A dimensional approach to the psychosis spectrum between bipolar disorder and schizophrenia: The Schizo-Bipolar Scale

Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, United States.
Schizophrenia Research (Impact Factor: 3.92). 12/2011; 133(1-3):250-4. DOI: 10.1016/j.schres.2011.09.005
Source: PubMed


There is increasing evidence for phenomenological, biological and genetic overlap between schizophrenia and bipolar disorder, bringing into question the traditional dichotomy between them. Neurobiological models linked to dimensional clinical data may provide a better foundation to represent diagnostic variation in neuropsychiatric disorders.
To capture the interaction between psychosis and affective symptoms dimensionally, we devised a brief descriptive scale based on the type and relative proportions of psychotic and affective symptoms over the illness course. The scale was administered to a series of 762 patients with psychotic disorders, including schizophrenia, schizoaffective and psychotic bipolar disorder assessed as part of the Bipolar-Schizophrenia Network for Intermediate Phenotypes (B-SNIP) study.
The resulting Schizo-Bipolar Scale scores across these disorders showed neither a clear dichotomy nor a simple continuous distribution. While the majority of cases had ratings close to prototypic schizophrenia or bipolar disorder, a large group (45% of cases) fell on the continuum between these two prototypes.
Our data suggest a hybrid conceptualization model with a representation of cases with prototypic schizophrenia or bipolar disorder at the extremes, but a large group of patients on the continuum between them that traditionally would be considered schizoaffective. A dimensional approach, using the Schizo-Bipolar Scale, characterized patients across a spectrum of psychopathology. This scale may provide a valuable means to examine the relationships between schizophrenia and psychotic bipolar disorder.

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    • "Because acute illness may disrupt inhibitory control in bipolar disorder (Strakowski et al., 2010) and schizophrenia (Harris et al., 2006; Hill et al., 2009), patients were clinically stable and on consistent psychopharmacological treatment for at least one month. Symptom severity and functioning were rated using the Positive and Negative Symptom Scale (Lancon et al., 2000), Young Mania Rating Scale (Young et al., 2000), Montgomery–Asberg Depression Rating Scale (Montgomery and Asberg, 1979), Birchwood Social Functioning Scale (Birchwood et al., 1990), Schizo-bipolar Scale (Keshavan et al., 2011) and Barratt Impulsiveness Scale 11 (Patton et al., 1995). All but 37 patients were taking psychotropic medications (Table 1). "
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    ABSTRACT: Difficulty inhibiting context-inappropriate behavior is a common deficit in psychotic disorders. The diagnostic specificity of this impairment, its familiality, and its degree of independence from the generalized cognitive deficit associated with psychotic disorders remain to be clarified. Schizophrenia, schizoaffective and bipolar patients with history of psychosis (n=523), their available first-degree biological relatives (n=656), and healthy participants (n=223) from the multi-site B-SNIP study completed a manual Stop Signal task. A nonlinear mixed model was used to fit logistic curves to success rates on Stop trials as a function of parametrically varied Stop Signal Delay. While schizophrenia patients had greater generalized cognitive deficit than bipolar patients, their deficits were similar on the Stop Signal task. Further, only bipolar patients showed impaired inhibitory control relative to healthy individuals after controlling for generalized cognitive deficit. Deficits accounted for by the generalized deficit were seen in relatives of schizophrenia and schizoaffective patients, but not in relatives of bipolar patients. In clinically stable patients with psychotic bipolar disorder, impaired inhibitory behavioral control was a specific cognitive impairment, distinct from the generalized neuropsychological impairment associated with psychotic disorders. Thus, in bipolar disorder with psychosis, a deficit in inhibitory control may contribute to risk for impulsive behavior. Because the deficit was not familial in bipolar families and showed a lack of independence from the generalized cognitive deficit in schizophrenia spectrum disorders, it appears to be a trait related to illness processes rather than one tracking familial risk factors.
    Schizophrenia Research 09/2014; 159(2-3). DOI:10.1016/j.schres.2014.08.025 · 3.92 Impact Factor
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    • "Clinical symptoms were rated using the Positive and Negative Syndrome Scale (PANSS) (Kay et al., 1986), the Montgomery–Åsberg Depression Rating Scale (MADRS) (Montgomery and Asberg, 1979), and the Young Mania Rating Scale (YMRS) (Young et al., 1978), and functional status was assessed with the Social Functioning Scale (SFS) (Birchwood et al., 1990). To assess a dimension of psychotic illness ranging from prototypical SCZ to BD, ratings were made using the Schizo-Bipolar Scale (Keshavan et al., 2011). "
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    ABSTRACT: Difficulty recognizing facial emotions is an important social-cognitive deficit associated with psychotic disorders. It also may reflect a familial risk for psychosis in schizophrenia-spectrum disorders and bipolar disorder.
    Schizophrenia Research 07/2014; 158(1-3). DOI:10.1016/j.schres.2014.07.001 · 3.92 Impact Factor
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    • "The neurobiological continuum linking the two psychotic illnesses – schizophrenia and bipolar disorder – is elusive despite two decades of rapid advance in neuroscientific methods (Keshavan et al. 2011; Kaur et al. 2012). In the past, neuroimaging studies have mostly focused on trying to differentiate between schizophrenia spectrum and bipolar disorder, by aiming to identify disease-specific mechanisms in each of these disorders (Curtis et al. 2001; Costafreda et al. 2009; Whalley et al. 2009; Hall et al. 2010). "
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