Hostname: page-component-cd9895bd7-8ctnn Total loading time: 0 Render date: 2024-12-25T16:30:02.512Z Has data issue: false hasContentIssue false
  • English
  • Français

Comorbidity: A network perspective

Published online by Cambridge University Press:  29 June 2010

Angélique O. J. Cramer ,
Lourens J. Waldorp ,
Han L. J. van der Maas  and
Denny Borsboom
Angélique O. J. Cramer
Affiliation:
Department of Psychology, University of Amsterdam, 1018 WB Amsterdam, The [email protected]
Lourens J. Waldorp
Affiliation:
Department of Psychology, University of Amsterdam, 1018 WB Amsterdam, The [email protected]://users.fmg.uva.nl/lwaldorp
Han L. J. van der Maas
Affiliation:
Department of Psychology, University of Amsterdam, 1018 WB Amsterdam, The [email protected]://users.fmg.uva.nl/hvandermaas/
Denny Borsboom
Affiliation:
Department of Psychology, University of Amsterdam, 1018 WB Amsterdam, The [email protected]://sites.google.com/site/borsboomdenny/dennyborsboom
Get access Rights & Permissions [Opens in a new window]

Abstract

The pivotal problem of comorbidity research lies in the psychometric foundation it rests on, that is, latent variable theory, in which a mental disorder is viewed as a latent variable that causes a constellation of symptoms. From this perspective, comorbidity is a (bi)directional relationship between multiple latent variables. We argue that such a latent variable perspective encounters serious problems in the study of comorbidity, and offer a radically different conceptualization in terms of a network approach, where comorbidity is hypothesized to arise from direct relations between symptoms of multiple disorders. We propose a method to visualize comorbidity networks and, based on an empirical network for major depression and generalized anxiety, we argue that this approach generates realistic hypotheses about pathways to comorbidity, overlapping symptoms, and diagnostic boundaries, that are not naturally accommodated by latent variable models: Some pathways to comorbidity through the symptom space are more likely than others; those pathways generally have the same direction (i.e., from symptoms of one disorder to symptoms of the other); overlapping symptoms play an important role in comorbidity; and boundaries between diagnostic categories are necessarily fuzzy.

Keywords

comorbiditycomplex networksgeneralized anxietylatent variable modelsmajor depression
Type
Target Article
Information
Behavioral and Brain Sciences , Volume 33 , Issue 2-3 , June 2010 , pp. 137 - 150
Copyright
Copyright © Cambridge University Press 2010

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Achermann, P. (2004) The two-process model of sleep regulation revisited. Aviation, Space, and Environmental Medicine 75:A37–43.Google ScholarPubMed
Aggen, S. H., Neale, M. C. & Kendler, K. S. (2005) DSM criteria for major depression: Evaluating symptom patterns using latent-trait item response models. Psychological Medicine 35:475–87.CrossRefGoogle ScholarPubMed
Agresti, A. (2002) Categorical data analysis. Wiley.CrossRefGoogle Scholar
Albert, R. & Barabási, A.-L. (1999) Emergence of scaling in random networks. Science 286:509–12.Google Scholar
Albert, R. & Barabási, A.-L. (2002) Statistical mechanics of complex networks. Reviews of Modern Physics 74:47–97.CrossRefGoogle Scholar
Albert, U., Rosso, G., Maina, G. & Bogetto, F. (2008) Impact of anxiety disorder comorbidity on quality of life in euthymic bipolar disorder patients: Differences between bipolar I and II subtypes. Journal of Affective Disorders 105:297–303.CrossRefGoogle ScholarPubMed
Alligood, K. T., Sauer, T. & Yorke, J. A. (1997) Chaos: An introduction to dynamical systems. Springer.CrossRefGoogle Scholar
American Psychiatric Association (APA). (1994) Diagnostic and statistical manual of mental disorders, 4th edition, (DSM-IV). American Psychiatric Association/APA Books.Google Scholar
Andersen, E. B. (1973) Sufficient statistics and latent trait models. Psychometrika 42:69–81.CrossRefGoogle Scholar
Anderson, J. C., Williams, S., McGee, R. & Silva, P. A. (1987) DSM-III disorders in preadolescent children: Prevalence in a large sample from the general population. Archives of General Psychiatry 44:69–77.Google Scholar
Angold, A., Costello, E. J. & Erkanli, A. (1999) Comorbidity. Journal of Child Psychology and Psychiatry 40:57–87.CrossRefGoogle ScholarPubMed
Barlow, D. H., Allen, L. B. & Choate, M. L. (2004) Toward a unified treatment for emotional disorders. Behavior Therapy 35:205–30.CrossRefGoogle Scholar
Barrat, A. & Weigt, M. (2000) On the properties of small-world network models. European Physical Journal B 13:547–60.Google Scholar
Beck, A. T., Rush, A. J., Shaw, B. F. & Emery, G. (1979) Cognitive therapy of depression. Guilford Press.Google Scholar
Biederman, J., Faraone, S., Mick, E. & Lelon, E. (1995) Psychiatric comorbidity among referred juveniles with major depression: Fact or artifact? Journal of the American Academy of Child and Adolescent Psychiatry 34:579–90.CrossRefGoogle ScholarPubMed
Bleich, A., Koslowsky, M., Dolev, A. & Lerer, B. (1997) Post-traumatic stress disorder and depression: An analysis of comorbidity. British Journal of Psychiatry 170:479–82.CrossRefGoogle ScholarPubMed
Boccaletti, S., Latora, V., Moreno, Y., Chavez, M. & Hwang, D.-U. (2006) Complex networks: Structure and dynamics. Physics Reports 424:175–308.CrossRefGoogle Scholar
Bollen, K. A. (1989) Structural equations with latent variables. Wiley.Google Scholar
Bollen, K. A. (2002) Latent variables in psychology and the social sciences. Annual Review of Psychology 53:605–34.Google Scholar
Boomsma, D. I., Busjahn, A. & Peltonen, L. (2002) Classical twin studies and beyond. Nature Reviews: Genetics 3:872–82.CrossRefGoogle ScholarPubMed
Borbély, A. A. & Achermann, P. (1999) Sleep homeostasis and models of sleep regulation. Journal of Biological Rhythms 14:559–68.Google ScholarPubMed
Borsboom, D. (2002) The structure of the DSM [Letter to the editor]. Archives of General Psychiatry 59:569–70.CrossRefGoogle ScholarPubMed
Borsboom, D. (2005) Measuring the mind: Conceptual issues in contemporary psychometrics. Cambridge University Press.Google Scholar
Borsboom, D. (2008) Psychometric perspectives on diagnostic systems. Journal of Clinical Psychology 64:1089–108.CrossRefGoogle ScholarPubMed
Borsboom, D., Mellenbergh, G. J. & Van Heerden, J. (2003) The theoretical status of latent variables. Psychological Review 110:203–19.Google Scholar
Borsboom, D., Mellenbergh, G. J. & Van Heerden, J. (2004) The concept of validity. Psychological Review 111:1061–71.CrossRefGoogle ScholarPubMed
Boyd, J. H., Burke, J. D., Gruenberg, E., Holzer, C. E., Rae, D. S., George, L. K., Karno, M., Stoltzman, R., McEvoy, L. & Nestadt, G. (1984) Exclusion criteria of DSM-III: A study of co-occurrence of hierarchy-free syndromes. Archives of General Psychiatry 41:983–89.Google Scholar
Brown, T. A., Antony, M. M. & Barlow, D. H. (1995) Diagnostic comorbidity in panic disorder: Effect on treatment outcome and course of comorbid diagnoses following treatment. Journal of Consulting and Clinical Psychology 63:408–18.CrossRefGoogle ScholarPubMed
Brown, T. A. & Barlow, D. H. (1992) Comorbidity among anxiety disorders: Implications for treatment and DSM-IV . Journal of Consulting and Clinical Psychology 60:835–44.CrossRefGoogle ScholarPubMed
Brown, T. A., Campbell, L. A., Lehman, C. L., Grisham, J. R. & Mancill, R. B. (2001) Current and lifetime comorbidity of the DSM-IV anxiety and mood disorders in a large clinical sample. Journal of Abnormal Psychology 110:585–99.CrossRefGoogle Scholar
Brown, T. A., Chorpita, B. F. & Barlow, D. H. (1998) Structured relationships among dimensions of the DSM-IV anxiety and mood disorders and dimensions of negative affect, positive affect, and autonomic arousal. Journal of Abnormal Psychology 107:179–92.Google Scholar
Carter, R. M., Wittchen, H.-U., Pfister, H. & Kessler, R. C. (2001) One-year prevalence of subthreshold and threshold DSM-IV generalized anxiety disorder in a nationally representative sample. Depression and Anxiety 13:78–88.CrossRefGoogle Scholar
Cervone, D. (2004) The architecture of personality. Psychological Review 111:183–204.Google Scholar
Cilliers, P. (1998) Complexity and postmodernism. Routledge.Google Scholar
Clark, L. A. & Watson, D. (1991) Tripartite model of anxiety and depression: Psychometric evidence and taxonomic implications. Journal of Abnormal Psychology 100:316–36.CrossRefGoogle ScholarPubMed
Clark, L. A., Watson, D. & Reynolds, S. (1995) Diagnosis and classification of psychopathology: Challenges to the current system and future directions. Annual Review of Psychology 46:121–53.CrossRefGoogle Scholar
Csárdi, G. & Nepusz, T. (2006) The igraph software package for complex network research. International Journal of Complex Systems 1695.Google Scholar
David, M., Ceschi, G., Billieux, J. & Van der Linden, M. (2008) Depressive symptoms after trauma: Is self-esteem a mediating factor? Journal of Nervous and Mental Disease 196:735–42.CrossRefGoogle ScholarPubMed
De Berg, M., Cheong, O., Van Kreveld, M. & Overmars, M. (2008) Computational geometry: Algorithms and applications. Springer.Google Scholar
Dethlefsen, D. & Hojsgaard, S. (2005) A common platform for graphical models in R: The gRbase package. Journal of Statistical Software 15:1–12.Google Scholar
DiBattista, G., Eades, P., Tamassia, R. & Tollis, I. G. (1994) Algorithms for drawing graphs: An annotated bibliography. Computational Geometry: Theory and Applications 4:235–82.CrossRefGoogle Scholar
Finelli, L. A., Baumann, H., Borbély, A. A. & Achermann, P. (2000) Dual electroencephalogram markers of human sleep homeostasis: Correlation between theta activity in waking and slow-wave activity in sleep. Neuroscience 101:523–29.CrossRefGoogle ScholarPubMed
Franklin, C. L. & Zimmerman, M. (2001) Posttraumatic stress disorder and major depressive disorder: Investigating the role of overlapping symptoms in diagnostic comorbidity. Journal of Nervous and Mental Disease 189:548–51.CrossRefGoogle ScholarPubMed
Gotlib, I. H., Lewinsohn, P. M. & Seeley, J. R. (1995) Symptoms versus a diagnosis of depression: Differences in psychosocial functioning. Journal of Consulting and Clinical Psychology 63:90–100.Google Scholar
Grayson, D. A. (1988) Two-group classification in latent trait theory: Scores with monotone likelihood ratio. Psychometrika 53:383–92.CrossRefGoogle Scholar
Haig, B. D. (2005) An abductive theory of scientific method. Psychological Methods 10:371–88.CrossRefGoogle ScholarPubMed
Hamaker, E. L., Nesselroade, J. R. & Molenaar, P. C. M. (2007) The integrated state-trait model. Journal of Research in Personality 41:295–315.CrossRefGoogle Scholar
Hartman, C. A., Hox, J., Mellenbergh, G. J., Boyle, M. H., Offord, D. R., Racine, Y., McNamee, J., Gadow, K. D., Sprafkin, J., Kelly, K. L., Nolan, E. E., Tannock, R., Schachar, R., Schut, H., Postma, I., Drost, R. & Sergeant, J. A. (2001) DSM-IV internal construct validity: When a taxonomy meets data. Journal of Child Psychology and Psychiatry 42:817–36.CrossRefGoogle Scholar
Haslam, N. (2000) Psychiatric categories as natural kinds: Essentialist thinking about mental disorders. Social Research 67:1031–58.Google Scholar
Haslam, N. & Ernst, D. (2002) Essentialist beliefs about mental disorders. Journal of Social and Clinical Psychology 21:628–44.CrossRefGoogle Scholar
Herman, I. (2000) Graph visualization and navigation in information visualization: A survey. IEEE Transactions on Visualization and Computer Graphics 6:24–43.CrossRefGoogle Scholar
Hirshfeld, D. R., Rosenbaum, J. F., Biederman, J., Bolduc, E. A., Faraone, S. V., Snidman, N., Reznick, J. S. & Kagan, J. (1992) Stable behavioral inhibition and its association with anxiety disorder. Journal of the American Academy of Child and Adolescent Psychiatry 31:103–11.CrossRefGoogle ScholarPubMed
Hood, S. B. (2008) Latent variable realism in psychometrics. Unpublished doctoral dissertation, Indiana University.Google Scholar
Hubert, L. J. (1974) Some applications of graph theory to clustering. Psychometrika 39:283–309.Google Scholar
Jablensky, A. (2007) Does psychiatry need an overarching concept of “mental disorder”? World Psychiatry 6:157–58.Google ScholarPubMed
Kamphuis, J. H. & Telch, M. J. (2000) Effects of distraction and guided threat reappraisal on fear reduction during exposure-based treatments for specific fears. Behaviour Research and Therapy 38:1163–81.Google Scholar
Kashani, J. H., Beck, N. C., Hoeper, E. W., Fallahi, C., Corcoran, C. M., McAllister, J. A., Rosenberg, T. K. & Reid, J. C. (1987) Psychiatric disorders in a community sample of adolescents. American Journal of Psychiatry 144:584–89.Google Scholar
Kendell, R. E. (1975) The concept of disease and its implications for psychiatry. British Journal of Psychiatry 127:305–15.CrossRefGoogle ScholarPubMed
Kendler, K. S., Gardner, C. O., Neale, M. C. & Prescott, C. A. (2001) Genetic risk factors for major depression in men and women: Similar or distinct heritabilities and same or partly distinct genes. Psychological Medicine 31:605–16.Google Scholar
Kessler, R. C. (1997) The effects of stressful life events on depression. Annual Review of Psychology 48:191–214.Google Scholar
Kessler, R. C., Berglund, P., Chiu, W. T., Demler, O., Heeringa, S., Hiripi, E., Jin, R., Pennell, B. E., Walters, E. E., Zaslavsky, A. & Zheng, H. (2004) The US National Comorbidity Survey Replication (NCS-R): Design and field procedures. International Journal of Methods in Psychiatric Research 13:69–92.CrossRefGoogle ScholarPubMed
Kessler, R. C., Berglund, P., Demler, O., Jin, R. & Walters, E. E. (2005a) Lifetime prevalence and age-of-onset distributions of DSM-IV disorders in the National Comorbidity Survey Replication. Archives of General Psychiatry 62:593–602.Google Scholar
Kessler, R. C., Chiu, W. T., Demler, O. & Walters, E. E. (2005b) Prevalence, severity, and comorbidity of 12-month DSM-IV disorders in the National Comorbidity Survey Replication. Archives of General Psychiatry 62:617–27.CrossRefGoogle ScholarPubMed
Kessler, R. C., DuPont, R. L., Berglund, P. & Wittchen, H.-U. (1999) Impairment in pure and comorbid generalized anxiety disorder and major depression at 12 months in two national surveys. American Journal of Psychiatry 156:1915–23.CrossRefGoogle ScholarPubMed
Kessler, R. C., McGonagle, K. A., Zhao, S., Nelson, C. B., Hughes, M., Eshleman, S., Wittchen, H. U. & Kendler, K. S. (1994) Lifetime and 12-month prevalence of DSM-III-R psychiatric disorders in the United States: Results from the National Comorbidity Survey. Archives of General Psychiatry 51:8–19.Google Scholar
Kessler, R. C. & Ustun, T. B. (2004) The World Mental Health (WMH) survey initiative version of the World Health Organization (WHO) Composite International Diagnostic Interview (CIDI). International Journal of Methods in Psychiatric Research 13:93–121.CrossRefGoogle ScholarPubMed
Kim, N. S. & Ahn, W.-K. (2002) Clinical psychologists' theory-based representations of mental disorders predict their diagnostic reasoning and memory. Journal of Experimental Psychology: General 131:451–76.CrossRefGoogle ScholarPubMed
Klein, D. F. (1978) A proposed definition of mental disorder. In: Critical issues in psychiatric diagnosis, ed. Klein, D. F. & Spitzer, R. L., pp. 41–72. Raven Press.Google Scholar
Krichel, T. & Bakkalbasi, N. (2006) A social network analysis of research collaboration in the economics community. Journal of Information Management and Scientometrics 3:1–12.Google Scholar
Krueger, R. F. (1999) The structure of common mental disorders. Archives of General Psychiatry 56:921–26.Google Scholar
Krueger, R. F. & Markon, K. E. (2006b) Understanding psychopathology: Melding behavior genetics, personality, and quantitative psychology to develop an empirically based model. Current Directions in Psychological Science 15:113–17.Google Scholar
Lilienfeld, S. O. & Marino, L. (1999) Essentialism revisited: Evolutionary theory and the concept of mental disorder. Journal of Abnormal Psychology 108:400–11.Google Scholar
Lord, F. M. & Novick, M. R. (1968) Statistical theories of mental test scores. Addison-Wesley.Google Scholar
Low, N. C. P., Cui, L. & Merikangas, K. R. (2008) Specificity of familial transmission of anxiety and comorbid disorders. Journal of Psychiatric Research 42:596–604.Google Scholar
Maier, W., Gänsicke, M. & Weiffenbach, O. (1997) The relationship between major and subthreshold variants of unipolar depression. Journal of Affective Disorders 45:41–51.Google Scholar
Markus, K. A. (2008) Hypothesis formulation, model interpretation, and model equivalence: Implications of a mereological causal interpretation of structural equation models. Multivariate Behavioral Research 43:177–209.Google Scholar
Masters, G. N. & Wright, B. D. (1984) The essential process in a family of measurement models. Psychometrika 49:529–44.CrossRefGoogle Scholar
McCrae, R. R. & Costa, P. T. Jr. (2008) Empirical and theoretical status of the Five-Factor Model of personality traits. In: Sage handbook of personality theory and assessment, vol. 1, ed. Boyle, G., Matthews, G. & Saklofske, D., pp. 273–94. Sage.CrossRefGoogle Scholar
McGrath, R. E. (2005) Conceptual complexity and construct validity. Journal of Personality Assessment 85:112–24.CrossRefGoogle ScholarPubMed
McGue, M. & Christensen, K. (2003) The heritability of depression symptoms in elderly Danish twins: Occasion-specific versus general effects. Behavior Genetics 33:83–93.CrossRefGoogle ScholarPubMed
McNally, R. J. (1994) Panic disorder: A critical analysis. Guilford.Google Scholar
McNiel, J. M. & Fleeson, W. (2006) The causal effects of extraversion on positive affect and neuroticism on negative affect: Manipulating state extraversion and state neuroticism in an experimental approach. Journal of Research in Personality 40:529–50.CrossRefGoogle Scholar
Merikangas, K. R., Mehta, R. L., Molnar, B. E., Walters, E. E., Swendsen, J. D., Aguilar-Gaziola, S., Bijl, R., Borges, G., Caraveo-Anduaga, J. J., Dewit, D. J., Kolody, B., Vega, W. A., Wittchen, H.-U. & Kessler, R. C. (1998) Comorbidity of substance use disorders with mood and anxiety disorders: Results of the International Consortium in Psychiatric Epidemiology. Addictive Behaviors 23:893–907.Google Scholar
Michell, J. (2005) The logic of measurement: A realist overview. Measurement 38:285–94.Google Scholar
Mineka, S., Watson, D. W. & Clark, L. A. (1998) Psychopathology: Comorbidity of anxiety and unipolar mood disorders. Annual Review of Psychology 49:377–412.CrossRefGoogle Scholar
Moffitt, T. E., Harrington, H., Caspi, A., Kim-Cohen, J., Goldberg, D., Gregory, A. M. & Poulton, R. (2007) Depression and generalized anxiety disorder: Cumulative and sequential comorbidity in a birth cohort followed prospectively to age 32 years. Archives of General Psychiatry 64:651–60.CrossRefGoogle Scholar
Molenaar, P. C. M. (2003) State space techniques in structural equation modeling: Transformation of latent variables in and out of latent variable models. Unpublished manuscript, University of Amsterdam. Available at: http://www.hhdev.psu.edu/hdfs/faculty/docs/StateSpaceTechniques.pdf.Google Scholar
Molenaar, P. C. M. (2004) A manifesto on psychology as idiographic science: Bringing the person back into scientific psychology, this time forever. Measurement: Interdisciplinary Research and Perspectives 2(4):201–18.Google Scholar
Monroe, S. M., Harkness, K., Simons, A. D. & Thase, M. E. (2001) Life stress and the symptoms of major depression. Journal of Nervous and Mental Disease 189:168–75.Google Scholar
Neale, M. C. & Kendler, K. S. (1995) Models of comorbidity for multifactorial disorders. American Journal of Human Genetics 57:935–53.Google ScholarPubMed
Newman, M. E. J. (2006) Modularity and community structure in networks. Proceedings of the National Academy of Sciences USA 103:8577–82.CrossRefGoogle ScholarPubMed
Newman, M. E. J. & Girvan, M. (2004) Finding and evaluating community structure in networks. Physical Review E 69:026113.Google Scholar
Nierenberg, A. A., Ostacher, M. J., Huffman, J. C., Ametrano, R. M., Fava, M. & Perlis, R. H. (2008) A brief review of antidepressant efficacy, effectiveness, indications, and usage for major depressive disorder. Journal of Occupational and Environmental Medicine 50:428–36.Google Scholar
Palmer, T. N. (2001) A nonlinear dynamical perspective on model error: A proposal for non-local stochastic-dynamic parametrization in weather and climate prediction models. Quarterly Journal of the Royal Meteorological Society 127:279–304.Google Scholar
Pearl, J. (2000) Causality: Models, reasoning, and inference. Cambridge University Press.Google Scholar
Pisarchik, A. N. & Goswami, B. K. (2000) Annihilation of one of the coexisting attractors in a bistable system. Physical Review Letters 84:1423–26.Google Scholar
Posternak, M. A. & Miller, I. (2001) Untreated short-term course of major depression: A meta-analysis of outcomes from studies using wait-list control groups. Journal of Affective Disorders 66:139–46.CrossRefGoogle ScholarPubMed
Reichardt, J. & Bornholdt, S. (2006) When are networks truly modular? Physical Review E 74:016110. (Online publication).CrossRefGoogle Scholar
Richters, J. E. & Hinshaw, S. P. (1999) The abduction of disorder in psychiatry. Journal of Abnormal Psychology 108:438–45.CrossRefGoogle ScholarPubMed
Roelofs, J., Huibers, M., Peeters, F. & Arntz, A. (2008a) Effects of neuroticism on depression and anxiety: Rumination as possible mediator. Personality and Individual Differences 44:576–86.CrossRefGoogle Scholar
Roelofs, J., Huibers, M., Peeters, F., Arntz, A. & Van Os, J. (2008b) Rumination and worrying as possible mediators in the relation between neuroticism and symptoms of depression and anxiety in clinically depressed individuals. Behaviour Research and Therapy 46:1283–89.Google Scholar
Rothbaum, B. O. & Schwartz, A. C. (2002) Exposure therapy for posttraumatic stress disorder. American Journal of Psychotherapy 56:59–75.Google Scholar
Rubinov, M., Knock, S. A., Stam, C. J., Micheloyannis, S., Harris, A. W. F., Williams, L. M. & Breakspear, M. (2009) Small-world properties of nonlinear brain activity in schizophrenia. Human Brain Mapping 30:403–16.Google Scholar
Schoevers, R. A., Deeg, D. J. H., Van Tilburg, W. & Beekman, A. T. F. (2005) Anxiety and depression: Co-occurrence and longitudinal patterns in elderly patients. American Journal of Geriatric Psychiatry 13:31–39.CrossRefGoogle ScholarPubMed
Seligman, L. D. & Ollendick, T. H. (1998) Comorbidity of anxiety and depression in children and adolescents: An integrative review. Clinical Child and Family Psychology Review 1:125–44.CrossRefGoogle ScholarPubMed
Shannon, P., Markiel, A., Ozier, O., Baliga, N. S., Wang, J. T., Ramage, D., Amin, N., Schwikowski, B. & Ideker, T. (2003) Cytoscape: A software environment for integrated models of biomolecular interaction networks. Genome Research 13:2498–504.CrossRefGoogle ScholarPubMed
Shoda, Y., LeeTiernan, S. & Mischel, W. (2002) Personality as a dynamical system: Emergence of stability and distinctiveness from intra- and interpersonal interactions. Personality and Social Psychology Review 6:316–25.Google Scholar
Solé, R. V., Ferrer-Cancho, R., Montoya, J. M. & Valverde, S. (2000) Selection, tinkering, and emergence in complex networks. Complexity 8:20–33.CrossRefGoogle Scholar
Solomon, A., Haaga, D. A. F. & Arnow, B. A. (2001) Is clinical depression distinct from subthreshold depressive symptoms? A review of the continuity issue in depression research. Journal of Nervous and Mental Disease 189:498–506.Google Scholar
Spitzer, R. L. (1973) A proposal about homosexuality and the APA nomenclature: Homosexuality as an irregular form of sexual behavior and sexual orientation disturbance as a psychiatric disorder. A symposium: Should homosexuality be in the APA nomenclature? American Journal of Psychiatry 130:1207–16.Google Scholar
Spitzer, R. L. (1999) Harmful dysfunction and the DSM definition of mental disorder. Journal of Abnormal Psychology 108:430–32.Google Scholar
Spitzer, R. L. & Endicott, J. (1978) Medical and mental disorder: Proposed definition and criteria. In: Critical issues in psychiatric diagnosis, ed. Klein, D. F. & Spitzer, R. L., pp. 15–40. Raven.Google Scholar
Strogatz, S. H. (2001) Exploring complex networks. Nature 41:268–76.Google Scholar
Van der Maas, H. L. J., Dolan, C. V., Grasman, R. P. P. P., Wicherts, J. M., Huizenga, H. M. & Raijmakers, M. E. J. (2006) A dynamical model of general intelligence: The positive manifold of intelligence by mutualism. Psychological Review 113(4):842–61.Google Scholar
Van Geert, P. (1998) A dynamic systems model of basic developmental mechanisms: Piaget, Vygotsky, and beyond. Psychological Review 105:634–77.CrossRefGoogle Scholar
Wadsworth, M. E., Hudziak, J. J., Heath, A. C. & Achenbach, T. M. (2001) Latent class analysis of Child Behavior Checklist anxiety/depression in children and adolescents. Journal of the American Academy of Child and Adolescent Psychiatry 40:106–14.Google Scholar
Wakefield, J. C. (1992) The concept of mental disorder: On the boundary between biological facts and social values. American Psychologist 47:373–88.Google Scholar
Wakefield, J. C. (1999a) Evolutionary versus prototype analyses of the concept of disorder. Journal of Abnormal Psychology 108:374–99.CrossRefGoogle ScholarPubMed
Wakefield, J. C. (1999b) Mental disorder as a black box essentialist concept. Journal of Abnormal Psychology 108:465–72.CrossRefGoogle Scholar
Wang, X. F. (2002) Complex networks: Topology, dynamics and synchronization. International Journal of Bifurcation and Chaos in Applied Sciences and Engineering 12:885–916.Google Scholar
Watson, D. (2005) Rethinking the mood and anxiety disorders: A quantitative hierarchical model for DSM-V. Journal of Abnormal Psychology 114:522–36.CrossRefGoogle ScholarPubMed
Watson, D., Weber, K., Assenheimer, J. S., Clark, L. A., Strauss, M. E. & McCormick, R. A. (1995) Testing a tripartite model: I. Evaluating the convergent and discriminant validity of anxiety and depression symptom scales. Journal of Abnormal Psychology 104:3–14.CrossRefGoogle ScholarPubMed
Watts, D. J. & Strogatz, S. H. (1998) Collective dynamics of “small-world” networks. Nature 393:440–42.Google Scholar
Zachar, P. (2000) Psychiatric disorders are not natural kinds. Philosophy, Psychiatry and Psychology 7:167–82.Google Scholar
Zachar, P. & Kendler, K. S. (2007) Psychiatric disorders: A conceptual taxonomy. American Journal of Psychiatry 164:557–65.CrossRefGoogle ScholarPubMed