Parkinson’s disease is a neurodegenerative disorder in which nerve cells in a part of the brain called the substantia nigra don’t produce enough of the neurotransmitter dopamine, according to the Parkinson’s Foundation. Not having enough dopamine is what causes the movement symptoms that distinguish Parkinson’s disease, including tremors, limb rigidity, and gait problems.
Although it is a movement disorder, Parkinson’s disease can bring about non-movement symptoms that include cognitive impairment, depression, sleep disorders, and constipation, according to the Parkinson’s Foundation.
Parkinson’s disease is a progressive disorder. This means the disease gets worse over time. Although Parkinson’s disease is incurable, its symptoms are treatable. Data from some clinical research trials suggest that there is hope to slow  Parkinson’s disease progression through early intervention, although there’s not enough data to “conclusively demonstrate” that this is possible, according to The American Journal of Managed Care.