Parkinson’s Disease, Depression and Dopamine

Yesterday’s revelation that the late Robin Williams had Parkinson’s disease (PD) has raised questions about links between PD and depression.

Parkinson’s disease is a complex motor-system disorder. Its underlying cause is a deterioration in parts of the brain that produce the neurotransmitter dopamine. (A neurotransmitter is a brain chemical that allows one brain cell to communicate with another.) This interferes with normal brain circuitry, resulting in PD symptoms.

The symptoms that most people identify with PD are tremor, slow movement, stooped gait and posture and a lack of facial expressiveness. However, dopamine also plays a role in the sense of smell, emotions and in the “reward circuit” that underlies many types of addiction. Often, the sense of smell is the first to suffer in those with the disorder.

Parkinson’s disease varies greatly from one person to another and each patient’s experience is unique, says the Parkinson’s Disease Foundation. The foundation estimates that up to 60 percent of Parkinson’s patients experience mild or moderate depression at some point in the disease. The organization adds that 30 percent of people with PD are diagnosed with depression before receiving a Parkinson’s diagnosis.

Depression is a medical illness that negatively affects how you feel, think and act, according to the American Psychiatric Association. Its most common symptoms include a deep feeling of sadness or a marked loss of interest or pleasure in activities. Other signs are:

  • changes in appetite that cause weight loss or gain;
  • insomnia or oversleeping;
  • loss of energy or increased fatigue;
  • restlessness or irritability;
  • feelings of worthlessness or inappropriate guilt;
  •  difficulty thinking, concentrating or making decisions; and
  • thoughts of death or suicide or attempts at suicide.

Depression and PD share many of the same symptoms, such as a sad expression, sleep disturbance, emotional upset and fatigue. This makes it difficult to identify where the one stops and another begins.

When PD and depression coexist, both should be treated because it affects quality of life. It is easy to understand how someone diagnosed with a progressive neurological disorder could become depressed and not understand that there are many treatments to ease some of the symptoms.

Do you have concerns about Parkinson’s disease? Make an appointment at the Cushing Neuroscience Institute’s Movement Disorders Center.

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