A recent study concludes that schizophrenia spectrum disorders increase the risk of developing Parkinson’s disease.The study included data from more than 3,000 people with Parkinson’s.
This finding is surprising, because the conditions have opposite effects on the brain.
Despite the two conditions having opposite effects on the brain’s dopamine system, a new study suggests that people with schizophrenia are more likely to develop Parkinson’s in later life.
Parkinson’s disease is a neurodegenerative disorder in which the brain cells responsible for producing dopamine progressively die.The resulting lack of dopamine causes symptoms such as tremor, rigidity, extremely slow movements, and impaired balance.
The National Institutes of Health estimate that every year around 50,000 people in the United States receive a Parkinson’s diagnosis.
Currently, about half a million people are living with the disease in the U.S. — a number that is likely to increase as the population ages, because Parkinson’s is more common among older adults.
By contrast, schizophrenia spectrum disorders — a range of conditions characterized by psychosis — tend to develop in young adulthood and are thought to be caused by an overactive dopamine system in the brain.
So whereas Parkinson’s can be treated with a drug called levodopa, which boosts dopamine levels, schizophrenia is often treated with drugs that block the activity of dopamine.
The opposite effects of these two illnesses on the dopamine system have given rise to the long-standing belief that people with schizophrenia are much less likely to develop Parkinson’s later in life.
A large retrospective study by researchers at the University of Turku in Finland and the University of Eastern Finland in Kuopio casts serious doubt on this belief.“The occurrence of Parkinson’s disease and schizophrenia in the same person has been considered rare because these diseases are associated with opposite alterations in the brain’s dopamine system,” says doctoral candidate Tomi Kuusimäki from the University of Turku, who led the research. “Our study changes this prevailing conception.”
The researchers analyzed the medical records of 3,045 people with Parkinson’s treated between 2004 and 2019 in southwestern Finland, and 22,189 patients entered in a Finnish national register between 1996 and 2015.