Generalized cognitive impairment in male adolescents with schizotypal personality disorder

Sensory gating disturbances in the spectrum: similarities and differences in schizotypal personality disorder and schizophrenia

BACKGROUND

DSM-5 places schizophrenia on a continuum from severe, chronic schizophrenia to the attenuated schizophrenia-like traits of schizotypal personality disorder (SPD), the prototypic schizophrenia-related personality disorder. SPD shares common genetic and neurobiological substrates with schizophrenia, including information processing abnormalities, although they are less marked. This is the first study to directly compare the P50 evoked electroencephalographic response-a measure of sensory gating and a neurophysiological endophenotype-between schizophrenia-spectrum groups. Two hypotheses were tested: (1) Compared with healthy controls (HCs), schizophrenia patients show reduced P50 suppression and SPD patients resemble schizophrenia but exhibit less marked deficits; and (2) Deficient P50 suppression in SPD is associated with greater clinical symptom severity.

METHODS

P50 was assessed in 32 schizophrenia-spectrum disorder patients (12 SPD, 20 schizophrenia patients) and 25 demographically-matched HCs. The standard conditioning (C)-testing (T) paradigm was used and P50 suppression was quantified using the T-C difference and the T/C ratio.

RESULTS

All P50 measures showed a linear, stepwise pattern with the SPD group intermediate between the HC and schizophrenia groups. Compared with HCs, both patient groups had lower conditioning and T-C difference values. Among the SPD group, greater clinical symptom severity was associated with greater conditioning-response amplitude deficits.

CONCLUSION

These findings: (1) are novel in showing that P50 deficits in SPD resemble those observed in schizophrenia, albeit less marked; (2) support the concept that the phenomenological link between SPD and schizophrenia lies in shared neurocognitive/neurophysiological pathologies; and (3) provide evidence that P50 is a neurophysiological endophenotype for schizophrenia-spectrum disorders.

Cognitive function and symptoms in adolescents with schizotypal personality disorder

Cognitive deficits have been documented in schizophrenia and spectrum disorders. This study examines cognitive functioning and its relation to symptoms in adolescents with schizotypal personality disorder (SPD). Participants are 89 adolescents recruited for a study of youth at risk for Axis I disorders, especially psychosis. At intake, 34 met criteria for SPD, 38 for another Axis II disorder and/or conduct disorder (Other disorder-OD), and 17 did not currently meet criteria for any DSM-IV disorder (normal control-NC). At initial assessment, cognitive functioning was measured using subtests from the Wechsler Intelligence Scales and Wechsler Memory Scales (WMS), and symptoms were measured using the Structured Interview for Prodromal Symptoms (SIPS). At the time of this report, 50 were readministered the SIPS at 1-year follow-up (T2). The SPD group scored significantly below the NC group on the Arithmetic subtest of the Wechsler Intelligence Scales, but there was only limited evidence of group differences on the WMS. Poorer performance on the Wechsler Intelligence Scales was associated with greater severity of negative and disorganized symptoms. Deficits on the WMS were linked with more severe disorganized symptoms. The findings reported here are consistent with previous reports of limited cognitive deficits in adolescents with SPD, with the most marked deficits in mental arithmetic. The associations between symptoms and cognitive scores parallel those observed in adults with schizophrenia and spectrum disorder, and they are consistent with the notion that negative symptoms are more stable and partially reflect premorbid cognitive functions.

How does studying schizotypal personality disorder inform us about the prodrome of schizophrenia?

An increasing emphasis in the schizophrenia literature has been on the prodromal phase of the illness. The study of schizophrenia spectrum illness, including schizotypal personality disorder, has added important insight into the etiology, neuropathology, and treatment of schizophrenia, which can facilitate early identification, intervention, and perhaps prevention of the illness. The heterogeneity of the schizophrenia spectrum makes its definition elusive at best. The primary aim of the Cognitive Assessment and Risk Evaluation Program at the authors' institution is to combine the current knowledge of clinical and demographic risk factors for schizophrenia with the rapidly emerging data on vulnerability markers, or endophenotypes, that are associated with schizophrenia. The use of brain-based vulnerability markers may help to identify neurobiologically and clinically meaningful subgroups within this heterogeneous population of individuals in the early stages of schizophrenia. Another important aim of the Cognitive Assessment and Risk Evaluation program is to thoroughly assess those individuals who have not converted to psychosis to understand potential protective factors, reduce the rate of false positives, and decrease disability. The current review details a strategy for researching the schizophrenia prodrome by using information gained from research in schizotypal personality disorder.