Browsing by Subject "schizophrenia"
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Item An Analysis of the Two-Hit Model of Schizophrenia(The Undergraduate Research Journal of Psychology at UCLA, 2016-03) Fleischman, Rivka; Wilson, Camille; Schiffman, JasonThe two-hit model, which can be used to describe the causal pathway of schizophrenia, has many strengths and limitations. Although the model can help explain the origins of schizophrenia and may account for the complexity of the disorder, its weaknesses include an inability to effectively describe the heterogeneity of the disorder, non-specificity to schizophrenia, a non-falsifiable approach to assimilating individual differences, challenges in knowing where each risk factor falls in the model, and difficulties ascribing causality and direction of effects. Despite its limitations, this model has many clinical implications for the early identification of schizophrenia. However, given the limitations of the model, it may be difficult to use the model in early intervention effortsItem Fixed-time schedule effects in combination with response-dependent schedules(Wiley Online Library, 2011-03) Borrero, John C.; Bartels-Meints, Jaime A.; Sy, Jolene R.; Francisco, Monica T.We evaluated the effects of fixed-interval (FI), fixed-time (FT), and conjoint (combined) FI FT reinforcement schedules on the responding of 3 adults who had been diagnosed with schizophrenia. Responding on vocational tasks decreased for 2 of 3 participants under FT alone relative to FI alone. Responding under FI FT resulted in response persistence for 2 of 3 participants. Results have implications for the maintenance of desirable behavior, as well as for situations in which FT treatment has been implemented for problem behavior and problem behavior is nevertheless reinforced by caregivers.Item Minor Physical Anomalies, Dermatoglyphic Asymmetries, and Cortisol Levels in Adolescents With Schizotypal Personality Disorder(American Psychiatric Association, 1999-04-01) Weinstein, Dana Davis; Diforio, Donald; Schiffman, Jason; Walker, Elaine; Bonsall, RobertA relationship between schizotypal personality disorder and schizophrenia has been documented in behavioral genetic studies, and there are similarities in the cognitive deficits and brain abnormalities associated with these disorders. Adolescents with schizotypal personality disorder are of particular interest because the postpubertal period is a critical one for the development of a DSM axis I disorder. It is likely that some schizotypal adolescents will remain stable over time, some will improve, and a subgroup will develop schizophrenia. This study tested the hypotheses that, like schizophrenic patients, schizotypal adolescents manifest an elevated rate of minor physical and dermatoglyphic anomalies, both of which suggest prenatal neurodevelopmental abnormalities. Cortisol release is also of interest because of evidence that the hypothalamic-pituitary-adrenal axis may influence the behavioral expression of vulnerability to schizophrenia. METHOD: Minor physical anomalies, dermatoglyphic asymmetries, and salivary cortisol levels were measured in three groups of adolescents: 20 with schizotypal personality disorder, 20 with other personality disorders, and 26 with no disorder. Assessments began at noon, and four saliva samples were obtained at hourly intervals. RESULTS: The schizotypal personality disorder group showed more minor physical anomalies and dermatoglyphic asymmetries than the normal comparison group and higher cortisol levels than both of the other groups. Group differences in cortisol level were most pronounced at the beginning of the evaluation. Cortisol level and age were positively correlated. CONCLUSIONS: The findings support the assumption that schizotypal personality disorder is associated with perturbations in fetal neurodevelopment and, under some circumstances, a heightened cortisol response.Item Toxoplasma gondii as a Risk Factor for Schizophrenia and Psychosis(2016-01-01) Epstein, Gregory B.; Schiffman, Jason; Pitts, Steven; Psychology; PsychologyToxoplasma gondii is a parasitic protozoan found in nearly one-third of the population worldwide. Although most individuals with a latent Toxoplasma gondii infection are asymptomatic, several studies have linked infection with the parasite to several forms of psychopathology, including anxiety, personality disorders, bipolar disorder, schizophrenia, and suicidality. Other studies have established that individuals with schizophrenia are at nearly three times greater odds of being infected with Toxoplasma gondii than individuals without schizophrenia. Only recently has research begun to understand the common etiology of Toxoplasma gondii infection and schizophrenia, as well as other psychotic disorders. The current study examined the prevalence of Toxoplasma gondii in an urban, help-seeking sample of adolescents and young adults with varying levels of risk for psychosis, as well as a range of psychosis-risk diagnoses. The prevalence of Toxoplasma gondii infection in this sample was lower than expected and neither schizophrenia-risk nor psychosis-risk showed a significant relation with Toxoplasma gondii. Explanations for the low prevalence of Toxoplasma gondii in this sample were explored.