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Objective: Extensive investigations have been conducted into predictors of schizophrenia outcome. The heterogeneity of the illness implies that many factors should be taken into account. Some studies have reported the relationship between increased β-endorphin concentration and predominant negative symptoms. Methods: We included 77 outpatients with schizophrenia and 74 healthy controls. Data referring to duration and course of illness, hospitalization number and treatment were collected on the basis of clinical interviews and medical documentation analysis. The β-endorphin concentrations were assessed once in all participants, at the onset of the study. Results: A chronic course of illness was found in 44 of the 77 schizophrenics. Patients with schizophrenia, especially those with a chronic course of illness, revealed significantly higher β-endorphin concentrations than those with an episodic course and controls (mean 29.70 vs 19.86 pmol/L; p=0.0001). Increased levels of β-endorphin were related to longer duration of illness (R=0.294, p=0.009) and frequent psychiatric hospitalization (R=0.346, p=–0.002). Conclusion: Endorphins may be potential biological predictors of persistent negative symptoms and final outcome in schizophrenia.
Urban-Kowalczyk, M., Kotlicka-Antczak, M., Ewa Rudecka, D. S., & Śmigielski, J. (2019). The relationship between course of illness and β-endorphin plasma levels in patients with schizophrenia. Neuropsychiatric Disease and Treatment, 15, 3609–3614. https://doi.org/10.2147/NDT.S225321