Progress in the Study of Negative Symptoms

Schizophrenia Bulletin vol. 40 suppl. no. 2 pp. S101–S106, 2014 doi:10.1093/schbul/sbt158

Progress in the Study of Negative Symptoms

Brian Kirkpatrick*,1 Department of Psychiatry and Behavioral Sciences, School of Medicine, University of Nevada, Reno

1

*To whom correspondence should be addressed; Department of Psychiatry and Behavioral Sciences, University of Nevada School of Medicine,1664 North Virginia Street, Mail Stop 0354, Reno, NV 89557-0354, US; tel: 775-682-8449, fax: 775-784-1428, e-mail: [email protected]

Key words: festschrift/factor analysis/Carpenter/ negative symptoms/deficit/randomized clinical trials/ nosology Negative symptoms account for a substantial part of the impairment suffered by people with schizophrenia1 and have long been a focus of research on schizophrenia. Recognizable descriptions of the negative symptoms of schizophrenia can be found as early as the mid-1800s, with Wilhelm Griesinger’s descriptions of an “absence of will,”2 followed by Kraepelin’s description of a “weakening of ….the mainsprings of volition” among some people with schizophrenia.3 A landmark development in the scientific study of negative symptoms was the publication of the Brief Psychiatric Rating Scale in 1962,4 which has been cited more than 7500 times in the world literature and included negative symptom items. The Scale for the Assessment of Negative Symptoms5 brought further attention to negative symptoms as a separate area of research and, potentially, a separate therapeutic target and greatly facilitated progress in the study of negative symptoms. The present review of recent developments in the concept of negative symptoms grew out of a presentation at the festschrift for William T. Carpenter Jr, held in June 2013. It reviews areas of research on negative symptoms in which he has made important contributions: the nosology of negative symptoms; the distinction between primary vs secondary symptoms; and the appropriate design for negative symptom treatment trials.

Nosology In 1974, Carpenter and coworkers proposed separating, for research purposes, 3 groups of symptoms within schizophrenia: positive symptoms, negative symptoms, and problems in interpersonal relationships.6 On the basis of the many factor analytic studies of the psychopathology of schizophrenia that appeared after that proposal, Buchanan and Carpenter subsequently outlined a research strategy that distinguished among positive symptoms, negative symptoms, and disorganization.7 In this approach, one would, by testing many individual hypotheses, test the overarching hypothesis that these domains have distinctive risk factors, course, treatment response, and biological correlates. This “domains of psychopathology” strategy led to a proposal for a default analysis of studies of schizophrenia.8 In 2005 Carpenter cochaired the Consensus Development Conference on Negative Symptoms sponsored by the US National Institute of Mental Health. The Conference resulted in a recommendation that a new instrument for quantifying negative symptoms be developed. Two instruments grew out of that recommendation: the Brief Negative Symptom Scale (BNSS)9,10 and the Clinical Assessment Interview for Negative Symptoms (CAINS)11,12. At the Consensus Development Conference, a review of the factor analytic studies of the Scale for the Assessment of Negative Symptoms was presented. In those studies, 2 factors were found with some consistency (sometimes, additional factors were found as well)13: an expressivity factor consisting of blunted affect and alogia, and a factor that combines anhedonia, avolition, and asociality. Subsequently, very similar factors were found using the BNSS, the Schedule for the Deficit Syndrome,14 and the CAINS9,11,12,14,15. Of the 2 new scales that implement the recommendations of the Consensus Development Conference—the BNSS and CAINS—the BNSS has so far had somewhat stronger item loading for a crisper separation of the 2 factors.9,11,12,15–18 One study found good stability of these factors at 5-year follow-up.16 The negative

© The Author 2014. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved. For permissions, please email: [email protected]

S101

Downloaded from http://schizophreniabulletin.oxfordjournals.org/ by guest on December 30, 2015

A selective review of the negative symptoms of schizophrenia is an appropriate article to result from the festschrift honoring William T. Carpenter Jr, as he has made substantial contributions in this area. This review assesses progress in 3 areas in which he has been an important investigator: the distinction between primary vs secondary negative symptoms; the appropriate design for treatment trials; and the nosology of negative symptoms.

B. Kirkpatrick

symptom items on the Positive and Negative Syndrome Scale does not appear to yield these 2 factors consistently.19 The significance of these factors is not yet clear; to date, there are relatively few studies of their correlates. However, the avolition factor may be a stronger prediction of overall function than is the expressivity factor,16,20 and the 2 factors may differ in their response to certain treatments.21 In principle, rapid progress on understanding the significance of these 2 factors should be possible, because an analysis of the correlates of expressivity vs avolition/anhedonia is possible in most studies of negative symptoms. Primary vs Secondary Symptoms

Signs and Symptoms There are symptomatic differences between the 2 groups in addition to those used to make the diagnosis. Deficit patients have less awareness of their impairments, including dyskinetic movements,27,28 as well as less anxiety and depression. The anxiety and depression differences are S102

Course of Illness Deficit patients have, on average, greater social dysfunction prior to the onset of psychosis than do nondeficit patients.33 In contrast to what one might expect in a group with poorer social function, deficit patients have on average less severe drug abuse.34 Deficit patients also have poorer outcome on follow-up, as shown in 2 separate studies (1 from Italy) with 5 years of follow-up, and 1 with an average follow-up of 19 years.1,16,24 Despite their poorer function but consistent with their less severe depression and poorer insight, deficit patients less frequently have suicidal thoughts and may have less risk of suicide.24 Etiological and Risk Factors An association between deficit schizophrenia and summer birth has been found in studies from 6 countries35 but may not exist in lower latitudes.36 The combination of a replicated summer birth association for deficit schizophrenia, and an association with winter for schizophrenia as a whole—ie, both deficit and nondeficit groups—suggests that winter birth is a risk factor for nondeficit schizophrenia alone. Compared with nondeficit probands, patients with deficit schizophrenia have a higher prevalence of psychosis among their relatives.37,38 The nonpsychotic relatives of deficit probands also have a greater prevalence of deficit-like features than do the relatives of nondeficit probands,38 and within schizophrenia, there is a significant sibling concordance for the deficit/nondeficit categorization.39 Antibodies to cytomegalovirus but not other herpes viruses were found to be more prevalent in people with deficit compared with nondeficit schizophrenia.40 Biological Correlates The deficit and nondeficit groups differ on several biological correlates. Imaging. Deficit/nondeficit differences have been found in studies of structural, functional, and neurochemical imaging. Arango et al41 found that male deficit patients had significantly larger ventricles than nonpatient control subjects, but there was no difference between control subjects


In 1988, Carpenter and coworkers22 argued that it is important to distinguish negative symptoms that are secondary to factors such as depression, a suspicious withdrawal, overwhelming psychotic symptoms, and extrapyramidal side effects from those symptoms that cannot be attributed to such factors. They termed symptoms that could not be attributed to these other factors—and therefore are due to the disease itself—primary symptoms, in contrast to symptoms secondary to these factors. They argued that people with schizophrenia who have enduring, primary symptoms were more likely to comprise a meaningful subtype than a negative symptom subtype that included patients with both primary and secondary symptoms. Carpenter et al22 proposed diagnostic criteria to distinguish deficit patients—those with primary, enduring negative symptoms—from nondeficit patients, who do not have such symptoms. The Maryland group subsequently published a refined version of the diagnostic criteria as well as a manual for making this distinction.14 The same group of investigators later used the term deficit schizophrenia to refer to schizophrenia with primary, enduring negative symptoms, in contrast to nondeficit schizophrenia, in which any negative symptoms are considered secondary.23 The Maryland group demonstrated strong reliability for this categorization,14 but there remained a question whether other researchers could also do so. Reports of good interrater agreement in other research groups soon followed, as did evidence of the stability of the diagnosis.24,25 The present brief review of the validity of the deficit/ nondeficit categorization is organized into 5 dimensions that distinguish diseases: signs and symptoms, course of illness, etiological and risk factors, biological correlates, and treatment response. More detailed reviews of deficit/ nondeficit differences have been published.23,26

stable,1,29 and the lesser severity of these symptoms in the deficit group contrasts with their poorer social function and greater social isolation.24 The 2 groups do not differ on psychotic symptoms: hallucinations, delusions, and disorganized thought and behavior. However, deficit patients’ lack of social drive extends to the content of their delusions, because they have less severe delusions with an exclusively social content.30 Deficit patients also have a greater risk of dyskinetic movements than do nondeficit patients, a difference that is not confounded by differences in treatment history.31,32

Negative Symptoms

Metabolic Differences. In a study of newly diagnosed, antipsychotic-naive patients, both deficit and nondeficit subjects had abnormal glucose tolerance compared with matched controls subjects. However, the deficit patients had significantly less severe glucose intolerance than did nondeficit patients. In contrast, although deficit patients had abnormally high interleukin-6 concentrations compared with control subjects, nondeficit patients did not differ from control subjects and had significantly lower concentrations than deficit patients.49,50 Neurocognitive Measures. In a meta-analysis, deficit patients were found to have greater cognitive impairment than nondeficit patients, with a pattern that was not consistent with a discrete anatomical distribution.51 In a study in which deficit patients had significantly poorer

performance on the continuous performance test (CPT) and span of apprehension tasks than nondeficit patients, the nondeficit group did not differ from control subjects on the CPT, but were significantly impaired compared with control subjects on the span of apprehension task.52 Mucci and coworkers53 found a double dissociation in event-related potentials. Deficit but not nondeficit patients differed from control subjects on N1 amplitude and current source density, while nondeficit but not deficit patients differed from control subjects on P3 measures. The 2 patient groups also differed from each other on these measures. In contrast, deficit and nondeficit groups were found not to differ on P50 gating with an auditory stimulus.54 Deficit patients have a significantly greater impairment in smell identification than nondeficit patients; this relationship is correlated with a measure of their asociality but is not due to differences in intelligence quotient.55–57 Deficit patients also rate pleasant smells as less pleasant than do nondeficit patients.58 In a study of neurological signs, deficit patients had greater impairment than nondeficit paitnets in sensory integration, but the groups did not differ on other groups of neurological signs, or on total neurological impairment.59 Treatment Response There is no evidence that there is a difference between deficit and nondeficit patients in terms of the response of their positive psychotic symptoms to antipsychotics. However, preliminary studies of both psychosocial and pharmacological treatments suggest that some treatment that are effective for the negative symptoms of nondeficit patients are less effective, or ineffective, among deficit patients.60,61 Summary This review of deficit/nondeficit differences suggests that the deficit group constitutes a separate disease within the syndrome of schizophrenia. These differences are not confounded by deficit/nondeficit differences in demographic features, antipsychotic treatment, or the severity of psychotic symptoms or drug abuse. Some correlates of primary, enduring negative symptoms differ from those of negative symptoms more broadly defined.1,37 Several findings refute the interpretation that the deficit group simply has a more severe form of the same etiopathophysiology as nondeficit schizophrenia, including the deficit group’s decreased drug abuse, less severe depression and parasuicidal behavior, summer rather than winter birth, and double dissociations in metabolic and event-related potential measures. Imaging studies and the meta-analysis of neuropsychological studies, taken together, are consistent with the view that people with deficit schizophrenia have a pathophysiological process that affects many areas in the brain. This S103


and either male nondeficit patients or female patients. Fischer et al42 found smaller gray matter volumes in deficit patients, compared with both nondeficit patients and control subjects, in the superior prefrontal, superior temporal, and middle temporal gyri. There was no difference in any of several subcortical areas. Voineskos and coworkers43 found a difference between deficit and nondeficit groups in white matter integrity as measured by diffusion tensor imaging. The difference was widespread; there were some suggestions that the difference was particularly large in the right arcuate, left uncinate, and right inferior longitudinal fasciculi. These bundles extend to many anatomical areas. In the same study, there was no difference in cortical thickness, but the deficit sample was relatively small. Tamminga et al44 found decreased activation in deficit compared with both nondeficit patients and control subjects in the thalamus, as well as in frontal and parietal cortex. Other functional differences have also been found: increased activation in the left amygdala of deficit patients in response to an emotional facial recognition task, which the investigators interpreted as due to an abnormality in habituation45; and, using memory tasks, less activation in the frontal cortex in deficit compared with nondeficit patients.46 A neurochemical imaging study of deficit and nondeficit patients found a lower N-acetylaspartate/creatine (NAC) ratio in the prefrontal cortex of deficit patients compared with nondeficit patients and control subjects, a difference the investigators suggested reflected a loss of neurons in the prefrontal cortex of deficit patients.47 The same group subsequently found NAC levels were correlated with Stroop scores in deficit but not nondeficit patients or control subjects, suggesting a relationship between poor right medial prefrontal cortex function and poor selective attention exists only in deficit patients.48 Taken together, the imaging studies suggest deficit/ nondeficit differences are widespread, and the differences do not appear to be present solely in either gray or white matter.

B. Kirkpatrick

Treatment Trials of Negative Symptoms Demonstration of the validity of the primary/secondary distinction provided a basis for a proposed study design for treatment trials focused on negative symptoms.64,65 In this approach, only patients with stable and moderate to severe negative symptoms, but with minimal positive symptoms and depression, would be enrolled in such a trial. This design provides a method for dealing with the problem that arises in interpreting treatment studies: if both negative symptoms and positive psychotic symptoms improve, the negative symptom improvement may be due to an improvement in secondary negative symptoms only. This design has subsequently been adopted by academic and industry investigators,21,66,67 and it was endorsed by the Consensus Development Conference cochaired by Dr Carpenter. Discussion Negative symptoms constitute one of the most impairing aspects of schizophrenia, and to date, treatments for these problems have been very disappointing. Recent treatment studies22,67 and greater understanding of the biological underpinnings of negative symptoms raise the hope that this situation will change. Through his work, William T. Carpenter Jr has contributed greatly to this progress. Acknowledgment The author has declared that there are no conflicts of interest in relation to the subject of this study. References 1. Tek C, Kirkpatrick B, Buchanan RW. A five-year followup study of deficit and nondeficit schizophrenia. Schizophr Res. 2001;49:253–260. 2. Griesinger W. Mental Pathology and Therapeutics. 2nd ed. Robertson CL, Rutherford J, trans. London: New Sydenham Society; 1867.

S104

3. Kraepelin E. Dementia Praecox and Paraphrenia. Melbourne, FL: Krieger (originally published in 1919); 1971. 4. Overall JE, Gorham DR. The Brief Psychiatric Rating Scale. Psycholog Rep. 1962;10:799–812. 5. Andreasen NC. Negative symptoms in schizophrenia. Definition and reliability. Arch Gen Psychiatry. 1982;39:784–788. 6. Strauss JS, Carpenter WT Jr, Bartko JJ. The diagnosis and understanding of schizophrenia. Part III. Speculations on the processes that underlie schizophrenic symptoms and signs. Schizophr Bull. 1974;11:61–69. 7. Buchanan RW, Carpenter WT. Domains of psychopathology: an approach to the reduction of heterogeneity in schizophrenia. J Nerv Ment Dis. 1994;182:193–204. 8. Kirkpatrick B, Ryan WG. A default analysis for schizophrenia research. Schizophr Bull. 2000;26:157–162. 9. Kirkpatrick B, Strauss GP, Nguyen L, et al. The brief negative symptom scale: psychometric properties. Schizophr Bull. 2011;37:300–305. 10. Strauss GP, Keller WR, Buchanan RW, et al. Next-generation negative symptom assessment for clinical trials: validation of the Brief Negative Symptom Scale. Schizophr Res. 2012;142:88–92. 11. Horan WP, Kring AM, Gur RE, Reise SP, Blanchard JJ. Development and psychometric validation of the Clinical Assessment Interview for Negative Symptoms (CAINS). Schizophr Res. 2011;132:140–145. 12. Kring AM, Gur RE, Blanchard JJ, Horan WP, Reise SP. The Clinical Assessment Interview for Negative Symptoms (CAINS): final development and validation. Am J Psychiatry. 2013;170:165–172. 13. Blanchard JJ, Cohen AS. The structure of negative symptoms within schizophrenia: implications for assessment. Schizophr Bull. 2006;32:238–245. 14. Kirkpatrick B, Buchanan RW, McKenney PD, Alphs LD, Carpenter WT Jr. The Schedule for the Deficit syndrome: an instrument for research in schizophrenia. Psychiatry Res. 1989;30:119–123. 15. Strauss GP, Hong LE, Gold JM, et al. Factor structure of the Brief Negative Symptom Scale. Schizophr Res. 2012;142:96–98. 16. Galderisi S, Bucci P, Mucci A, et al. Categorical and dimensional approaches to negative symptoms of schizophrenia: focus on long-term stability and functional outcome. Schizophr Res. 2013;147:157–162. 17. Nakaya M, Ohmori K. A two-factor structure for the Schedule for the Deficit Syndrome in schizophrenia. Psychiatry Res. 2008;158:256–259. 18. Kimhy D, Yale S, Goetz RR, McFarr LM, Malaspina D. The factorial structure of the schedule for the deficit syndrome in schizophrenia. Schizophr Bull. 2006;32:274–278. 19. Liemburg E, Castelein S, Stewart R, van der Gaag M, Aleman A, Knegtering H; Genetic Risk and Outcome of Psychosis (GROUP) Investigators. Two subdomains of negative symptoms in psychotic disorders: established and confirmed in two large cohorts. J Psychiatr Res. 2013;47:718–725. 20. Strauss GP, Horan WP, Kirkpatrick B, et al. Deconstructing negative symptoms of schizophrenia: avolition-apathy and diminished expression clusters predict clinical presentation and functional outcome. J Psychiatr Res. 2013;47:783–790. 21. Umbricht D, Lentz E, Lalonde J, Martin-Facklam M, Santarelli L. The effect of bitopertin, a glycine reuptake


view is consistent with the increased density of interstitial cells of the white matter in deficit subjects, compared with nondeficit schizophrenia subjects and nonpatient control subjects, that has been found in both the dorsolateral prefrontal cortex and inferior parietal cortex.62,63 The abnormality in this cell population further suggests that there is a deficit/nondeficit difference in neuronal migration during gestation and that this difference is the basis of the clinical differences. It is intriguing to speculate that this abnormal migration in the deficit group is related to one or more of the risk factors associated with deficit but not nondeficit schizophrenia. However, while the summer birth effect and a different familial risk have been replicated, the cytomegalovirus difference—which might lend itself to animal studies—has not.

Negative Symptoms

40. Dickerson F, Kirkpatrick B, Boronow J, Stallings C, Origoni A, Yolken R. Deficit schizophrenia: association with serum antibodies to cytomegalovirus. Schizophr Bull. 2006;32:396–400. 41. Arango C, McMahon RP, Lefkowitz DM, Pearlson G, Kirkpatrick B, Buchanan RW. Patterns of cranial, brain and sulcal CSF volumes in male and female deficit and nondeficit patients with schizophrenia. Psychiatry Res. 2008;162:91–100. 42. Fischer BA, Keller WR, Arango C, et al. Cortical structural abnormalities in deficit versus nondeficit schizophrenia. Schizophr Res. 2012;136:51–54. 43. Voineskos AN, Foussias G, Lerch J, et al. Neuroimaging evidence for the deficit subtype of schizophrenia. JAMA Psychiatry. 2013;70:472–480. 44. Tamminga CA, Thaker GK, Buchanan R, et al. Limbic system abnormalities identified in schizophrenia using positron emission tomography with fluorodeoxyglucose and neocortical alterations with deficit syndrome. Arch Gen Psychiatry. 1992;49:522–530. 45. Fernandez-Egea E, Parelada E, Sugranyes G, et al. Left amygdalar activation in deficit syndrome compared with nondeficit subjects with schizophrenia during the control task in a facial emotion recognition paradigm. Psychiatry Res. 2012;203:109–110. 46. Heckers S, Goff D, Schacter DL, et al. Functional imaging of memory retrieval in deficit vs nondeficit schizophrenia. Arch Gen Psychiatry. 1999;56:1117–1123. 47. Delamillieure P, Fernandez J, Constans JM, et al. Proton magnetic resonance spectroscopy of the medial prefrontal cortex in patients with deficit schizophrenia: preliminary report. Am J Psychiatry. 2000;157:641–643. 48. Delamillieure P, Constans JM, Fernandez J, Brazo P, Dollfus S. Relationship between performance on the Stroop test and N-acetylaspartate in the medial prefrontal cortex in deficit and nondeficit schizophrenia: preliminary results. Psychiatry Res. 2004;132:87–89. 49. Kirkpatrick B, Fernandez-Egea E, Garcia-Rizo C, Bernardo M. Differences in glucose tolerance between deficit and nondeficit schizophrenia. Schizophr Res. 2009;107:122–127. 50. Garcia-Rizo C, Fernandez-Egea E, Oliveira C, Justicia A, Bernardo M, Kirkpatrick B. Inflammatory markers in antipsychotic-naïve patients with nonaffective psychosis and deficit vs. nondeficit features. Schizophr Res. 2012;134:16–19. 51. Cohen AS, Saperstein AM, Gold JM, Kirkpatrick B, Carpenter WT Jr, Buchanan RW. Neuropsychology of the deficit syndrome: new data and meta-analysis of findings to date. Schizophr Bull. 2007;33:1201–1212. 52. Buchanan RW, Strauss ME, Breier A, Kirkpatrick B, Carpenter WT Jr. Attentional impairments in deficit and nondeficit forms of schizophrenia. Am J Psychiatry. 1997;154:363–370. 53. Mucci A, Galderisi S, Kirkpatrick B, et al. Double dissociation of N1 and P3 abnormalities in deficit and nondeficit schizophrenia. Schizophr Res. 2007;92:252–261. 54. Santos JL, Sánchez-Morla EM, Aparicio A, et al. P50 gating in deficit and nondeficit schizophrenia. Schizophr Res. 2010;119:183–190. 55. Seckinger RA, Goudsmit N, Coleman E, et al. Olfactory identification and WAIS-R performance in deficit and nondeficit schizophrenia. Schizophr Res. 2004;69:55–65.

S105


inhibitor, on key negative symptom dimensions and association with estimated GlyT1 occupancy [abstracts]. International Congress on Schizophrenia Research, 2013. 22. Carpenter WT Jr, Heinrichs DW, Wagman AM. Deficit and nondeficit forms of schizophrenia: the concept. Am J Psychiatry. 1988;145:578–583. 23. Kirkpatrick B, Buchanan RW, Ross DE, Carpenter WT Jr. A separate disease within the syndrome of schizophrenia. Arch Gen Psychiatry. 2001;58:165–171. 24. Fenton WS, McGlashan TH. Antecedents, symptom progression, and long-term outcome of the deficit syndrome in schizophrenia. Am J Psychiatry. 1994;151:351–356. 25. Amador XF, Kirkpatrick B, Buchanan RW, Carpenter WT, Marcinko L, Yale SA. Stability of the diagnosis of deficit syndrome in schizophrenia. Am J Psychiatry. 1999;156:637–639. 26. Kirkpatrick B, Galderisi S. Deficit schizophrenia: an update. World Psychiatry. 2008;7:143–147. 27. Arango C, Adami H, Sherr JD, Thaker GK, Carpenter WT Jr. Relationship of awareness of dyskinesia in schizophrenia to insight into mental illness. Am J Psychiatry. 1999;156:1097–1099. 28. Trotman HD, Kirkpatrick B, Compton MT. Impaired insight in patients with newly diagnosed nonaffective psychotic disorders with and without deficit features. Schizophr Res. 2011;126:252–256. 29. Kirkpatrick B, Buchanan RW, Breier A, Carpenter WT Jr. Case identification and stability of the deficit syndrome of schizophrenia. Psychiatry Res. 1993;47:47–56. 30. Kirkpatrick B, Amador XF, Yale SA, Bustillo JR, Buchanan RW, Tohen M. The deficit syndrome in the DSM-IV Field Trial. Part II. Depressive episodes and persecutory beliefs. Schizophr Res. 1996;20:79–90. 31. Fenton WS, Wyatt RJ, McGlashan TH. Risk factors for spontaneous dyskinesia in schizophrenia. Arch Gen Psychiatry. 1994;51:643–650. 32. Telfer S, Shivashankar S, Krishnadas R, McCreadie RG, Kirkpatrick B. Tardive dyskinesia and deficit schizophrenia. Acta Psychiatr Scand. 2011;124:357–362. 33. Buchanan RW, Kirkpatrick B, Heinrichs DW, Carpenter WT Jr. Clinical correlates of the deficit syndrome of schizophrenia. Am J Psychiatry. 1990;147:290–294. 34. Kirkpatrick B, Amador XF, Yale SA, Bustillo JR, Buchanan RW, Tohen M. The deficit syndrome in the DSM-IV Field Trial. Part II. Depressive episodes and persecutory beliefs. Schizophr Res. 1996;20:79–90. 35. Messias E, Kirkpatrick B, Bromet E, et al. Summer birth and deficit schizophrenia: a pooled analysis from 6 countries. Arch Gen Psychiatry. 2004;61:985–989. 36. Welham J, Chant D, Saha S, McGrath J, Kirkpatrick B, Castle D. No association between the deficit syndrome in psychosis and summer birth in a Southern hemisphere country. Aust N Z J Psychiatry. 2006;40:935–936. 37. Kirkpatrick B, Castle D, Murray RM, Carpenter WT Jr. Risk factors for the deficit syndrome of schizophrenia. Schizophr Bull. 2000;26:233–242. 38. Kirkpatrick B, Ross DE, Walsh D, Karkowski L, Kendler KS. Family characteristics of deficit and nondeficit schizophrenia in the Roscommon Family Study. Schizophr Res. 2000;45:57–64. 39. Ross DE, Kirkpatrick B, Karkowski LM, et al. Sibling correlation of deficit syndrome in the Irish study of high-density schizophrenia families. Am J Psychiatry. 2000;157:1071–1076.

B. Kirkpatrick

S106

parietal cortex in schizophrenia: An unbiased cell-counting study. Synapse. 1999;34:95–102. 63. Kirkpatrick B, Messias NC, Conley RR, Roberts RC. Interstitial cells of the white matter in the dorsolateral prefrontal cortex in deficit and nondeficit schizophrenia. J Nerv Ment Dis. 2003;191:563–567. 64. Kirkpatrick B, Kopelowicz A, Buchanan RW, Carpenter WT Jr. Assessing the efficacy of treatments for the deficit syndrome of schizophrenia. Neuropsychopharmacology. 2000;22:303–310. 65. Kirkpatrick B, Fenton WS, Carpenter WT Jr, Marder SR. The NIMH-MATRICS consensus statement on negative symptoms. Schizophr Bull. 2006;32:214–219. 66. Buchanan RW, Javitt DC, Marder SR, et al. The Cognitive and Negative Symptoms in Schizophrenia Trial (CONSIST): the efficacy of glutamatergic agents for negative symptoms and cognitive impairments. Am J Psychiatry. 2007;164:1593–1602. 67. Freedman R, Olincy A, Buchanan RW, et al. Initial phase 2 trial of a nicotinic agonist in schizophrenia. Am J Psychiatry. 2008;165:1040–1047.


56. Goudsmit N, Coleman E, Seckinger RA, et al. A brief smell identification test discriminates between deficit and non-deficit schizophrenia. Psychiatry Res. 2003;120:155–164. 57. Malaspina D, Coleman E, Goetz RR, et al. Odor identification, eye tracking and deficit syndrome schizophrenia. Biol Psychiatry. 2002;51:809–815. 58. Strauss GP, Allen DN, Ross SA, Duke LA, Schwartz J. Olfactory hedonic judgment in patients with deficit syndrome schizophrenia. Schizophr Bull. 2010;36:860–868. 59. Arango C, Kirkpatrick B, Buchanan RW. Neurological signs and the heterogeneity of schizophrenia. Am J Psychiatry. 2000;157:560–565. 60. Kopelowicz A, Liberman RP, Mintz J, Zarate R. Comparison of efficacy of social skills training for deficit and nondeficit negative symptoms in schizophrenia. Am J Psychiatry. 1997;154:424–425. 61. Kopelowicz A, Zarate R, Tripodis K, Gonzalez V, Mintz J. Differential efficacy of olanzapine for deficit and nondeficit negative symptoms in schizophrenia. Am J Psychiatry. 2000;157:987–993. 62. Kirkpatrick B, Conley RC, Kakoyannis A, Reep RL, Roberts RC. Interstitial cells of the white matter in the inferior