Patients with schizophrenia have increased risk of Parkinson's disease, shows study A new study conducted at the University of Turku, Finland, shows that patients with a schizophrenia spectrum disorder have an increased risk of Parkinson's disease later in life. The increased risk may be due to alterations in the brain's dopamine system caused by dopamine receptor antagonists or neurobiological effects of schizophrenia. The record-based case-control study was carried out at the University of Turku in collaboration with the University of Eastern Finland. The study examined the occurrences of previously diagnosed psychotic disorders and schizophrenia in over 25,000 Finnish Parkinson's disease (PD) patients treated in 1996-2019.