Study: Increased Risk of Parkinson Disease in Patients with Schizophrenia

A new study conducted at the University of Turku shows that patients with a schizophrenia spectrum disorder have an increased risk of Parkinson disease (PD) later in life, according to a press release. The increased risk may be due to changes in the brain’s dopamine system caused by dopamine receptor antagonists or neurobiological effects of schizophrenia.

The control study was carried out at the University of Turku in collaboration with the University of Eastern Finland, where the study examined the occurrences of previously diagnosed psychotic disorders and schizophrenia in over 25,000 Finnish patients with PD treated in 1996 to 2019.

In the study, patients with PD were noted to have previously diagnosed psychotic disorders and schizophrenia more often than the control patients of the same age not diagnosed with PD, according to the study authors.

In previous studies, several risk factors were recognized for PD, including age, male sex, exposure to insecticides, and head injuries. However, the current understanding is that the development of PD is due to a joint effect of different environment, hereditary, and patient-specific factors.

The results found that a previously diagnosed psychotic disorder or schizophrenia may be factors that increase the risk of PD later in life, according to study author and doctoral candidate Tomi Kuusimäki, University of Turku.

In PD, the neurons located in the substantia nigra in the midbrain slowly degenerate, which leads to deficiency in a neurotransmitter called dopamine. Meanwhile, for schizophrenia, the dopamine level increases in some parts of the brain.

In addition, the pharmacotherapies used in the primary treatment of PD and schizophrenia appear to have contrasting mechanisms of action. PD symptoms can be alleviated with dopamine receptor agonists, whereas schizophrenia is commonly treated with dopamine receptor antagonists.

According to Kuusimäki, the occurrence of PD and schizophrenia in the same person has been considered rare because these diseases are associated with opposite alterations in the brain’s dopamine system.

REFERENCE

Increased risk of Parkinson’s disease in patients with schizophrenia. University of Turku. https://www.utu.fi/en/news/press-release/increased-risk-of-parkinsons-disease-in-patients-with-schizophrenia. Published January 15, 2021. Accessed January 18, 2021.