Schizo-affective disorders: bipolar-unipolar subtyping. Natural history variables: a discriminant analysis approach

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

BACKGROUND

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.

METHOD

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.

RESULTS

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.

CONCLUSIONS

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.

The neuropsychology of schizophrenia

A model is proposed for integrating the neural and cognitive aspects of the positive symptoms of acute schizophrenia, using evidence from postmortem neuropathology and neurochemistry, clinical and preclinical studies of dopaminergic neurotransmission, anatomical connections between the limbic system and basal ganglia, attentional and other cognitive abnormalities underlying the positive symptoms of schizophrenia, specific animal models of some of these abnormalities, and previous attempts to model the cognitive functions of the septohippocampal system and the motor functions of the basal ganglia. Anatomically, the model emphasises the projections from the septohippocampal system, via the subiculum, and the amygdala to nucleus accumbens, and their interaction with the ascending dopaminergic projection to the accumbens. Psychologically, the model emphasises a failure in acute schizophrenia to integrate stored memories of past regularities of perceptual input with ongoing motor programs in the control of current perception. A number of recent experiments that offer support for the model are briefly described, including anatomical studies of limbic-striatal connections, studies in the rat of the effects of damage to these connections, and of the effects of amphetamine and neuroleptics, on the partial reinforcement extinction effect, latent inhibition and the Kamin blocking effect; and studies of the latter two phenomena in acute and chronic schizophrenics.

Re-evaluating the prevalence of and diagnostic composition within the broad clinical spectrum of bipolar disorders

Until recently it was believed that no more than 1% of the general population has bipolar disorder. Emerging transatlantic data are beginning to provide converging evidence for a higher prevalence of up to at least 5%. Manic states, even those with mood-incongruent features, as well as mixed (dysphoric) mania, are now formally included in both ICD-10 and DSM-IV. Mixed states occur in an average of 40% of bipolar patients over a lifetime; current evidence supports a broader definition of mixed states consisting of full-blown mania with two or more concomitant depressive symptoms. The largest increase in prevalence rates, however, is accounted for by 'softer' clinical expressions of bipolarity situated between the extremes of full-blown bipolar disorder where the person has at least one manic episode (bipolar I) and strictly defined unipolar major depressive disorder without personal or family history for excited periods. Bipolar II is the prototype for these intermediary conditions with major depressions and history of spontaneous hypomanic episodes; current evidence indicates that most hypomanias pursue a recurrent course and that their usual duration is 1-3 days, falling below the arbitrary 4-day cutoff required in DSM-IV. Depressions with antidepressant-associated hypomania (sometimes referred to as bipolar III) also appear, on the basis of extensive international research neglected by both ICD-10 and DSM-IV, to belong to the clinical spectrum of bipolar disorders. Broadly defined, the bipolar spectrum in studies conducted during the last decade accounts for 30-55% of all major depressions. Rapid-cycling, defined as alternation of depressive and excited (at least four per year), more often arise from a bipolar II than a bipolar I baseline; such cycling does not in the main appear to be a distinct clinical subtype - but rather a transient complication in 20% in the long-term course of bipolar disorder. Major depressions superimposed on cyclothymic oscillations represent a more severe variant of bipolar II, often mistaken for borderline or other personality disorders in the dramatic cluster. Moreover, atypical depressive features with reversed vegetative signs, anxiety states, as well as alcohol and substance abuse comorbidity, is common in these and other bipolar patients. The proper recognition of the entire clinical spectrum of bipolarity behind such 'masks' has important implications for psychiatric research and practice. Conditions which require further investigation include: (1) major depressive episodes where hyperthymic traits - lifelong hypomanic features without discrete hypomanic episodes - dominate the intermorbid or premorbid phases; and (2) depressive mixed states consisting of few hypomanic symptoms (i.e., racing thoughts, sexual arousal) during full-blown major depressive episodes - included in Kraepelin's schema of mixed states, but excluded by DSM-IV. These do not exhaust all potential diagnostic entities for possible inclusion in the clinical spectrum of bipolar disorders: the present review did not consider cyclic, seasonal, irritable-dysphoric or otherwise impulse-ridden, intermittently explosive or agitated psychiatric conditions for which the bipolar connection is less established. The concept of bipolar spectrum as used herein denotes overlapping clinical expressions, without necessarily implying underlying genetic homogeneity. In the course of the illness of the same patient, one often observes the varied manifestations described above - whether they be formal diagnostic categories or those which have remained outside the official nosology. Some form of life charting of illness with colored graphic representation of episodes, stressors, and treatments received can be used to document the uniquely varied course characteristic of each patient, thereby greatly enhancing clinical evaluation.

Prolactin response to thyrotropin-releasing hormone in schizoaffective depressed compared to depressed and schizophrenic men and healthy controls

Biological tests may help clarify the relationship of schizoaffective disorder to major depressive disorder (MDD) and schizophrenia (SCZ). Thyrotropin-releasing hormone (TRH), 500 micrograms, was administered intravenously to eight schizoaffective depressed (SD), ten SCZ, 23 MDD patients and 43 healthy controls (HC), all males, ages 20-66 years and drug-free. Research Diagnostic Criteria (RDC) were utilized for establishing diagnoses, Hamilton Rating Scale for Depression (HRSD) total scores were used for assessing depressive symptoms. There were no differences in dmax PRL (post-TRH prolactin peak minus baseline, mean +/- SD) amongst SD, SCZ and HC groups (27.3 +/- 5.2, 28.8 +/- 5.4 and 31.5 +/- 5.6 ng/ml respectively). Mean dmax PRL in MDD was significantly lower than each of the other three groups (17.1 +/- 2.2 ng/ml, P less than 0.05 for all). The essentially normal PRL response to TRH in SD, significantly different from MDD but similar to SCZ parallels our previous observations on the pattern of thyrotropin (TSH) response to TRH in the same diagnostic groups. These biological findings may be taken to indicate that schizoaffective disorder, depressed subtype, is closer to schizophrenia than to major depressive disorder. However, they cannot be considered definitive evidence to that effect since schizoaffective disorders are known to be quite heterogeneous, and since the utilized biological tests lack specificity.

Family history study of major psychiatric disorders and syndromes

The family history of major psychiatric disorders was examined among relatives of 193 in-patients fulfilling the Research Diagnostic Criteria (RDC) for Schizophrenia, Unspecified Functional Psychoses, Schizoaffective Disorder, Manic Disorder or Major Depressive Disorder. The morbid risk (MR) for schizophrenia was greater among the relatives of probands with non-affective psychoses whereas the MR for mania was greater among the relatives of probands with affective bipolar disorder. When major psychiatric syndromes were examined, only manic syndrome showed familial aggregation.