Socio-Demographic and Clinical Characteristics of the Populations Underrepresented in Mental Illness Association Studies (PUMAS) - Brazil: Descriptive Case-Control Study

Abstract

Objective: To describe the sociodemographic characteristics of the PUMAS sample in Brazil, focusing on differences between case and control groups and ethnic variation across cities.

Methods: This case-control study included a convenience sample of patients with schizophrenia and bipolar disorder, alongside matched controls, from five brazilian cities: Belém, Fortaleza, Goiânia, Salvador, and São Paulo. The Diagnostic Interview for Psychosis and Affective Disorders (DIPAD) was used to confirm diagnoses and assess lifetime psychopathology and clinical data.

Results: A total of 14,017 subjects (54.7% female, mean age 39.93 years, s.d. 12.88) were enrolled: 7,532 patients with either bipolar disorder (N=4,059) or schizophrenia spectrum disorders (N=3,473), and 6,485 controls. Over 70% self-identified as black, admixed (Pardos), or indigenous. Significant differences in self-identified skin color, according to brazilian official classifications, were observed across cities. Patients with schizophrenia showed significant socioeconomic disparities compared to those with bipolar disorders. A higher proportion of individuals with severe mental illness self-identified as admixed. Educational attainment was lower among patients, particularly those with schizophrenia.

Conclusions: This is the largest and most diverse sample in Brazil collected to investigate the genetic basis of schizophrenia and bipolar disorder. It will allow testing critical hypotheses within a socio-cultural and ethnic context underrepresented in large-scale genetic studies.

Keywords: Severe mental illness; bipolar disorder; genetic; schizophrenia.