Browsing by Author "Ramírez-Mahaluf, Juan Pablo"
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Publication Quantitative Susceptibility Mapping MRI in Deep-Brain Nuclei in First-Episode Psychosis(2023) García Saborit, Marisleydis; Jara, Alejandro; Muñoz, Néstor; Milovic, Carlos; Tepper, Angeles; Alliende, Luz María; Mena, Carlos; Iruretagoyena, Bárbara; Ramírez-Mahaluf, Juan Pablo; Díaz, Camila; Nachar, Ruben; Castañeda, Carmen Paz; González, Alfonso; Undurraga, Juan; Crossley, Nicolás; Tejos, CristianBackground: Psychosis is related to neurochemical changes in deep-brain nuclei, particularly suggesting dopamine dysfunctions. We used an magnetic resonance imaging-based technique called quantitative susceptibility mapping (QSM) to study these regions in psychosis. QSM quantifies magnetic susceptibility in the brain, which is associated with iron concentrations. Since iron is a cofactor in dopamine pathways and co-localizes with inhibitory neurons, differences in QSM could reflect changes in these processes. Methods: We scanned 83 patients with first-episode psychosis and 64 healthy subjects. We reassessed 22 patients and 21 control subjects after 3 months. Mean susceptibility was measured in 6 deep-brain nuclei. Using linear mixed models, we analyzed the effect of case-control differences, region, age, gender, volume, framewise displacement (FD), treatment duration, dose, laterality, session, and psychotic symptoms on QSM. Results: Patients showed a significant susceptibility reduction in the putamen and globus pallidus externa (GPe). Patients also showed a significant R2* reduction in GPe. Age, gender, FD, session, group, and region are significant predictor variables for QSM. Dose, treatment duration, and volume were not predictor variables of QSM. Conclusions: Reduction in QSM and R2* suggests a decreased iron concentration in the GPe of patients. Susceptibility reduction in putamen cannot be associated with iron changes. Since changes observed in putamen and GPe were not associated with symptoms, dose, and treatment duration, we hypothesize that susceptibility may be a trait marker rather than a state marker, but this must be verified with long-term studies.Item Uso de cannabis en jóvenes hospitalizados por un primer episodio de psicosis: un estudio caso-control(2020) Castañeda, Carmen Paz; Iruretagoyena, Bárbara; Nachar, Rubén; Mancilla, Felipe; Díaz, Camila; Gallardo, Carlos; Mena, Cristián; Ramírez-Mahaluf, Juan Pablo; Undurraga, Juan; González-Valderrama, Alfonso; Crossley, Nicolás A.Background: Cannabis use among young people in Chile has increased significantly in the last years. There is a consistent link between cannabis and psychosis. Aim: To compare cannabis use in patients with a first episode of psychosis and healthy controls. Material and Methods: We included 74 patients aged 20 ± 3 years (78% males) admitted to hospital with a first episode of psychosis and a group of 60 healthy controls aged 23 ± 4 years (63% males). Cannabis consumption was assessed, including age of first time use and length of regular use. Results: Patients with psychosis reported a non-significantly higher frequency of life-time cannabis use. Patients had longer periods of regular cannabis use compared with healthy subjects (Odds ratio [OR] 2.4; 95% confi-dence intervals [CI] 1.14-5.05). Patients also used cannabis for the first time at an earlier age (16 compared with 17 years, p < 0.0). The population attributable fraction for regular cannabis use associated with hospital admissions due to psychosis was 17.7% (95% CI 1.2-45.5%). Conclusions: Cannabis use is related to psychosis in this Chilean group of patients. This relationship is stronger in patients with early exposure to the drug and longer the regular use. One of every five admissions due to psychosis is associated with cannabis consumption. These data should influence cannabis legisla-tion and the public policies currently being discussed in Chile.