Abstract
Objective: There is renewed debate on whether modern diagnostic classification should adopt a dichotomous or dimensional approach to schizophrenia and bipolar disorder. This study synthesizes data from voxel-based studies of schizophrenia and bipolar disorder to estimate the extent to which these conditions have a common neuroanatomical phenotype. Methods: A post-hoc meta-analytic estimation of the extent to which bipolar disorder, schizophrenia, or both conditions contribute to brain gray matter differences compared to controls was achieved using a novel application of the conventional anatomical likelihood estimation (ALE) method. 19 schizophrenia studies (651 patients and 693 controls) were matched as closely as possible to 19 bipolar studies (540 patients and 745 controls). Result: Substantial overlaps in the regions affected by schizophrenia and bipolar disorder included regions in prefrontal cortex, thalamus, left caudate, left medial temporal lobe, and right insula. Bipolar disorder and schizophrenia jointly contributed to clusters in the right hemisphere, but schizophrenia was almost exclusively associated with additional gray matter deficits (left insula and amygdala) in the left hemisphere. Limitation: The current meta-analytic method has a number of constraints. Importantly, only studies identifying differences between controls and patient groups could be included in this analysis. Conclusion: Bipolar disorder shares many of the same brain regions as schizophrenia. However, relative to neurotypical controls, lower gray matter volume in schizophrenia is more extensive and includes the amygdala. This fresh application of ALE accommodates multiple studies in a relatively unbiased comparison. Common biological mechanisms may explain the neuroanatomical overlap between these major disorders, but explaining why brain differences are more extensive in schizophrenia remains challenging.
Highlights
The Kraepelinian dichotomy between schizophrenia and bipolar disorder, otherwise classically referred to dementia praecox and manic-depressive insanity respectively, has sustained a recent and vigorous onslaught (Heckers, 2008)
23 voxel-based morphometry” (VBM) bipolar studies were found meeting our criteria (Bruno et al, 2004; Doris et al, 2004; Lochhead et al, 2004; Lyoo et al, 2004; McIntosh et al, 2004; Dickstein et al, 2005; Farrow et al, 2005; McDonald et al, 2005; Nugent et al, 2006; Adler et al, 2007; Chen et al, 2007; Yatham et al, 2007; Haldane et al, 2008; Janssen et al, 2008; Scherk et al, 2008; Almeida et al, 2009; Ha et al, 2009; Kempton et al, 2009; Stanfield et al, 2009; Li et al, 2010; Tost et al, 2010). Three of these studies could not be included since they reported no gray matter volume differences between patients and controls (Bruno et al, 2004; McDonald et al, 2005; Scherk et al, 2008), and this cannot be accommodated in anatomical likelihood estimation (ALE)
Clusters with excess gray matter volume exclusively generated from bipolar disorder were identified in the tail of caudate bilaterally and right pre/post central gyrus
Summary
The Kraepelinian dichotomy between schizophrenia and bipolar disorder, otherwise classically referred to dementia praecox and manic-depressive insanity respectively, has sustained a recent and vigorous onslaught (Heckers, 2008). Researchers typically compare a group of patients with bipolar disorder or schizophrenia with healthy controls and adopt a disease classification system such as ICD10 or DSM IV. Both conditions are intimately related, with shared genetic determinants (Lichtenstein et al, 2009) and common polygenic variants, as confirmed by the International Schizophrenia Consortium (ISC) in a genome-wide association study of 3,322 Europeans (International Schizophrenia Consortium et al, 2009). The opposing position is that bipolar disorder and schizophrenia are separate disorders which happen to trigger the same, general cognitive deficits (Bora et al, 2009)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
