Müller-Lyer illusion manifestation for patients with paranoid schizophrenia

Abstract

Aim of the study was to assess drugs’ effect on Müller-Lyer illusion manifestation for people with paranoid schizophrenia (PS). Methodology: PS group were patients hospitalized at Hospital of Lithuanian University of Health Sciences Kaunas Clinics Psychiatry Clinic. Control group was gathered from Dermatological and Venereal Disease Clinic. Study protocol was approved by LUHS bioethics centre. The stimuli consisted of white Müller-Lyer figures. Inner angles of figures changed from 10o to 350o. 40 figures were presented during one experiment and each patient carried out 10 experiments. Subject‘s aim was to place the central element in the exact middle between outer figures. We measured distance (arc min) between subjects’ chosen position and geometrical center of figure. Antipsychotic drug doses were converted to chlorpromazine equivalents and benzodiazepines were converted to diazepam equivalents. Drugs‘ pharmacological properties were evaluated on each experiment day individually. ANOVA and T-test were used for statistical analysis. Results: Illusion had tendency to manifest stronger for PS group, when evaluating more acute (< 79o) angles. When the figure’s inner angles approached 180o, manifestation of the illusion diminished. Results for subject group demonstrated higher standard errors of means (0.93 ± 0.02 vs. 0.79 ± 0.03) with significant difference (p < 0.01). Illusion manifested stronger when patients received higher than 300 mg of chlorpromazine equivalent dose of antipsychotics. Illusion manifestation was stronger for patients who received higher doses of benzodiazepines (> 10 mg of diazepam equivalents per day) compared to patients who received lower doses, patients who received no benzodiazepines and control group (p < 0,05). Conclusion: Müller-Lyer illusion tended to manifest stronger for patients with schizophrenia and for those who received higher doses of antipsychotics and benzod[...].