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Meta-analyses of cognitive functioning in euthymic bipolar patients and their first-degree relatives

Published online by Cambridge University Press:  09 October 2007

B. Arts ,
N. Jabben ,
L. Krabbendam  and
J. van Os
B. Arts*
Affiliation:
Department of Psychiatry and Neuropsychology, South Limburg Mental Health Research and Teaching Network, EURON, Maastricht University, PO Box 616 (KAP2), 6200 MDMaastricht, The Netherlands
N. Jabben
Affiliation:
Department of Psychiatry and Neuropsychology, South Limburg Mental Health Research and Teaching Network, EURON, Maastricht University, PO Box 616 (KAP2), 6200 MDMaastricht, The Netherlands
L. Krabbendam
Affiliation:
Department of Psychiatry and Neuropsychology, South Limburg Mental Health Research and Teaching Network, EURON, Maastricht University, PO Box 616 (KAP2), 6200 MDMaastricht, The Netherlands
J. van Os
Affiliation:
Department of Psychiatry and Neuropsychology, South Limburg Mental Health Research and Teaching Network, EURON, Maastricht University, PO Box 616 (KAP2), 6200 MDMaastricht, The Netherlands Division of Psychological Medicine, Institute of Psychiatry, London, UK
*
*Address for correspondence: B. M. G. Arts, Department of Psychiatry and Neuropsychology, South Limburg Mental Health Research and Teaching Network, EURON, Maastricht University, PO Box 616 (KAP2), 6200 MDMaastricht, The Netherlands. (Email: b.arts@np.unimaas.nl)
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Abstract

Background

Previous work suggests that impairments in executive function and verbal memory in particular may persist in euthymic bipolar patients and serve as an indicator of genetic risk (endophenotype).

Method

A systematic review of the literature was undertaken. Effects sizes were extracted from selected papers and pooled using meta-analytical techniques.

Results

In bipolar patients, large effect sizes (d>0.8) were noted for executive functions (working memory, executive control, fluency) and verbal memory. Medium effect sizes (0.5<d<0.8) were reported for aspects of executive function (concept shifting, executive control), mental speed, visual memory, and sustained attention. Small effect sizes (d<0.5) were found for visuoperception. In first-degree relatives, effect sizes were small (d<0.5), but significantly different from healthy controls for executive function and verbal memory in particular.

Conclusions

Executive function and verbal memory are candidate bipolar endophenotypes given large deficits in these domains in bipolar patients and small, but intermediate, cognitive impairments in first-degree relatives.

Keywords

Bipolar patientscognitionmeta-analysisrelatives
Type
Review Article
Information
Psychological Medicine , Volume 38 , Issue 6 , June 2008 , pp. 771 - 785
Copyright
Copyright © Cambridge University Press 2007

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References

Altshuler, LL, Ventura, J, van Gorp, WG, Green, MF, Theberge, DC, Mintz, J (2004). Neurocognitive function in clinically stable men with bipolar I disorder or schizophrenia and normal control subjects. Biological Psychiatry 56, 560–569.Google Scholar
Balanza-Martinez, V, Tabares-Seisdebos, R, Selva-Vera, G, Martinez-Aran, A, Torrent, C, Salazar-Fraile, J, Leal-Cerbos, C, Vieta, E, Gomez-Beneyto, M (2005). Persistent cognitive dysfunctions in bipolar I disorder and schizophrenic patients: a 3-year follow-up study. Psychotherapy and Psychosomatics 74, 113–119.Google Scholar
Bath, KG, Lee, FS (2006). Variant BDNF (Val66Met) impact on brain structure and function. Cognitive, Affective and Behavioral Neuroscience 6, 79–85.Google Scholar
Benton, AL, Hamsher, K (1978). Multilingual Aphasia Examination Manual, revised. University of Iowa: Iowa.Google Scholar
Bertolino, A, Caforio, G, Petruzzella, V, Latorre, V, Rubino, V, Dimalta, S, Torraco, A, Blasi, G, Quartesan, R, Mattay, VS, Callicott, JH, Weinberger, DR, Scarabino, T (2006). Prefrontal dysfunction in schizophrenia controlling for COMT Val158Met genotype and working memory performance. Psychiatry Research 147, 221–226.Google Scholar
Bilder, RM, Volavka, J, Lachman, HM, Grace, AA (2004). The catechol-O-methyltransferase polymorphism: relations to the tonic-phasic dopamine hypothesis and neuropsychiatric phenotypes. Neuropsychopharmacology 29, 1943–1961.Google Scholar
Blumberg, HP, Leung, HC, Skudlarski, P, Lacadie, CM, Fredericks, CA, Harris, BC, Charney, DS, Gore, JC, Krystal, JH, Peterson, BS (2003). A functional magnetic resonance imaging study of bipolar disorder: state- and trait-related dysfunction in ventral prefrontal cortices. Archives of General Psychiatry 60, 601–609.Google Scholar
Bozikas, VP, Andreou, C, Giannakou, M, Tonia, T, Anezoulaki, D, Karavatos, A, Fokas, K, Kosmidis, MH (2005). Deficits in sustained attention in schizophrenia but not in bipolar disorder. Schizophrenia Research 78, 225–233.Google Scholar
Brand, N, Jolles, J (1985). Learning and retrieval rate of words presented auditorily and visually. Journal of General Psychology 112, 201–210.Google Scholar
Brooks, JO 3rd, Wang, PW, Strong, C, Sachs, N, Hoblyn, JC, Fenn, R, Ketter, TA (2006). Preliminary evidence of differential relations between prefrontal cortex metabolism and sustained attention in depressed adults with bipolar disorder and healthy controls. Bipolar Disorders 8, 248–254.Google Scholar
Burdick, KE, Goldberg, JF, Harrow, M, Faull, RN, Malhotra, AK (2006). Neurocognition as a stable endophenotype in bipolar disorder and schizophrenia. Journal of Nervous and Mental Disease 194, 255–260.Google Scholar
Cannon, TD, Hennah, W, van Erp, TG, Thompson, PM, Lonnqvist, J, Huttunen, M, Gasperoni, T, Tuulio-Henriksson, A, Pirkola, T, Toga, AW, Kaprio, J, Mazziotta, J, Peltonen, L (2005). Association of DISC1/TRAX haplotypes with schizophrenia, reduced prefrontal gray matter, and impaired short- and long-term memory. Archives of General Psychiatry 62, 1205–1213.Google Scholar
Cavanagh, JT, Van Beck, M, Muir, W, Blackwood, DH (2002). Case-control study of neurocognitive function in euthymic patients with bipolar disorder: an association with mania. British Journal of Psychiatry 180, 320–326.Google Scholar
Christensen, MV, Kyvik, KO, Kessing, LV (2006). Cognitive function in unaffected twins discordant for affective disorder. Psychological Medicine 36, 1119–1129.Google Scholar
Clark, L, Iversen, SD, Goodwin, GM (2002). Sustained attention deficit in bipolar disorder. British Journal of Psychiatry 180, 313–319.Google Scholar
Clark, L, Kempton, MJ, Scarna, A, Grasby, PM, Goodwin, GM (2005 a). Sustained attention-deficit confirmed in euthymic bipolar disorder but not in first-degree relatives of bipolar patients or euthymic unipolar depression. Biological Psychiatry 57, 183–187.Google Scholar
Clark, L, Sarna, A, Goodwin, GM (2005 b). Impairment of executive function but not memory in first-degree relatives of patients with bipolar I disorder and in euthymic patients with unipolar depression. American Journal of Psychiatry 162, 1980–1982.Google Scholar
Craddock, N, O'Donovan, MC, Owen, MJ (2006). Genes for schizophrenia and bipolar disorder? Implications for psychiatric nosology. Schizophrenia Bulletin 32, 9–16.Google Scholar
Deckersbach, T, McMurrich, S, Ogutha, J, Savage, CR, Sachs, G, Rauch, SL (2004 a). Characteristics of non-verbal memory impairment in bipolar disorder: the role of encoding strategies. Psychological Medicine 34, 823–832.Google Scholar
Deckersbach, T, Savage, CR, Reilly-Harrington, N, Clark, L, Sachs, G, Rauch, SL (2004 b). Episodic memory impairment in bipolar disorder and obsessive-compulsive disorder: the role of memory strategies. Bipolar Disorders 6, 233–244.Google Scholar
Delis, DC, Kramer, JH, Kaplan, E, Ober, BA (1987). California Verbal Learning Test: Adult version. The Psychological Corporation: San Antonio, TX.Google Scholar
Dixon, T, Kravariti, E, Frith, C, Murray, RM, McGuire, PK (2004). Effect of symptoms on executive function in bipolar illness. Psychological Medicine 34, 811–821.Google Scholar
Drabant, EM, Hariri, AR, Meyer-Lindenberg, A, Munoz, KE, Mattay, VS, Kolachana, BS, Egan, MF, Weinberger, DR (2006). Catechol O-methyltransferase Val158Met genotype and neural mechanisms related to affective arousal and regulation. Archives of General Psychiatry 63, 1396–1406.Google Scholar
Duff, K, Schoenberg, MR, Scott, JG, Adams, RL (2005). The relationship between executive functioning and verbal and visual learning and memory. Archives of Clinical Neuropsychology 20, 111–122.Google Scholar
Ferrier, IN, Chowdhury, R, Thompson, JM, Watson, S, Young, AH (2004). Neurocognitive function in unaffected first-degree relatives of patients with bipolar disorder: a preliminary report. Bipolar Disorders 6, 319–322.Google Scholar
Ferrier, IN, Stanton, BR, Kelly, TP, Scott, J (1999). Neuropsychological function in euthymic patients with bipolar disorder. British Journal of Psychiatry 175, 246–251.Google Scholar
Fleck, DE, Shear, PK, Zimmerman, ME, Getz, GE, Corey, KB, Jak, A, Lebowitz, BK, Strakowski, SM (2003). Verbal memory in mania: effects of clinical state and task requirements. Bipolar Disorders 5, 375–380.Google Scholar
Frangou, S, Donaldson, S, Hadjulis, M, Landau, S, Goldstein, LH (2005 a). The Maudsley Bipolar Disorder Project: executive dysfunction in bipolar disorder I and its clinical correlates. Biological Psychiatry 58, 859–864.Google Scholar
Frangou, S, Haldane, M, Roddy, D, Kumari, V (2005 b). Evidence for deficit in tasks of ventral, but not dorsal, prefrontal executive function as an endophenotypic marker for bipolar disorder. Biological Psychiatry 58, 838–839.Google Scholar
Glahn, DC, Bearden, CE, Bowden, CL, Soares, JC (2006). Reduced educational attainment in bipolar disorder. Journal of Affective Disorders 92, 309–312.Google Scholar
Glahn, DC, Bearden, CE, Niendam, TA, Escamilla, MA (2004). The feasibility of neuropsychological endophenotypes in the search for genes associated with bipolar affective disorder. Bipolar Disorders 6, 171–182.Google Scholar
Goldberg, TE, Egan, MF, Gscheidle, T, Coppola, R, Weickert, T, Kolachana, BS, Goldman, D, Weinberger, DR (2003). Executive subprocesses in working memory: relationship to catechol-O-methyltransferase Val158Met genotype and schizophrenia. Archives of General Psychiatry 60, 889–896.Google Scholar
Goswami, U, Gulrajani, C, Moore, PB, Varma, A, Young, AH, Khastgir, U, Sharma, AN (2002). Neurocognitive decline in bipolar mood disorder: role of mood stabilizers. Journal of Psychopharmacology 16, A45.Google Scholar
Goswami, U, Sharma, A, Khastigir, U, Ferrier, IN, Young, AH, Gallagher, P, Thompson, JM, Moore, PB (2006). Neuropsychological dysfunction, soft neurological signs and social disability in euthymic patients with bipolar disorder. British Journal of Psychiatry 188, 366–373.Google Scholar
Gottesman, II, Gould, TD (2003). The endophenotype concept in psychiatry: etymology and strategic intentions. American Journal of Psychiatry 160, 636–645.Google Scholar
Gourovitch, ML, Torrey, EF, Gold, JM, Randolph, C, Weinberger, DR, Goldberg, TE (1999). Neuropsychological performance of monozygotic twins discordant for bipolar disorder. Biological Psychiatry 45, 639–646.Google Scholar
Green, EK, Raybould, R, Macgregor, S, Gordon-Smith, K, Heron, J, Hyde, S, Grozeva, D, Hamshere, M, Williams, N, Owen, MJ, O'Donovan, MC, Jones, L, Jones, I, Kirov, G, Craddock, N (2005). Operation of the schizophrenia susceptibility gene, neuregulin 1, across traditional diagnostic boundaries to increase risk for bipolar disorder. Archives of General Psychiatry 62, 642–648.Google Scholar
Grober, E, Sliwinski, M (1991). Development and validation of a model for estimating premorbid verbal intelligence in the elderly. Journal of Clinical and Experimental Neuropsychology 19, 933–949.Google Scholar
Harkavy-Friedman, JM, Keilp, JG, Grunebaum, MF, Sher, L, Printz, D, Burke, AK, Mann, JJ, Oquendo, M (2006). Are BPI and BPII suicide attempters distinct neuropsychologically? Journal of Affective Disorders 94, 255–259.Google Scholar
Harrison, PJ, Law, AJ (2006). Neuregulin 1 and schizophrenia: genetics, gene expression, and neurobiology. Biological Psychiatry 60, 132–140.Google Scholar
Hasler, G, Drevets, WC, Gould, TD, Gottesman, II, Manji, HK (2006). Toward constructing an endophenotype strategy for bipolar disorders. Biological Psychiatry 60, 93–105.Google Scholar
Heaton, RK (1981). A Manual for the Wisconsin Card Sorting Test. Psychological Assessment Resources: Odessa, FL.Google Scholar
Heydebrand, G (2006). Cognitive deficits in the families of patients with schizophrenia. Current Opinion in Psychiatry 19, 277–281.Google Scholar
Kéri, S, Kelemen, O, Benedek, G, Janka, Z (2001). Different trait markers for schizophrenia and bipolar disorder: a neurocognitive approach. Psychological Medicine 31, 915–922.Google Scholar
Kieseppa, T, Tuulio-Henriksson, A, Haukka, J, Van Erp, T, Glahn, D, Cannon, TD, Partonen, T, Kaprio, J, Lonnqvist, J (2005). Memory and verbal learning functions in twins with bipolar-I disorder, and the role of information-processing speed. Psychological Medicine 35, 205–215.Google Scholar
Krabbendam, L, Arts, B, van Os, J, Aleman, A (2005). Cognitive functioning in patients with schizophrenia and bipolar disorder: a quantitative review. Schizophrenia Research 80, 137–149.Google Scholar
Krabbendam, L, Honig, A, Wiersma, J, Vuurman, EF, Hofman, PA, Derix, MM, Nolen, WA, Jolles, J (2000). Cognitive dysfunctions and white matter lesions in patients with bipolar disorder in remission. Acta Psychiatrica Scandinavica 101, 274–280.Google Scholar
Kremen, WS, Faraone, SV, Seidman, LJ, Pepple, JR, Tsuang, MT (1998). Neuropsychological risk indicators for schizophrenia: a preliminary study of female relatives of schizophrenic and bipolar probands. Psychiatry Research 79, 227–240.Google Scholar
Kurtz, MM, Ragland, JD, Bilker, W, Gur, RC, Gur, RE (2001). Comparison of the continuous performance test with and without working memory demands in healthy controls and patients with schizophrenia. Schizophrenia Research 48, 307–316.Google Scholar
Larson, ER, Shear, PK, Krikorian, R, Welge, J, Strakowski, SM (2005). Working memory and inhibitory control among manic and euthymic patients with bipolar disorder. Journal of the International Neuropsychological Society 11, 163–172.Google Scholar
Lezak, MD (1995). Neuropsychological Assessment. Oxford University Press: New York.Google Scholar
Malhi, GS, Lagopoulos, J, Sachdev, PS, Ivanovski, B, Shnier, R (2005). An emotional Stroop functional MRI study of euthymic bipolar disorder. Bipolar Disorders 7 (Suppl. 5), 58–69.Google Scholar
Martinez-Aran, A, Vieta, E, Reinares, M, Colom, F, Torrent, C, Sanchez-Moreno, J, Benabarre, A, Goikolea, JM, Comes, M, Salamero, M (2004). Cognitive function across manic or hypomanic, depressed, and euthymic states in bipolar disorder. American Journal of Psychiatry 161, 262–270.Google Scholar
Mata, I, Arranz, MJ, Staddon, S, Lopez-Ilundain, JM, Tabares-Seisdedos, R, Murray, RM (2006). The high-activity Val allele of the catechol-O-methyltransferase gene predicts greater cognitive deterioration in patients with psychosis. Psychiatric Genetics 16, 213–216.Google Scholar
McIntosh, AM, Harrison, LK, Forrester, K, Lawrie, SM, Johnstone, EC (2005). Neuropsychological impairments in people with schizophrenia or bipolar disorder and their unaffected relatives. British Journal of Psychiatry 186, 378–385.Google Scholar
Minzenberg, MJ, Xu, K, Mitropoulou, V, Harvey, PD, Finch, T, Flory, JD, New, AS, Goldman, D, Siever, LJ (2006). Catechol-O-methyltransferase Val158Met genotype variation is associated with prefrontal-dependent task performance in schizotypal personality disorder patients and comparison groups. Psychiatric Genetics 16, 117–124.Google Scholar
Murray, RM, Sham, P, Van Os, J, Zanelli, J, Cannon, M, McDonald, C (2004). A developmental model for similarities and dissimilarities between schizophrenia and bipolar disorder. Schizophrenia Research 71, 405–416.Google Scholar
Nehra, R, Chakrabarti, S, Pradhan, BK, Khehra, N (2006). Comparison of cognitive functions between first- and multi-episode bipolar affective disorders. Journal of Affective Disorders 93, 185–192.Google Scholar
Newcomer, JW (2006). Medical risk in patients with bipolar disorder and schizophrenia. Journal of Clinical Psychiatry 67 (Suppl. 9), 25–30.Google Scholar
Pirkola, T, Tuulio-Henriksson, A, Glahn, D, Kieseppa, T, Haukka, J, Kaprio, J, Lonnqvist, J, Cannon, TD (2005). Spatial working memory function in twins with schizophrenia and bipolar disorder. Biological Psychiatry 58, 930–936.Google Scholar
Porteous, DJ, Thomson, P, Brandon, NJ, Millar, JK (2006). The genetics and biology of DISC1 – an emerging role in psychosis and cognition. Biological Psychiatry 60, 123–131.Google Scholar
Reitan, RM (1958). Validity of the Trail Making Test as an indicator of organic brain damage. Perceptual and Motor Skills 8, 271–276.Google Scholar
Rey, A (1941). Psychological examination in cases of traumatic encephalopathy: problems [in French]. Archives de Psychologie 28, 215–285.Google Scholar
Rey, A (1964). L'Examen Psychologique dans les Cas d'Encephalopathie Traumatique. Presses Universitaires de France: Paris.Google Scholar
Robinson, LJ, Ferrier, IN (2006). Evolution of cognitive impairment in bipolar disorder: a systematic review of cross-sectional evidence. Bipolar Disorders 8, 103–116.Google Scholar
Robinson, LJ, Thompson, JM, Gallagher, P, Goswami, U, Young, AH, Ferrier, IN, Moore, PB (2006). A meta-analysis of cognitive deficits in euthymic patients with bipolar disorder. Journal of Affective Disorders 93, 105–115.Google Scholar
Rosa, A, Peralta, V, Cuesta, MJ, Zarzuela, A, Serrano, F, Martinez-Larrea, A, Fananas, L (2004). New evidence of association between COMT gene and prefrontal neurocognitive function in healthy individuals from sibling pairs discordant for psychosis. American Journal of Psychiatry 161, 1110–1112.Google Scholar
Ross, CA, Margolis, RL, Reading, SA, Pletnikov, M, Coyle, JT (2006). Neurobiology of schizophrenia. Neuron 52, 139–153.Google Scholar
Savitz, J, Solms, M, Ramesar, R (2005 a). Neuropsychological dysfunction in bipolar affective disorder: a critical opinion. Bipolar Disorders 7, 216–235.Google Scholar
Savitz, JB, Solms, M, Ramesar, RS (2005 b). Neurocognitive function as an endophenotype for genetic studies of bipolar affective disorder. Neuromolecular Medicine 7, 275–286.Google Scholar
Schillo, S, Pejovic, V, Hunzinger, C, Hansen, T, Poznanovic, S, Kriegsmann, J, Schmidt, WJ, Schrattenholz, A (2005). Integrative proteomics: functional and molecular characterization of a particular glutamate-related neuregulin isoform. Journal of Proteome Research 4, 900–908.Google Scholar
Schubert, EW, McNeil, TF (2005). Neuropsychological impairment and its neurological correlates in adult offspring with heightened risk for schizophrenia and affective psychosis. American Journal of Psychiatry 162, 758–766.Google Scholar
Scolnick, EM, Petryshen, T, Sklar, P (2006). Schizophrenia: do the genetics and neurobiology of neuregulin provide a pathogenesis model? Harvard Review of Psychiatry 14, 64–77.Google Scholar
Sitskoorn, MM, Aleman, A, Ebisch, SJ, Appels, MC, Kahn, RS (2004). Cognitive deficits in relatives of patients with schizophrenia: a meta-analysis. Schizophrenia Research 71, 285–295.Google Scholar
Snitz, BE, Macdonald, AW 3rd, Carter, CS (2006). Cognitive deficits in unaffected first-degree relatives of schizophrenia patients: a meta-analytic review of putative endophenotypes. Schizophrenia Bulletin 32, 179–194.Google Scholar
Sobczak, S, Honig, A, Schmitt, JA, Riedel, WJ (2003). Pronounced cognitive deficits following an intravenous l-tryptophan challenge in first-degree relatives of bipolar patients compared to healthy controls. Neuropsychopharmacology 28, 711–719.Google Scholar
Strakowski, SM, Adler, CM, Holland, SK, Mills, N, DelBello, MP (2004). A preliminary FMRI study of sustained attention in euthymic, unmedicated bipolar disorder. Neuropsychopharmacology 29, 1734–1740.Google Scholar
Strakowski, SM, Delbello, MP, Adler, CM (2005). The functional neuroanatomy of bipolar disorder: a review of neuroimaging findings. Molecular Psychiatry 10, 105–116.Google Scholar
Stroop, JR (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology 18, 643–662.Google Scholar
Szoke, A, Schurhoff, F, Golmard, JL, Alter, C, Roy, I, Meary, A, Etain, B, Bellivier, F, Leboyer, M (2006). Familial resemblance for executive functions in families of schizophrenic and bipolar patients. Psychiatry Research 144, 131–138.Google Scholar
Szoke, A, Schurhoff, F, Mathieu, F, Meary, A, Ionescu, S, Leboyer, M (2005). Tests of executive functions in first-degree relatives of schizophrenic patients: a meta-analysis. Psychological Medicine 35, 771–782.Google Scholar
Thompson, JM, Gallagher, P, Hughes, JH, Watson, S, Gray, JM, Ferrier, IN, Young, AH (2005). Neurocognitive impairment in euthymic patients with bipolar affective disorder. British Journal of Psychiatry 186, 32–40.Google Scholar
Thompson, JM, Hamilton, CJ, Gray, JM, Quinn, JG, Mackin, P, Young, AH, Ferrier, IN (2006). Executive and visuospatial sketchpad resources in euthymic bipolar disorder: implications for visuospatial working memory architecture. Memory 14, 437–451.Google Scholar
Torrent, C, Martinez-Aran, A, Daban, C, Sanchez-Moreno, J, Comes, M, Goikolea, JM, Salamero, M, Vieta, E (2006). Cognitive impairment in bipolar II disorder. British Journal of Psychiatry 189, 254–259.Google Scholar
Toulopoulou, T, Quraishi, S, McDonald, C, Murray, RM (2006). The Maudsley Family Study: premorbid and current general intellectual function levels in familial bipolar I disorder and schizophrenia. Journal of Clinical and Experimental Neuropsychology 28, 243–259.Google Scholar
Tunbridge, EM, Harrison, PJ, Weinberger, DR (2006). Catechol-o-methyltransferase, cognition, and psychosis: Val158Met and beyond. Biological Psychiatry 60, 141–151.Google Scholar
van Gorp, WG, Altshuler, L, Theberge, DC, Wilkins, J, Dixon, W (1998). Cognitive impairment in euthymic bipolar patients with and without prior alcohol dependence. A preliminary study. Archives of General Psychiatry 55, 41–46.Google Scholar
Varga, M, Magnusson, A, Flekkoy, K, Ronneberg, U, Opjordsmoen, S (2006). Insight, symptoms and neurocognition in bipolar I patients. Journal of Affective Disorders 91, 1–9.Google Scholar
Wechsler, D (1955). Wechsler Adult Intelligence Scale (Manual). Psychological Corporation: New York.Google Scholar
Wechsler, D (1981). Wechsler Adult Intelligence Scale – Revised. Psychological Corporation: New York.Google Scholar
Woodward, ND, Jayathilake, K, Meltzer, HY (2007). COMT Val108/158Met genotype, cognitive function, and cognitive improvement with clozapine in schizophrenia. Schizophrenia Research 90, 86–96.Google Scholar
Yurgelun-Todd, DA, Ross, AJ (2006). Functional magnetic resonance imaging studies in bipolar disorder. CNS Spectrums 11, 287–297.Google Scholar
Zalla, T, Joyce, C, Szoke, A, Schurhoff, F, Pillon, B, Komano, O, Perez-Diaz, F, Bellivier, F, Alter, C, Dubois, B, Rouillon, F, Houde, O, Leboyer, M (2004). Executive dysfunctions as potential markers of familial vulnerability to bipolar disorder and schizophrenia. Psychiatry Research 121, 207–217.Google Scholar
Zubieta, JK, Huguelet, P, O'Neil, RL, Giordani, BJ (2001). Cognitive function in euthymic bipolar I disorder. Psychiatry Research 102, 9–20.Google Scholar