The relation of formal thought disorder with social cognition and their effects on social functioning in schizophrenia patients and first degree relatives

Formal thought disorder (FTD) is considered to be one of the core symptoms of schizophrenia and is a possible risk indicator for the disorder as they are seen in milder forms in first-degree relatives of patients. Social cognition deficits in schizophrenia have been shown in many studies and its relation with other symptoms such as FTD is an important area of research. This study aims to determine FTD and social cognition deficits including theory of mind (ToM), emotion recognition and social knowledge in schizophrenia patients and their first degree relatives (siblings), to examine the relation between FTD and social cognition domains, and to examine the effects of FTD and social cognition skills on social functioning and quality of life in patients. To conduct the validity and reliability study of the Turkish version of the Situational Features Recognition Test-2 (SFRT-2), which has been developed to assess social knowledge, was additionally aimed. Participants consisted of N=100 patients diagnosed with schizophrenia according to DSM-5, N=41 first-degree relatives (siblings) of schizophrenia patients without psychiatric disorders, and N=60 healthy controls. The sociodemographic characteristics of all participants were noted in detail, as well as the clinical information of schizophrenia patients. All participants were administered the Turkish version of Thought and Language Disorder Scale (TALD), the Reading the Mind in the Eyes Test, the Hinting Task, the Facial Emotion Identification Test, the Facial Emotion Discrimination Test and the Situational Features Recognition Test-2 as social cognition tests, the Digit Span Test, the Verbal Fluency Test and the Auditory Consonant Trigram Test (ACT) for neurocognitive assessment, and the Personal and Social Performance Scale (PSP) to assess social functioning. Additionally, in schizophrenia patients, the Positive and Negative Syndrome Scale (PANSS) and the Clinical Global Impression Scale (CGI) were administered to determine the severity of illness, and the Quality of Life Scale was administered to assess quality of life. The results of the study revealed that schizophrenia patients had higher scores in all domains of TALD and significant impairments in all social cognition tests compared to controls, while siblings group had only more positive FTD than controls, and did not differ from controls in terms of social cognition skills. In schizophrenia patients, negative FTD was negatively correlated with ToM and emotion recognition among social cognition domains, whereas in healthy controls, the presence of symptoms related to negative FTD was negatively correlated with ToM and social knowledge performance. In schizophrenia patients, negative FTD was found to be associated with lower social functioning and deterioration in quality of life, whereas ToM skills were found to be associated with an increase in quality of life. In schizophrenia patients, social functioning and quality of life were best predicted by negative FTD and social knowledge performance, whereas in healthy controls, social functioning was best predicted by symptoms related to negative FTD and ToM skills. In addition, in the test-retest reliability analysis of the Situational Features Recognition Test-2 (SFRT-2), the correlation between the pre- and post-test of the scale was found to be high and significant. In the concurrent validity, SFRT-2 scores were found to be correlated with other social cognition tests. Receiver Operating Characteristic (ROC) analysis for discriminant validity showed that the test showed good discrimination between schizophrenia patients and healthy controls (AUC = 0.74). In conclusion, the Turkish version of the SFRT-2 was shown to provide a reliable and valid measure to assess social knowledge deficit in patients with schizophrenia. The results of this study suggest that among FTD in schizophrenia patients, mainly negative FTD is associated with social cognition deficits, and negative FTD and social knowledge performance have substantial effects on social functioning and quality of life of schizophrenia patients. It is important to better understand negative FTD and negative symptoms in general and social cognition deficits in schizophrenia patients and to prioritize the development of treatment approaches targeting these areas in order to improve the social functioning and quality of life of patients.