Skip to main content Accessibility help
×
Home

Inter-relationships among psychopathology, premorbid adjustment, cognition and psychosocial functioning in first-episode psychosis: a network analysis approach

  • W. C. Chang (a1) (a2), C. S. M. Wong (a1), P. C. F. Or (a1), A. O. K. Chu (a1), C. L. M. Hui (a1), S. K. W. Chan (a1) (a2), E. M. H. Lee (a1), Y. N. Suen (a1) and E. Y. H. Chen (a1) (a2)...

Abstract

Background

Better understanding of interplay among symptoms, cognition and functioning in first-episode psychosis (FEP) is crucial to promoting functional recovery. Network analysis is a promising data-driven approach to elucidating complex interactions among psychopathological variables in psychosis, but has not been applied in FEP.

Method

This study employed network analysis to examine inter-relationships among a wide array of variables encompassing psychopathology, premorbid and onset characteristics, cognition, subjective quality-of-life and psychosocial functioning in 323 adult FEP patients in Hong Kong. Graphical Least Absolute Shrinkage and Selection Operator (LASSO) combined with extended Bayesian information criterion (BIC) model selection was used for network construction. Importance of individual nodes in a generated network was quantified by centrality analyses.

Results

Our results showed that amotivation played the most central role and had the strongest associations with other variables in the network, as indexed by node strength. Amotivation and diminished expression displayed differential relationships with other nodes, supporting the validity of two-factor negative symptom structure. Psychosocial functioning was most strongly connected with amotivation and was weakly linked to several other variables. Within cognitive domain, digit span demonstrated the highest centrality and was connected with most of the other cognitive variables. Exploratory analysis revealed no significant gender differences in network structure and global strength.

Conclusion

Our results suggest the pivotal role of amotivation in psychopathology network of FEP and indicate its critical association with psychosocial functioning. Further research is required to verify the clinical significance of diminished motivation on functional outcome in the early course of psychotic illness.

Copyright

Corresponding author

Author for correspondence: W. C. Chang, E-mail: changwc@hku.hk

References

Hide All
Addington, D, Addington, J, Maticka-Tyndale, E and Joyce, J (1992) Reliability and validity of a depression rating scale for schizophrenics. Schizophrenia Research 6, 201208.
Alptekin, K, Akvardar, Y, Akdede, BBK, Dumlu, K, Isik, D, Pirincci, F, Yahssin, S and Kitis, A (2005) Is quality of life associated with cognitive impairment in schizophrenia? Progress in Neuro-Psychopharmacology & Biological Psychiatry 29, 239244.
American Psychiatric Association (1994) Diagnostic and Statistical Manual of Mental Disorders, 4th Edn. Washington, DC: American Psychiatric Association.
Andreasen, NC (1984) The Scale for the Assessment of Negative Symptoms (SANS). Iowa City, IA: University of Iowa.
Barrat, A, Barthelemy, M, Pastor-Satorras, R and Vespignani, A (2004) The architecture of complex weighted networks. Proceedings of the National Academy of Sciences of the United States of America 101, 37473752.
Boccaletti, S, Latora, V, Moreno, Y, Chavez, M and Hwang, DU (2006) Complex networks: structure and dynamics. Physics Reports 424, 175308.
Borsboom, D (2017) A network theory of mental disorders. World Psychiatry 16, 513.
Borsboom, D and Cramer, AOJ (2013) Network analysis: an integrative approach to the structure of psychopathology. Annual Review of Clinical Psychology 9, 91121.
Borsboom, D, Fried, E, Epskamp, S, Waldorp, LJ, van Borkulo, CD, van der Maas, HLJ and Cramer, AOJ (2017) False alarm? A comprehensive reanalysis of ‘Evidence that psychopathology system networks have limited replicability’ by Forbes, Wright, Markon, and Krueger (2017). Journal of Abnormal Psychology 126, 989999.
Bowie, CR, Reichenberg, A, Patterson, TL, Heaton, RK and Harvey, PD (2006) Determinants of real-world functional performance in schizophrenia subjects: correlations with cognition, functional capacity, and symptoms. American Journal of Psychiatry 163, 418425.
Cannon-Spoor, HE, Potkin, SG and Wyatt, RJ (1992) Measurement of premorbid adjustment in chronic schizophrenia. Schizophrenia Bulletin 8, 470484.
Chang, WC, Tang, JYM, Hui, CLM, Chiu, CP, Lam, MM, Wong, GH, Chung, DW, Law, CW, Tso, S, Chan, KP, Hung, SF and Chen, EY (2011) Gender differences in patients presenting with first-episode psychosis in Hong Kong: a three-year follow up study. Australian and New Zealand Journal of Psychiatry 45, 199205.
Chang, WC, Tang, JY, Hui, CL, Lam, MM, Chan, SK, Wong, GH, Chiu, CP and Chen, EY (2012) Prediction of remission and recovery in young people presenting with first-episode psychosis in Hong Kong: a 3-year follow-up study. Australian and New Zealand Journal of Psychiatry 46, 100108.
Chang, WC, Cheung, R, Hui, CLM, Lin, J, Chan, SK, Lee, EH and Chen, EY (2015) Rate and risk factors of depressive symptoms in Chinese patients presenting with first-episode non-affective psychosis in Hong Kong. Schizophrenia Research 168, 99105.
Chang, WC, Lau, CFC, Chan, SSI, Hui, CLM, Chan, SKW, Lee, EHM, Lin, J and Chen, EYH (2016 a) Premorbid, clinical and cognitive correlates of primary negative symptoms in first-episode psychosis. Psychiatry Research 242, 144149.
Chang, WC, Hui, CLM, Chan, SKW, Lee, EHM and Chen, EYH (2016 b) Impact of avolition and cognitive impairment on functional outcome in first-episode schizophrenia-spectrum disorder: a prospective one-year follow-up study. Schizophrenia Research 170, 318321.
Chang, WC, Waltz, JA, Gold, JM, Chan, TCW and Chen, EYH (2016 c) Mild reinforcement learning deficits in patients with first-episode psychosis. Schizophrenia Bulletin 42, 14761485.
Chang, WC, Kwong, VWY, Chan, GHK, Jim, OT, Lau, ES, Hui, CL, Chan, SK, Lee, EH and Chen, EY (2017) Prediction of motivational impairment: 12-month follow-up of the randomized-controlled trial on extended early intervention for first-episode psychosis. European Psychiatry 41, 3741.
Chang, WC, Chu, AOK, Kwong, VWY, Wong, CSM, Hui, CLM, Chan, SKW, Lee, EHM and Chen, EYH (2018 a) Patterns and predictors of trajectories for social and occupational functioning in patients presenting with first-episode non-affective psychosis: a three-year follow-up study. Schizophrenia Research 197, 131137.
Chang, WC, Ho, RYH, Tang, JYM, Wong, CSM, Hui, CLM, Chan, SKW, Lee, EMH, Suen, YN and Chen, EYH (2018 b) Early-stage negative symptom trajectories and relationships with 13-year outcomes in first-episode nonaffective psychosis. Schizophrenia Bulletin doi.org/10.1093/schbul/sby115 (Epub ahead of print).
Chang, WC, Kwong, VWY, Or, PCF, Lau, ESK, Chan, GHK, Jim, OTT, Hui, CLM, Chan, SKW, Lee, EHM and Chen, EYH (2018 c) Motivational impairment predicts functional remission in first-episode psychosis: 3-year follow-up of the randomized controlled trial on extended early intervention. Australian and New Zealand Journal of Psychiatry. doi: 10.1177/0004867418758918 (Epub ahead of print).
Chang, WC, Chu, AOK, Treadway, MT, Strauss, GP, Chan, SKW, Lee, EHM, Hui, CLM, Suen, YN and Chen, EYH (2019) Effort-based decision-making impairment in patients with clinically-stabilized first-episode psychosis and its relationship with amotivation and psychosocial functioning. European Neuropsychopharmacology 29, 629642.
Chen, J and Chen, Z (2008) Extended Bayesian information criteria for model selection with large model spaces. Biometrika 95, 759771.
Correll, CU, Galling, B, Pawar, A, Krivko, A, Bonetto, C, Ruggeri, M, Craig, TJ, Nordentoft, M, Srihari, VH, Guloksuz, S, Hui, CLM, Chen, EYH, Valencia, M, Juarez, F, Robinson, DG, Schooler, NR, Brunette, MF, Mueser, KT, Rosenheck, RA, Marcy, P, Addington, J, Estroff, SE, Robinson, J, Penn, D, Severe, JB and Kane, JM (2018) Comparison of early intervention services vs treatment as usual for early-phase psychosis: a systematic review, meta-analysis, and meta-regression. JAMA Psychiatry 75, 555565.
Cotton, SM, Lambert, M, Schimmelmann, BG, Foley, DL, Morley, KI, McGorry, PD and Conus, P (2009) Gender differences in premorbid, entry, treatment, and outcome characteristics in a treated epidemiological sample of 661 patients with first episode psychosis. Schizophrenia Research 114, 1724.
Dickinson, D, Ramsey, MB and Gold, JM (2007) Overlooking the obvious: a meta-analytic comparison of digit symbol coding tasks and other cognitive measures in schizophrenia. Archives of General Psychiatry. 64, 111.
Emsley, R, Rabinowitz, J, Torreman, M and Group R-I-EPGW (2003) The factor structure for the Positive and Negative Syndrome Scale (PANSS) in recent-onset psychosis. Schizophrenia Research 61, 4757.
Epskamp, S and Fried, EI (2018) A tutorial on regularized partial correlation networks. Psychological Methods 23, 617634.
Epskamp, S, Cramer, AO, Waldorp, LJ, Schmittmann, VD and Borsboom, D (2012) Qgraph: network visualizations of relationships in psychometric data. Journal of Statistical Software 48, 118.
Epskamp, S, Borsboom, D and Fried, EI (2018 a) Estimating psychological networks and their accuracy: a tutorial paper. Behavior Research Methods 50, 195212.
Epskamp, S, van Borkulo, CD, van der Veen, DC, Servaas, MN, Isvoranu, AM, Riese, H and Cramer, AOJ (2018 b) Personalized network modeling in psychopathology: the importance of contemporaneous and temporal connections. Clinical Psychological Science 6, 41427.
Fervaha, G, Foussias, G, Agid, O and Remington, G (2015) Motivational deficits in early schizophrenia: prevalent, persistent, and key determinants of functional outcome. Schizophrenia Research 166, 916.
Forbes, NF, Carrick, LA, McIntosh, AM and Lawrie, SM (2009) Working memory in schizophrenia: a meta-analysis. Psychological Medicine 39, 899905.
Forbes, MK, Wright, AGC, Markon, KE and Krueger, RF (2017 a) Evidence that psychopathology symptom networks have limited replicability. Journal of Abnormal Psychology 126, 969988.
Forbes, MK, Wright, AGC, Markon, KE, Krueger, RF (2017 b) Further evidence that psychopathology networks have limited replicability and utility: response to Borsboom et al. (2017) and Steinley et al. (2017). Journal of Abnormal Psychology 126, 10111016.
Foussias, G, Mann, S, Zakzanis, KK, van Reekum, R and Remington, G (2009) Motivational deficits as the central link to functioning in schizophrenia: a pilot study. Schizophrenia Research 115, 333337.
Foygel, R and Drton, M (2010) Extended Bayesian information criteria for Gaussian graphical models. Advances in Neural Information Processing Systems 23, 20202028.
Fried, EI, van Borkulo, CD, Cramer, AOJ, Boschloo, L, Schoevers, RA and Borsboom, D (2017) Mental disorders as networks of problems: a review of recent insights. Social Psychiatry and Psychiatric Epidemiology 52, 110.
Friedman, J, Hastie, T and Tibshirani, R (2008) Sparse inverse covariance estimation with graphical lasso. Biostatistics (Oxford, England) 9, 432441.
Fruchterman, TMJ and Reingold, EM (1991) Graph drawing by force-directed placement. Software: Practice and Experience 22, 11291164.
Galderisi, S, Rucci, P, Kirkpatrick, B, Mucci, A, Gibertoni, D, Rocca, P, Rossi, A, Bertolino, A, Strauss, GP, Aguglia, E, Bellomo, A, Murri, MB, Bucci, P, Carpiniello, B, Comparelli, A, Cuomo, A, De Berardis, D, Dell'Osso, L, Di Fabio, F, Gelao, B, Marchesi, C, Monteleone, P, Montemagni, C, Orsenigo, G, Pacitti, F, Roncone, R, Santonastaso, P, Siracusano, A, Vignapiano, A, Vita, A, Zeppegno, P, Maj, M and Italian Network for Research on Psychoses (2018). Interplay among psychopathologic variables, personal resources, context-related factors, and real-life functioning in individuals with schizophrenia: a network analysis. JAMA Psychiatry 75, 396404.
Global Burden of Disease Study 2013 Collaborators (2015) Global, regional, and national incidence, prevalence, and years lived with disability for 301 acute and chronic diseases and injuries in 188 countries, 1990–2013: a systematic analysis for the Global Burden of Disease Study 2013. Lancet 386, 743800.
Gold, JM, Waltz, JA and Frank, MJ (2015) Effort cost computation in schizophrenia: a commentary on the recent literature. Biological Psychiatry 78, 747753.
Goodman, SH, Sewell, DR, Cooley, EL and Leavitt, N (1993) Assessing levels of adaptive functioning: the Role Functioning Scale. Community Mental Health Journal 29, 119131.
Häfner, H, Riecher-Rössler, A, Hambrecht, M, Maurer, K, Meissner, S, Schmidtke, A, Fätkenheuer, B, Löffler, W and van der Heiden, W (1992) IRAOS: an instrument for the assessment of onset and early course of schizophrenia. Schizophrenia Research 6, 209223.
Hasson-Ohayon, I, Goldzweig, G, Lavi-Rotenberg, A, Luther, L and Lysaker, P (2018) The centrality of cognitive symptoms and metacognition within the interacting network of symptoms, neurocognition, social cognition and metacognition in schizophrenia. Schizophrenia Research 202, 260266.
Hong Kong Psychological Society (1989 a) The Wechsler Adult Intelligence Scale-Revised (Cantonese version). Hong Kong: Hong Kong Psychological Society.
Hong Kong Psychological Society (1989 b) The Wechsler Adult Memory Scale-Revised (Cantonese version). Hong Kong: Hong Kong Psychological Society.
Hui, CLM, Chang, WC, Chan, SKW, Lee, EH, Tam, WW, Lai, DC, Wong, GH, Tang, JY, Li, FW, Leung, KF, McGhee, SM, Sham, PC and Chen, EY (2014) Early intervention and evaluation for adult-onset psychosis: the JCEP study rationale and design. Early Intervention in Psychiatry 8, 261268.
Hui, CLM, Lau, WWY, Leung, CM, Chang, WC, Tang, JY, Wong, GH, Chan, SK, Lee, EH and Chen, EY (2015) Clinical and social correlates of duration of untreated psychosis among adult-onset psychosis in Hong Kong Chinese: the JCEP study. Early Intervention in Psychiatry 9, 118125.
Isvoranu, AM, Boyette, LL, Guloksuz, S and Borsboom, D (2017 a) Chapter G1. Symptoms network models of psychosis. In Tamminga, CA, Ivleva, EI, Reininghaus, U and van Os, J (eds), Dimensions of Psychosis. Oxford University Press. doi: 10.17605/OSF.IO/NK8YV (in press).
Isvoranu, AM, van Borkulo, CD, Boyette, LL, Wigman, JTW, Vinkers, CH, Borsboom, D and GROUP Investigators (2017 b) A network approach to psychosis: pathways between childhood trauma and psychotic symptoms. Schizophrenia Bulletin 43, 187196.
Jin, H and Mosweu, I (2017) The societal cost of schizophrenia: a systematic review. Pharmacoeconomics 35, 2542.
Kay, SR, Fiszbein, A and Opler, LA (1987) The positive and negative syndrome scale (PANSS) for schizophrenia. Schizophrenia Bulletin 13, 261276.
Kirkpatrick, B, Fenton, WS, Carpenter, WT Jr and Marder, SR (2006) The NIMH-MATRICS consensus development statement on negative symptoms. Schizophrenia Bulletin 32, 214219.
Klippel, A, Wiechtbauer, W, Reininghaus, U, Wigman, J, van Borkulo, C, Myin-Germeys, I and Wichers, M (2018) The cascade of stress: a network approach to explore differential dynamics in populations varying in risk for psychosis. Schizophrenia Bulletin 44, 328337.
Konstantakopoulos, G, Ploumpidis, D, Oulis, P, Patrikelis, P, Soumani, A, Papadimitriou, GN and Politis, AM (2011) Apathy, cognitive deficits and functional impairment in schizophrenia. Schizophrenia Research 133, 193198.
Kwong, VWY, Chang, WC, Chan, GHK, Jim, OT, Lau, ES, Hui, CL, Chan, SK, Lee, EH and Chen, EY (2017) Clinical and treatment-related determinants of subjective quality of life in patients with first-episode psychosis. Psychiatry Research 249, 3945.
Lally, J, Ajnakina, O, Stubbs, B, Cullinane, M, Murphy, KC, Gaughran, F and Murray, RM (2017) Remission and recovery from first-episode psychosis in adults: systematic review and meta-analysis of long-term outcome studies. British Journal of Psychiatry 211, 350358.
Levine, SZ and Leucht, S (2016) Identifying a system of predominant negative symptoms: network analysis of three randomized clinical trials. Schizophrenia Research 178, 1722.
Liemburg, E, Castelein, S, Stewart, R, van der Gaag, M, Aleman, A, Knegtering, H and Genetic Risk and Outcome of Psychosis (GROUP) Investigators (2013) Two subdomains of negative symptoms in psychotic disorders: established and confirmed in two large cohorts. Journal of Psychiatric Research 47, 718725.
Liu, H, Lafferty, J and Wasserman, L (2009) The nonparanormal: semiparametric estimation of high dimensional undirected graphs. Journal of Machine Learning Research 10, 22952328.
Lutgens, D, Joober, R, Iyer, S, Lepage, M, Norman, R, Schmitz, N, Mustafa, S, Abadi, S and Malla, A (2019) Progress of negative symptoms over the initial 5 years of a first episode of psychosis. Psychological Medicine 49, 6674.
McNally, RJ (2016) Can network analysis transform psychopathology? Behaviour Research and Therapy 86, 95104.
Messinger, JW, Tremeau, F and Antonius, D (2011) Avolition and expressive deficits capture negative symptom phenomenology: implications for DSM-5 and schizophrenia research. Clinical Psychology Review 31, 161168.
Nelson, HE (1976) A modified card sorting test sensitive to frontal lobe defects. Cortex 12, 313324.
Ochoa, S, Usall, J, Cobo, J, Labad, X and Kulkarni, J (2012). Gender differences in schizophrenia and first-episode psychosis: a comprehensive literature review. Schizophrenia Research and Treatment. 916198.
Opsahl, T, Agneessens, F and Skvoretz, J (2010) Node centrality in weighted networks generalizing degree and shortest paths. Social Networks 32, 245251.
Penttilä, M, Jääskeläinen, E, Hirvonen, N, Isohanni, M and Miettunen, J (2014) Duration of untreated psychosis as predictor of long-term outcome in schizophrenia: systematic review and meta-analysis. British Journal of Psychiatry 205, 8894.
R Core Team (2018) R: A Language and Environment for Statistical Computing. Vienna, Austria: R Foundation for Statistical Computing. Available at http://www.R-project.org/.
Renwick, L, Jackson, D, Foley, S, Owens, E, Ramperti, N, Behan, C, Anwar, M, Kinsella, A, Turner, N, Clarke, M and O'Callaghan, E (2012) Depression and quality of life in first-episode psychosis. Comprehensive Psychiatry 53, 451455.
Ritsner, MS (2007) Predicting quality of life impairment in chronic schizophrenia from cognitive variables. Quality of Life Research 16, 929937.
Russo, M, Levine, SZ, Demjaha, A, Di Forti, M, Bonaccorso, S, Fearon, P, Dazzan, P, Pariante, CM, David, AS, Morgan, C, Murray, RM and Reichenberg, A (2014) Association between symptom dimensions and categorical diagnoses of psychosis: a cross-sectional and longitudinal investigation. Schizophrenia Bulletin 40, 111119.
Savla, GN, Vella, L, Armstrong, CC, Penn, DL and Twamley, EW (2013) Deficits in domains of social cognition in schizophrenia: a meta-analysis of the empirical evidence. Schizophrenia Bulletin 39, 979992.
So, E, Kam, I, Leung, CM, D, Chung, Liu, Z and Fong, S (2003) The Chinese-bilingual SCID-I/P Project: Stage 1: reliability for mood disorders and schizophrenia. Hong Kong Journal of Psychiatry 13, 718.
Steinly, D, Hoffman, M, Brusco, MJ and Sher, KJ (2017) A method for making inferences in network analysis: comment on Forbes, Wright, Markon, and Krueger (2017). Journal of Abnormal Psychology 126, 10001010.
Strauss, GP and Gold, JM (2016) A psychometric comparison of the clinical assessment interview for negative symptoms and the brief negative symptom scale. Schizophrenia Bulletin 42, 13841394.
Strauss, GP, Horan, WP, Kirkpatrick, B, Fischer, BA, Keller, WR, Miski, P, Buchanan, RW, Green, MF and Carpenter, WT Jr (2013) Deconstructing negative symptoms of schizophrenia: avolition-apathy and diminished expression clusters predict clinical presentation and functional outcome. Journal of Psychiatric Research 47, 783790.
Strauss, GP, Waltz, JA and Gold, JM (2014) A review of reward processing and motivational impairment in schizophrenia. Schizophrenia Bulletin 40(suppl. 2), 107116.
Strauss, GP, Esfahlani, FZ, Galderisi, S, Mucci, A, Rossi, A, Bucci, P, Rocca, P, Maj, M, Kirkpatrick, B, Ruiz, I and Sayama, H (2018 a) Network analysis reveals the latent structure of negative symptoms in schizophrenia. Schizophrenia Bulletin. doi: 10.1093/schbul/sby133 (Epub ahead of print).
Strauss, GP, Nunez, A, Ahmed, AO, Barchard, KA, Granholm, E, Kirkpatrick, B, Gold, JM and Allen, DN (2018 b) The latent structure of negative symptoms in schizophrenia. JAMA Psychiatry 75, 12711279.
Thorup, A, Albert, N, Bertelsen, M, Petersen, L, Jeppesen, P, Le Quack, P, Krarup, G, Jørgensen, P and Nordentoft, M (2014) Gender differences in first-episode psychosis at 5-year follow-up – two different courses of disease? Results from the OPUS study at 5-year follow-up. European Psychiatry 29, 4451.
Tolman, AW and Kurtz, MM (2012) Neurocognitive predictors of objective and subjective quality of life in individuals with schizophrenia: a meta-analytic investigation. Schizophrenia Bulletin 38, 304315.
van Borkulo, C (2016) Package NetworkComparisonTest. Available at http://cran.r-project.org.
van Borkulo, C, Boschloo, L, Kossakowski, J, Tio, P, Schoevers, R, Borsboom, D and Waldorp, L (2017) Comparing network structures on three aspects: A permutation test. Available at http://dx.doi.org/10.13140/RG.2.2.29455.38569.
van Rooijen, G, Isvoranu, AM, Meijer, C, van Borkulo, CD, Ruhe, HG, de Haan, L and GROUP investigators (2017) A symptom network structure of the psychosis spectrum. Schizophrenia Research 189, 7593.
van Rooijen, G, Isvoranu, AM, Kruijt, OH, van Borkulo, CD, Meijer, CJ, Wigman, JTW, Ruhé, HG, de Haan, L and GROUP investigators (2018) A state-independent network of depressive, negative and positive symptoms in male patients with schizophrenia spectrum disorders. Schizophrenia Research 193, 232239.
Ventura, J, Subotnik, KL, Giltlin, MJ, Gretchen-Doorly, D, Ered, A, Villa, KF, Hellemann, GS and Nuechterlein, KH (2015) Negative symptoms and functioning during the first year after a recent onset of schizophrenia and 8 years later. Schizophrenia Research 161, 407413.
Verma, S, Subramaniam, M, Abdin, E, Poon, LY and Chong, SA (2012) Symptomatic and functional remission in patients with first-episode psychosis. Acta Psychiatrica Scandinavica 126, 282289.
Ware, JE, Kosinski, M and Keller, SD (1996) A 12-item short-form health survey: construction of scales and preliminary tests of reliability and validity. Medical Care 34, 220233.
Woon, PS, Chia, MY, Chan, WY and Sim, K (2010) Neurocognitive, clinical and functional correlates of subjective quality of life in Asian outpatients with schizophrenia. Progress in Neuro-Psychopharmacology & Biological Psychiatry 34, 463468.

Keywords

Type Description Title
WORD
Supplementary materials

Chang et al. supplementary material
Chang et al. supplementary material 1

 Word (758 KB)
758 KB

Metrics

Full text views

Total number of HTML views: 0
Total number of PDF views: 0 *
Loading metrics...

Abstract views

Total abstract views: 0 *
Loading metrics...

* Views captured on Cambridge Core between <date>. This data will be updated every 24 hours.

Usage data cannot currently be displayed