Duncan McLean

University of Queensland , Brisbane, Queensland, Australia

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Publications (16)80.6 Total impact

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    ABSTRACT: There is significant variation in the expression of schizophrenia across ethnically different populations, and the optimal structural and diagnostic representation of schizophrenia are contested. We contrasted both lifetime frequencies of DSM-IV criterion A (the core symptom criterion of the internationally recognized DSM classification system) symptoms and types/content of delusions and hallucinations in transethnic schizophrenia populations from Australia (n = 776), India (n = 504) and Sarawak, Malaysia (n = 259), to elucidate clinical heterogeneity. Differences in both criterion A symptom composition and symptom content were apparent. Indian individuals with schizophrenia reported negative symptoms more frequently than other sites, whereas individuals from Sarawak reported disorganized symptoms more frequently. Delusions of control and thought broadcast, insertion, or withdrawal were less frequent in Sarawak than Australia. Curiously, a subgroup of 20 Indian individuals with schizophrenia reported no lifetime delusions or hallucinations. These findings potentially challenge the long-held view in psychiatry that schizophrenia is fundamentally similar across cultural groups, with differences in only the content of psychotic symptoms, but equivalence in structural form.
    Culture Medicine and Psychiatry 07/2014; · 1.29 Impact Factor
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    ABSTRACT: Schizophrenia is a severe debilitating brain disorder with a poorly understood aetiology. Among the diverse aetiological clues lies evidence for immune abnormalities in some individuals. The aim of this study was to investigate the frequency and specificity of autoantibodies directed against the brain in people with schizophrenia. Sera were screened for reactivity against human brain tissue (hippocampus and prefrontal cortex). Neuronal cell body and filamentous patterns of brain tissue staining were observed significantly more frequently in sera from schizophrenia patients (n = 30) compared to controls (n = 24). Sera that showed a neuronal cell body pattern of staining on hippocampus reacted strongly to an extracellular epitope of the M1 muscarinic acetylcholine receptor (m1AChR) in ELISA. Both cell body staining and elevated m1AChR reactivity correlated with higher symptom scores for poverty of speech. Sera showing a filamentous staining pattern predominantly targetted microfilaments, intermediate filaments or neurofilaments, particularly neurofilament medium (NFM), which is a dopamine receptor interacting protein. By ELISA, there was strongly elevated reactivity against NFM in a subset (15%) of schizophrenia patients (n = 101) compared to healthy controls (n = 55) or patients with multiple sclerosis (n = 32). These results support the hypothesis that neurotransmitter receptors or molecules involved in regulation of neurotransmission are targets of autoantibodies in some people with schizophrenia.
    Journal of neuroimmunology 04/2014; · 2.84 Impact Factor
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    ABSTRACT: The symptom profile of schizophrenia can vary between ethnic groups. We explored selected symptom variables previously reported to be characteristic of schizophrenia in the Iban of Sarawak in transethnic populations from Australia, India, and Sarawak, Malaysia. We tested site differences to confirm previous research, and to explore implications of differences across populations for future investigations. We recruited schizophrenia samples in Australia (n = 609), India (n = 310) and Sarawak (n = 205) primarily for the purposes of genetic studies. We analyzed seven identified variables and their relationship to site using logistic regression, including: global delusions, bizarre delusions, thought broadcast/insertion/withdrawal delusions, global hallucinations, auditory hallucinations, disorganized behavior, and prodromal duration. We identified a distinct symptom profile in our Sarawak sample. Specifically, the Iban exhibit: low frequency of thought broadcast/insertion/withdrawal delusions, high frequency of auditory hallucinations and disorganized behavior, with a comparatively short prodrome when compared with Australian and Indian populations. Understanding between-site variation in symptom profile may complement future transethnic genetic studies, and provide important clues as to the nature of differing schizophrenia expression across ethnically distinct groups. A comprehensive approach to subtyping schizophrenia is warranted, utilizing comprehensively ascertained transethnic samples to inform both schizophrenia genetics and nosology.
    Asia-Pacific Psychiatry 08/2013; · 0.47 Impact Factor
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    ABSTRACT: We contrasted demographic and clinical characteristics in transethnic schizophrenia populations from Australia (n=821), India (n=520) and Sarawak, Malaysia (n=298) and proposed cultural explanations for identified site differences. From these we aimed to identify candidate variables free from significant cultural confounding that are hence suitable for inclusion in genetic analyses. We observed five phenomena: (1) more individuals were living alone in Australia than India or Sarawak; (2) drug use was lower in India than Australia or Sarawak; (3) duration of untreated psychosis (DUP) was longer in India than Australia or Sarawak; (4) the rate of schizoaffective disorder was lower in India than Australia or Sarawak; and (5) age at psychosis onset (AAO) was older in Sarawak than Australia or India. We suggest that site differences for living arrangements, drug use and DUP are culturally confounded. The schizoaffective site difference likely results from measurement bias. The AAO site difference, however, has no obvious cultural or measurement bias explanation. Therefore, this may be an ideal candidate for use in genetic studies, given that genetic variants affecting AAO have already been proposed.
    Psychiatry Research 03/2012; 196(2-3):194-200. · 2.68 Impact Factor
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    Duncan McLean, Beverley Gladman, Bryan Mowry
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    ABSTRACT: Suicide and attempted suicide are common in individuals with schizophrenia, and evidence exists for a link between substance use disorders and suicidality in this disorder. However, alcohol has not been consistently implicated. We examined the relationship between substance use disorders and suicide attempts in schizophrenia. We recruited a schizophrenia sample in Australia (n = 821) for genetic analyses. We analysed demographic and clinical variables, including substance use disorders, and their relationship to suicide attempts using generalised equation modelling. A significant association was identified between lifetime alcohol abuse/dependence and suicide attempts (OR = 1.66; 95% CI, 1.23 to 2.24; p = 0.001) after adjustment for potential confounders, but not between cannabis abuse/dependence and suicide attempts, nor between other illicit drug abuse/dependence and suicide attempts. Polysubstance abuse/dependence was also not implicated. These results suggest that the presence of alcohol abuse/dependence may be a risk factor for suicide attempts in individuals with schizophrenia, independent of comorbid substance abuse/dependence.
    Australian and New Zealand Journal of Psychiatry 02/2012; 46(2):132-40. · 3.77 Impact Factor
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    ABSTRACT: We examined the role of common genetic variation in schizophrenia in a genome-wide association study of substantial size: a stage 1 discovery sample of 21,856 individuals of European ancestry and a stage 2 replication sample of 29,839 independent subjects. The combined stage 1 and 2 analysis yielded genome-wide significant associations with schizophrenia for seven loci, five of which are new (1p21.3, 2q32.3, 8p23.2, 8q21.3 and 10q24.32-q24.33) and two of which have been previously implicated (6p21.32-p22.1 and 18q21.2). The strongest new finding (P = 1.6 × 10(-11)) was with rs1625579 within an intron of a putative primary transcript for MIR137 (microRNA 137), a known regulator of neuronal development. Four other schizophrenia loci achieving genome-wide significance contain predicted targets of MIR137, suggesting MIR137-mediated dysregulation as a previously unknown etiologic mechanism in schizophrenia. In a joint analysis with a bipolar disorder sample (16,374 affected individuals and 14,044 controls), three loci reached genome-wide significance: CACNA1C (rs4765905, P = 7.0 × 10(-9)), ANK3 (rs10994359, P = 2.5 × 10(-8)) and the ITIH3-ITIH4 region (rs2239547, P = 7.8 × 10(-9)).
    Nature Genetics 09/2011; 43(10):969-76. · 35.21 Impact Factor
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    ABSTRACT: No Yes
    01/2011;
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    Advances in Mental Health 01/2011;
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    ABSTRACT: Identifying susceptibility genes for schizophrenia may be complicated by phenotypic heterogeneity, with some evidence suggesting that phenotypic heterogeneity reflects genetic heterogeneity. To evaluate the heritability and conduct genetic linkage analyses of empirically derived, clinically homogeneous schizophrenia subtypes. Latent class and linkage analysis. Taiwanese field research centers. The latent class analysis included 1236 Han Chinese individuals with DSM-IV schizophrenia. These individuals were members of a large affected-sibling-pair sample of schizophrenia (606 ascertained families), original linkage analyses of which detected a maximum logarithm of odds (LOD) of 1.8 (z = 2.88) on chromosome 10q22.3. Multipoint exponential LOD scores by latent class assignment and parametric heterogeneity LOD scores. Latent class analyses identified 4 classes, with 2 demonstrating familial aggregation. The first (LC2) described a group with severe negative symptoms, disorganization, and pronounced functional impairment, resembling "deficit schizophrenia." The second (LC3) described a group with minimal functional impairment, mild or absent negative symptoms, and low disorganization. Using the negative/deficit subtype, we detected genome-wide significant linkage to 1q23-25 (LOD = 3.78, empiric genome-wide P = .01). This region was not detected using the DSM-IV schizophrenia diagnosis, but has been strongly implicated in schizophrenia pathogenesis by previous linkage and association studies.Variants in the 1q region may specifically increase risk for a negative/deficit schizophrenia subtype. Alternatively, these results may reflect increased familiality/heritability of the negative class, the presence of multiple 1q schizophrenia risk genes, or a pleiotropic 1q risk locus or loci, with stronger genotype-phenotype correlation with negative/deficit symptoms. Using the second familial latent class, we identified nominally significant linkage to the original 10q peak region. Genetic analyses of heritable, homogeneous phenotypes may improve the power of linkage and association studies of schizophrenia and thus have relevance to the design and analysis of genome-wide association studies.
    Archives of general psychiatry 10/2009; 66(10):1058-67. · 12.26 Impact Factor
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    ABSTRACT: Associations between a single-nucleotide polymorphism (SNP) in exon 1 of the cytotoxic T-lymphocyte antigen-4 (CTLA4) gene and schizophrenia in a Korean population have been previously described. The current study investigated whether a similar link occurs in a Caucasian population with schizophrenia. One hundred and twenty-two age- and sex-matched pairs of people with DSM-III-R diagnosis of schizophrenia and healthy controls were included in this study. Three previously described SNPs (from the promoter, exon 1 and 3' UTR) of the CTLA4 gene were analysed. In the entire sample, we detected no allelic or genotypic association for any of the three SNPs. Given documented gender differences in incidence of schizophrenia, we conducted separate analyses of male and female participants. In males, both the promoter region SNP (-318C/T) and the 3' UTR SNP demonstrated nominally significant association with schizophrenia. The 3' UTR SNP remained significant following correction for multiple testing (permuted P=0.046). In addition, all possible haplogenotypes showed significant association with disease in males with two--both containing the 3' UTR SNP--remaining significant following correction for the genotypic tests of all SNPs and haplogenotypes in males. These results suggest a role for the 3' UTR SNP and/or variants in high linkage disequilibrium with this SNP in the pathogenesis of schizophrenia.
    Brain Behavior and Immunity 10/2008; 23(3):347-50. · 5.61 Impact Factor
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    ABSTRACT: Lymphoblastoid cell lines (LCLs) and fibroblasts provide conveniently derived non-neuronal samples in which to investigate the aetiology of schizophrenia (SZ) using gene expression profiling. This assumes that heritable mechanisms associated with risk of SZ have systemic effects and result in changes to gene expression in all tissues. The broad aim of this and other similar studies is that comparison of the transcriptomes of non-neuronal tissues from SZ patients and healthy controls may identify gene/pathway dysregulation underpinning the neurobiological defects associated with SZ. Using microarrays consisting of 18,664 probes we compared gene expression profiles of LCLs from SZ cases and healthy controls. To identify robust associations with SZ that were not patient or tissue specific, we also examined fibroblasts from an independent series of SZ cases and controls using the same microarrays. In both tissue types ANOVA analysis returned approximately the number of differentially expressed genes expected by chance. No genes were significantly differentially expressed in either tissue when corrected for multiple testing. Even using relaxed parameters (p < or = 0.05, without multiple testing correction) there were still no differentially expressed genes that also displayed > or = 2-fold change between the groups of SZ cases and controls common to both LCLs and fibroblasts. We conclude that despite encouraging data from previous microarray studies assessing non-neural tissues, the lack of a convergent set of differentially expressed genes associated with SZ using fibroblasts and LCLs indicates the utility of non-neuronal tissues for detection of gene expression differences and/or pathways associated with SZ remains to be demonstrated.
    PLoS ONE 01/2008; 3(6):e2412. · 3.53 Impact Factor
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    ABSTRACT: The aim of this study was to investigate whether there is an increased susceptibility to apoptosis in cultured fibroblasts from patients with schizophrenia. Dermal fibroblasts were collected and cultured from three groups: patients with schizophrenia, patients with non-schizophrenic psychosis, and healthy comparison subjects. Susceptibility to apoptosis was measured at the level of degradation product (proportion of cells in the sub-G0 cell cycle fraction in which apoptotic bodies accumulate), pro-apoptotic effector (activated caspase-3), and molecular regulators (P53, Bax and Bcl-2). Cell lines were studied under both basal culture and cycloheximide (an apoptotic inducer) exposure conditions. Consistent with increased susceptibility to apoptosis, the proportion of sub-G0 cells under basal conditions was significantly larger in the schizophrenia group, compared to the non-schizophrenic psychosis group. However when apoptosis was stimulated with cycloheximide, the schizophrenia group showed an attenuated caspase-3 response. The pattern of correlations between regulators, caspase-3 and the proportion of sub-G0 cells was different in the schizophrenia group, consistent with group-specific apoptotic pathway dysregulation. The study demonstrated anomalous apoptotic mechanisms in schizophrenia, which appear not to affect non-schizophrenia psychosis patients. The detection of these anomalies in fibroblasts suggests that altered apoptosis may be observable in all somatic cell types in schizophrenia.
    Schizophrenia Research 06/2006; 84(1):20-8. · 4.59 Impact Factor
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    ABSTRACT: We previously demonstrated that olfactory cultures from individuals with schizophrenia had increased cell proliferation compared to cultures from healthy controls. The aims of this study were to (a) replicate this observation in a new group of individuals with schizophrenia, (b) examine the specificity of these findings by including individuals with bipolar I disorder and (c) explore gene expression differences that may underlie cell cycle differences in these diseases. Compared to controls (n = 10), there was significantly more mitosis in schizophrenia patient cultures (n = 8) and significantly more cell death in the bipolar I disorder patient cultures (n = 8). Microarray data showed alterations to the cell cycle and phosphatidylinositol signalling pathways in schizophrenia and bipolar I disorder, respectively. Whilst caution is required in the interpretation of the array results, the study provides evidence indicating that cell proliferation and cell death in olfactory neuroepithelial cultures is differentially altered in schizophrenia and bipolar disorder.
    Schizophrenia Research 03/2006; 82(2-3):163-73. · 4.59 Impact Factor
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    ABSTRACT: Deficits in olfactory identification have been demonstrated in patients with schizophrenia. This study examined the interaction between smoking and olfactory identification in patients with psychotic disorders versus well controls. Olfactory identification was assessed in three groups of subjects using the University of Pennsylvania Smell Identification Test (UPSIT). Sixteen patients with affective psychoses, 22 patients with nonaffective psychoses, and 21 well controls were tested. There was a significant interaction between diagnostic classification (patient or control) and smoking. Patients who were smokers scored higher on the UPSIT than non-smokers, while controls who were smokers scored lower than non-smokers. Smoking may have a 'normalising' effect on olfactory identification in some patients with psychosis. Further studies are needed to examine the relationship between psychosis, olfactory identification and the effects of nicotine.
    Australian and New Zealand Journal of Psychiatry 01/2004; 38(1-2):81-3. · 3.77 Impact Factor

Publication Stats

502 Citations
80.60 Total Impact Points

Institutions

  • 2004–2012
    • University of Queensland 
      • Queensland Centre for Mental Health Research (QCMHR)
      Brisbane, Queensland, Australia
  • 2008
    • Queensland Health
      • Queensland Centre for Mental Health Research
      Brisbane, Queensland, Australia