Allostatic load is associated with psychotic symptoms and decreases with antipsychotic treatment in patients with schizophrenia and first-episode psychosis.

•Allostatic load (AL) is a multisystem biomarker index and reflects physiological dysregulation.•AL is elevated in patients with psychosis relative to controls.•High AL is associated more positive symptoms and poorer functioning.•AL decreases with 6 weeks of antipsychotic treatment.•We propose that AL may be a state marker of illness severity.