Schizophrenia (SCZ) and bipolar disorder (BD) are common psychiatric disorders often associated with socio-familiar burdens and life-long treatment (Charlson et al., 2018; Ferrari et al., 2016; Whiteford et al., 2013). The clinical expression of SCZ usually includes hallucinations, delusions, disorganized motor, and social withdrawal; conversely, BD comprises several disorders of emotion, energy and thought, with biphasic mood episodes of mania or hypomania and depression, expressed as recurrent episodes of behavior and cognitive symptoms (Vieta et al., 2018). The clinical picture of BD often include shifts in activity/energy, racing thoughts, concentration and episodic memory deficits, and reduced need for sleep (Charlson et al., 2018; Phillips and Kupfer, 2013). Altered functional MRI (fMRI) network disturbances have been extensively reported in both SCZ and BD (Dezhina et al., 2019; Meda et al., 2016; Öngür et al., 2010; Tamminga et al., 2014) and may disrupt the prefrontal cortex (PFC), hippocampus, medial temporal cortex (MTL), and the parahippocampal and fusiform gyrus; functional disturbances in other cerebral structures, such as the cerebellum and thalamus, were also found among SCZ subjects (Andreasen et al., 1995; Cabeza et al., 1997; Desgranges et al., 1998; Sperling et al., 2001).

Analysis of fMRI network characteristics in SCZ and BD, such as the global efficiency (GE), often show mixed results, increasing and decreasing connectivity strength (Van Dellen et al., 2020). The clinical explanations for such variability possibly comprise disease stages, medication regime, and the profile of the study population (Van Dellen et al., 2020). The relevance of ethnicity in the brain connectivity of mood and psychotic disorders remains largely unexplored, with the majority of fMRI investigations of BD and SCZ being Caucasian populations, notably from Europe, the United States, and, in the last ten years, participants of Asian origin (Fearon et al., 2006; Gong et al., 2015; Hutchinson et al., 1999), while studies are virtually inexistent in Africa and Latin America (Luna et al., 2023). Conversely, the influence of ethnicity on the incidence and psychopathological expression of SCZ and BD has been reported in community studies. One investigation in London showed higher rates of psychotic and affective disorders among African-Caribbean individuals compared to their neighborhoods of Caucasian background (Fearon et al., 2006; Gong et al., 2015; Hutchinson et al., 1999). Hallucinations and hetero aggression were more prevalent than affective symptoms in Mori group members, compared to individuals of other ethnicities in New Zealand (Tapsell and Mellsop, 2007). Thus, the characterization of GE connectivity patterns to the psychopathological expression (severity, frequency) of SCZ and BD in participants of African and indigenous backgrounds, populations with a significant presence in most Latin American countries, notably Brazil, will expand knowledge on the neurofunctional signature of such disorders across ethnic variations.

Another topic of interest is the relation between environmental exposure to psychological stress factors, such as early psychological or physical abuse, and the risk of phenotypic expression of both SCZ and BD (Sideli et al., 2012). Emotionally traumatic experiences occurring in early life stages seem to influence the clinical features of SCZ, apparently promoting a greater severity of cognitive deficits and productive symptoms, including hallucinations and delusions (Gibson et al., 2019). The biological mechanisms of traumata experiences and psychosis may include the dysregulation of the hypothalamic-pituitary-adrenal axis and dopamine system, hippocampal neuronal loss, and an increase in the amygdala volume responsible for regulating emotional responses (Morgan et al., 2020). Increased release of stress-related glucocorticoids is also associated with hippocampal atrophy, resulting in learning and memory disabilities. Childhood abuse and emotional neglect are associated with the severity of psychotic and depressive symptoms in adulthood and an overall reduction in brain volumes and increased amygdala compared to the whole brain volume (Ruby et al., 2014). Mood symptoms and anxiety also seem strongly influenced by traumatic experiences, with correlations to premorbid symptoms and comorbidities in SCZ and BD, possibly influencing the onset of such disorders (Luna et al., 2023; Trovão et al., 2022).

In our first work, we reported the sociodemographic and the neurofunctional profile of individuals with SCZ and BD of African and indigenous backgrounds using a screening questionnaire for psychiatric disorders (Luna et al., 2023). As the main results, two distinct networks' subcomponents demonstrated significantly lower GE in SCZ versus healthy controls (HC), corresponding to left posterior dorsal attention and medial left ventral attention (VA) networks. These results highlighted Default Network Mode (DNM) and salient network as relevant for the emotional processing of BD and SCZ of indigenous and black ethnicity. In the current work, we aim to investigate how connectivity GE patterns are associated with specific variables, for instance, psychotic and mood features, history of trauma in childhood and adolescence, cognitive performance, and the onset of disease.