP (2004). Early Detection and Cognitive Therapy for People at High Risk of Developing Psychosis: A Treatment Approach. Wiley-Blackwell: Chichester.CrossRefGoogle Scholar
Fusar-Poli, P, Bonoldi, I, Yung, AR, Borgwardt, S, Kempton, MJ, Valmaggia, L, Barale, F, Caverzasi, E, McGuire, P (2012 a). Predicting psychosis meta-analysis of transition outcomes in individuals at high clinical risk. Archives of General Psychiatry 69, 220–229.CrossRefGoogle ScholarPubMed
Fusar-Poli, P, Borgwardt, S, Bechdolf, A, Addington, J, Riecher-Rossler, A, Schultze-Lutter, F, Keshavan, M, Wood, S, Ruhrmann, S, Seidman, LJ, Valmaggia, L, Cannon, T, Velthorst, E, de Haan, L, Cornblatt, B, Bonoldi, I, Birchwood, M, McGlashan, T, Carpenter, W, McGorry, P, Klosterkotter, J, McGuire, P, Yung, A (2012 b). The psychosis high-risk state: a comprehensive state-of-the-art review. Archieves of General Psychiatry. Published online: 19 November 2012. doi:10.1001/jamapsychiatry.2013.269.Google Scholar
Fusar-Poli, P, Byrne, M, Badger, S, Valmaggia, LR, McGuire, PK (2012 c). Outreach and support in South London (OASIS), 2001–2011: ten years of early diagnosis and treatment for young individuals at high clinical risk for psychosis. European Psychiatry. Published online: 5 November 2012. doi:10.1016/j.eurpsy.2012.08.002.Google ScholarPubMed
Fusar-Poli, P, Byrne, M, Valmaggia, L, Day, F, Tabraham, P, Johns, L, McGuire, P (2010). Social dysfunction predicts two years clinical outcome in people at ultra high risk for psychosis. Journal of Psychiatric Research 44, 294–301.CrossRefGoogle ScholarPubMed
Fusar-Poli, P, Deste, G, Smieskova, R, Barlati, S, Yung, AR, Howes, O, Stieglitz, RD, Vita, A, McGuire, P, Borgwardt, S (2012 d). Cognitive functioning in prodromal psychosis: a meta-analysis. Archives of General Psychiatry 69, 562–571.CrossRefGoogle ScholarPubMed
Fusar-Poli, P, Meneghelli, A, Valmaggia, L, Allen, P, Galvan, F, McGuire, P, Cocchi, A (2009). Duration of untreated prodromal symptoms and 12-month functional outcome of individuals at risk of psychosis. British Journal of Psychiatry 194, 181–182.CrossRefGoogle ScholarPubMed
Fusar-Poli, P, Nelson, B, Valmaggia, L, Yung, AR, McGuire, PK (2012 e). Comorbid depressive and anxiety disorders in 509 individuals with an at-risk mental state: impact on psychopathology and transition to psychosis. Schizophrenia Bulletin. Published online: 22 November 2012. doi:10.1093/schbul/sbs13.Google ScholarPubMed
Fusar-Poli, P, Valmaggia, L, McGuire, P (2007). Can antidepressants prevent psychosis? Lancet 370, 1746–1748.CrossRefGoogle ScholarPubMed
Garety, PA, Kuipers, E, Fowler, D, Freeman, D, Bebbington, PE (2001). A cognitive model of the positive symptoms of psychosis. Psychological Medicine 31, 189–195.CrossRefGoogle ScholarPubMed
Herbener, ES, Harrow, M (2004). Are negative symptoms associated with functioning deficits in both schizophrenia and nonschizophrenia patients? A 10-year longitudinal analysis. Schizophrenia Bulletin 30, 813–825.CrossRefGoogle ScholarPubMed
Klosterkotter, J, Schultze-Lutter, F, Bechdolf, A, Ruhrmann, S (2011). Prediction and prevention of schizophrenia: what has been achieved and where to go next? World Psychiatry 10, 165–174.CrossRefGoogle ScholarPubMed
Larsen, TK, Friis, S, Haahr, U, Johannessen, JO, Melle, I, Opjordsmoen, S, Rund, BR, Simonsen, E, Vaglum, PV, McGlashan, TH (2004). Premorbid adjustment in first-episode non-affective psychosis: distinct patterns of pre-onset course. British Journal of Psychiatry 185, 108–115.CrossRefGoogle ScholarPubMed
Lataster, T, Valmaggia, L, Lardinois, M, van Os, J, Myin-Germeys, I (2012). Increased stress reactivity: a mechanism specifically associated with the positive symptoms of psychotic disorder. Psychological Medicine. Published online: 31 October . doi:10.1017/S0033291712002279.Google ScholarPubMed
Lazarsfeld, PF, Henry, NW (1968). Latent Structure Analysis. Wiley: New York.Google Scholar
Lencz, T, Smith, CW, Auther, A, Correll, CU, Cornblatt, B (2004). Nonspecific and attenuated negative symptoms in patients at clinical high-risk for schizophrenia. Schizophrenia Research 68, 37–48.CrossRefGoogle ScholarPubMed
Lin, TH, Dayton, CM (1997). Model selection information criteria for non-nested latent class models. Journal of Educational and Behavioral Statistics 22, 249–264.CrossRefGoogle Scholar
Maric, N, Krabbendam, L, Vollebergh, W, de Graaf, R, van Os, J (2003). Sex differences in symptoms of psychosis in a non-selected, general population sample. Schizophrenia Research 63, 89–95.CrossRefGoogle Scholar
Masillo, A, Day, F, Laing, J, Howes, O, Fusar-Poli, P, Byrne, M, Bhattacharyya, S, Fiori Nastro, P, Girardi, P, McGuire, PK, Valmaggia, LR (2012). Interpersonal sensitivity in the at-risk mental state for psychosis. Psychological Medicine 42, 1835–1845.CrossRefGoogle ScholarPubMed
McGlashan, TH, Addington, J, Cannon, T, Heinimaa, M, McGorry, P, O'Brien, M, Penn, D, Perkins, D, Salokangas, RK, Walsh, B, Woods, SW, Yung, A (2007). Recruitment and treatment practices for help-seeking ‘prodromal’ patients. Schizophrenia Bulletin 33, 715–726.CrossRefGoogle ScholarPubMed
McGlashan, TH, Fenton, WS (1992). The positive-negative distinction in schizophrenia. Review of natural history validators. Archives of Geneneral Psychiatry 49, 63–72.CrossRefGoogle ScholarPubMed
McGlashan, TH, Johannessen, JO (1996). Early detection and intervention with schizophrenia: rationale. Schizophrenia Bulletin 22, 201–222.CrossRefGoogle ScholarPubMed
McLachlan, GJ, Peel, D (2000). Finite Mixture Models. Wiley: New York.CrossRefGoogle Scholar
Meng, H, Schimmelmann, BG, Koch, E, Bailey, B, Parzer, P, Gunter, M, Mohler, B, Kunz, N, Schulte-Markwort, M, Felder, W, Zollinger, R, Burgin, D, Resch, F (2009). Basic symptoms in the general population and in psychotic and non-psychotic psychiatric adolescents. Schizophrenia Research 111, 32–38.CrossRefGoogle ScholarPubMed
Miller, TJ, Zipursky, RB, Perkins, D, Addington, J, Woods, SW, Hawkins, KA, Hoffman, R, Preda, A, Epstein, I, Addington, D, Lindborg, S, Marquez, E, Tohen, M, Breier, A, McGlashan, TH (2003). The PRIME North America randomized double-blind clinical trial of olanzapine versus placebo in patients at risk of being prodromally symptomatic for psychosis. II. Baseline characteristics of the ‘prodromal’ sample. Schizophrenia Research 61, 19–30.CrossRefGoogle ScholarPubMed
Morrison, AP, French, P, Parker, S, Roberts, M, Stevens, H, Bentall, RP, Lewis, SW (2007). Three-year follow-up of a randomized controlled trial of cognitive therapy for the prevention of psychosis in people at ultrahigh risk. Schizophrenia Bulletin 33, 682–687.CrossRefGoogle ScholarPubMed
Muthén, BO, Muthén, LK (2000). The development of heavy drinking and alcohol-related problems from ages 18 to 37 in a U.S. national sample. Journal of Studies on Alcohol 61, 290–300.CrossRefGoogle Scholar
Muthén, LK, Muthén, BO (2006). Mplus: Statistical Analysis with Latent Variables (Version 4.1). Muthen & Muthen: Los Angeles, CA.Google Scholar
Myin-Germeys, I, van Os, J (2007). Stress-reactivity in psychosis: evidence for an affective pathway to psychosis. Clinical Psychology Review 27, 409–424.CrossRefGoogle ScholarPubMed
Nelson, B, Fornito, A, Harrison, BJ, Yücel, M, Sass, LA, Yung, AR, Thompson, A, Wood, SJ, Pantelis, C, McGorry, PD (2009 a). A disturbed sense of self in the psychosis prodrome: linking phenomenology and neurobiology. Neuroscience and Biobehavioral Reviews 33, 807–817.CrossRefGoogle ScholarPubMed
Nelson, B, Sass, LA, Skodlar, B (2009 b). The phenomenological model of psychotic vulnerability and its possible implications for psychological interventions in the ultra-high risk (‘prodromal’) population. Psychopathology 42, 283–292.CrossRefGoogle ScholarPubMed
Parnas, J (2011). A disappearing heritage: the clinical core of schizophrenia. Schizophrenia Bulletin 37, 1121–1130.CrossRefGoogle ScholarPubMed
Parnas, J, Handest, P (2003). Phenomenology of anomalous self-experience in early schizophrenia. Comprehensive Psychiatry 44, 121–134.CrossRefGoogle ScholarPubMed
Phillips, LJ, McGorry, PD, Yuen, HP, Ward, J, Donovan, K, Kelly, D, Francey, SM, Yung, AR (2007). Medium term follow-up of a randomized controlled trial of interventions for young people at ultra high risk of psychosis. Schizophrenia Research 96, 25–33.CrossRefGoogle ScholarPubMed
Phillips, LJ, Yung, AR, McGorry, PD (2000). Identification of young people at risk of psychosis: validation of Personal Assessment and Crisis Evaluation Clinic intake criteria. Australian and New Zealand Journal of Psychiatry 34, S164–S169.CrossRefGoogle ScholarPubMed
Phillips, LJ, Yung, AR, Yuen, HP, Pantelis, C, McGorry, PD (2002). Prediction and prevention of transition to psychosis in young people at incipient risk for schizophrenia. American Journal of Medical Genetics 114, 929–937.CrossRefGoogle ScholarPubMed
Raballo, A, Laroi, F (2011). Psychosis risk syndrome and DSM-5: time for a dimensional approach to at-risk mental states? Clinical Schizophrenia and Related Psychoses 5, 155–158.CrossRefGoogle ScholarPubMed
Raine, A (1992). Sex differences in schizotypal personality in a non-clinical population. Journal of Abnormal Psychology 101, 361–364.CrossRefGoogle Scholar
Riecher-Rossler, A, Gschwandtner, U, Aston, J, Borgwardt, S, Drewe, M, Fuhr, P, Pfluger, M, Radu, W, Schindler, C, Stieglitz, RD (2007). The Basel early-detection-of-psychosis (FEPSY)-study – design and preliminary results. Acta Psychiatrica Scandinavica 115, 114–125.CrossRefGoogle ScholarPubMed
Riecher-Rossler, A, Pflueger, MO, Aston, J, Borgwardt, SJ, Brewer, WJ, Gschwandtner, U, Stieglitz, RD (2009). Efficacy of using cognitive status in predicting psychosis: a 7-year follow-up. Biological Psychiatry 66, 1023–1030.CrossRefGoogle Scholar
Roy, MA, Maziade, M, Labbe, A, Merette, C (2001). Male gender is associated with deficit schizophrenia: a meta-analysis. Schizophrenia Research 47, 141–147.CrossRefGoogle ScholarPubMed
Ruhrmann, S, Schultze-Lutter, F, Salokangas, RK, Heinimaa, M, Linszen, D, Dingemans, P, Birchwood, M, Patterson, P, Juckel, G, Heinz, A, Morrison, A, Lewis, S, von Reventlow, HG, Klosterkotter, J (2010). Prediction of psychosis in adolescents and young adults at high risk: results from the prospective European prediction of psychosis study. Archives of General Psychiatry 67, 241–251.CrossRefGoogle Scholar
Schultz, SK, Miller, DD, Oliver, SE, Arndt, S, Flaum, M, Andreasen, NC (1997). The life course of schizophrenia: age and symptom dimensions. Schizophrenia Research 23, 15–23.CrossRefGoogle ScholarPubMed
Seidman, LJ, Giuliano, AJ, Meyer, EC, Addington, J, Cadenhead, KS, Cannon, TD, McGlashan, TH, Perkins, DO, Tsuang, MT, Walker, EF, Woods, SW, Bearden, CE, Christensen, BK, Hawkins, K, Heaton, R, Keefe, RSE, Heinssen, R, Cornblatt, BA; North American Prodrome Longitudinal Study (NAPLS) Group (2010). Neuropsychology of the prodrome to psychosis in the NAPLS consortium: relationship to family history and conversion to psychosis. Archives of General Psychiatry 67, 578–588.CrossRefGoogle ScholarPubMed
Sham, PC, Castle, DJ, Wessely, S, Farmer, AE, Murray, RM (1996). Further exploration of a latent class typology of schizophrenia. Schizophrenia Research 20, 105–115.CrossRefGoogle ScholarPubMed
Simon, AE, Umbricht, D (2010). High remission rates from an initial ultra-high risk state for psychosis. Schizophrenia Research 116, 168–172.CrossRefGoogle ScholarPubMed
Simon, AE, Velthorst, E, Nieman, DH, Linszen, D, Umbricht, D, de Haan, L (2011). Ultra high-risk state for psychosis and non-transition: a systematic review. Schizophrenia Research 132, 8–17.CrossRefGoogle ScholarPubMed
Skrondal, A, Rabe-Hesketh, S (2004). Generalized Latent Variable Modeling: Multilevel, Longitudinal, and Structural Equation Models. CRC Press: Bocca Raton, FL.CrossRefGoogle Scholar
Smieskova, R, Allen, P, Simon, A, Aston, J, Bendfeldt, K, Drewe, J, Gruber, K, Gschwandtner, U, Klarhoefer, M, Lenz, C, Scheffler, K, Stieglitz, RD, Radue, EW, McGuire, P, Riecher-Rossler, A, Borgwardt, SJ (2011). Different duration of at-risk mental state associated with neurofunctional abnormalities. A multimodal imaging study. Human Brain Mapping 33, 2281–2294.CrossRefGoogle ScholarPubMed
Turkington, D, Morrison, AP (2012). Cognitive therapy for negative symptoms of schizophrenia. Archives of General Psychiatry 69, 119–120.CrossRefGoogle ScholarPubMed
van Os, J, Linscott, RJ (2012). The extended psychosis phenotype – relationship with schizophrenia and with ultrahigh risk status for psychosis. Schizophrenia Bulletin 38, 227–230.CrossRefGoogle ScholarPubMed
van Os, J, Linscott, RJ, Myin-Germeys, I, Delespaul, P, Krabbendam, L (2009). A systematic review and meta-analysis of the psychosis continuum: evidence for a psychosis proneness-persistence-impairment model of psychotic disorder. Psychological Medicine 39, 179–195.CrossRefGoogle ScholarPubMed
Velthorst, E, Nieman, DH, Klaassen, RM, Becker, HE, Dingemans, PM, Linszen, DH, de Haan, L (2011). Three-year course of clinical symptomatology in young people at ultra high risk for transition to psychosis. Acta Psychiatrica Scandinavica 123, 36–42.CrossRefGoogle ScholarPubMed
Velthorst, E, Nieman, DH, Linszen, D, Becker, H, de Haan, L, Dingemans, PM, Birchwood, M, Patterson, P, Salokangas, RK, Heinimaa, M, Heinz, A, Juckel, G, von Reventlow, HG, French, P, Stevens, H, Schultze-Lutter, F, Klosterkotter, J, Ruhrmann, S (2010). Disability in people clinically at high risk of psychosis. British Journal of Psychiatry 197, 278–284.CrossRefGoogle ScholarPubMed
Vermunt, JJ, Parkinson, TJ (2002). Claw lameness in dairy cattle: New Zealand-based research. New Zealand Veterinary Journal 50, 88–89.CrossRefGoogle ScholarPubMed
Yung, A, Phillips, LJ, McGorry, P (2004). Treating Schizophrenia in the Prodromal Phase. Taylor & Francis: London.CrossRefGoogle Scholar
Yung, AR, McGorry, PD (1996 a). The initial prodrome in psychosis: descriptive and qualitative aspects. Australian and New Zealand Journal of Psychiatry 30, 587–599.CrossRefGoogle ScholarPubMed
Yung, AR, McGorry, PD (1996 b). The prodromal phase of first-episode psychosis: past and current conceptualizations. Schizophrenia Bulletin 22, 353–370.CrossRefGoogle ScholarPubMed
Yung, AR, Nelson, B, Thompson, A, Wood, SJ (2010). The psychosis threshold in ultra high risk (prodromal) research: is it valid? Schizophrenia Research 120, 1–6.CrossRefGoogle ScholarPubMed
Yung, AR, Phillips, LJ, McGorry, PD, McFarlane, CA, Francey, S, Harrigan, S, Patton, GC, Jackson, HJ (1998). Prediction of psychosis. A step towards indicated prevention of schizophrenia. British Journal of Psychiatry. Supplement 172, 14–20.CrossRefGoogle ScholarPubMed
Yung, AR, Woods, SW, Ruhrmann, S, Addington, J, Schultze-Lutter, F, Cornblatt, BA, Amminger, GP, Bechdolf, A, Birchwood, M, Borgwardt, S, Cannon, TD, de Haan, L, French, P, Fusar-Poli, P, Keshavan, M, Klosterkotter, J, Kwon, JS, McGorry, PD, McGuire, P, Mizuno, M, Morrison, AP, Riecher-Rossler, A, Salokangas, RKR, Seidman, LJ, Suzuki, M, Valmaggia, L, van der Gaag, M, Wood, SJ, McGlashan, TH (2012). Whither the attenuated psychosis syndrome? Schizophrenia Bulletin 38, 1130–1134.CrossRefGoogle ScholarPubMed
Yung, AR, Yuen, HP, Berger, G, Francey, S, Hung, TC, Nelson, B, Phillips, L, McGorry, P (2007). Declining transition rate in ultra high risk (prodromal) services: dilution or reduction of risk? Schizophrenia Bulletin 33, 673–681.CrossRefGoogle ScholarPubMed
Yung, AR, Yuen, HP, McGorry, PD, Phillips, LJ, Kelly, D, Dell'Olio, M, Francey, SM, Cosgrave, EM, Killackey, E, Stanford, C, Godfrey, K, Buckby, J (2005). Mapping the onset of psychosis: the Comprehensive Assessment of At-Risk Mental States. Australian and New Zealand Journal of Psychiatry 39, 964–971.CrossRefGoogle ScholarPubMed