Parkinson's Disease: Causes, Symptoms & Stages

Instructor: Gary Gilles

Gary has a Master's degree in Counseling Psychology and has been teaching and developing courses in higher education since 1988.

Parkinson's disease is a progressive condition that affects bodily movement and results from an essential brain chemical that gradually diminishes in some people. Learn more about Parkinson's disease as well as its symptoms and progression.

About Parkinson's Disease

Parkinson's disease is a chronic disorder of the nervous system that affects movement. The exact cause of Parkinson's disease is still unclear, but it appears to result when nerve cells in the brain (neurons) begin to die. These neurons naturally produce a vital chemical called dopamine. We need ample amounts of dopamine for bodily movement and coordination. When too many of these neurons die, the amount of dopamine in our system decreases, which makes movement such as walking or balance increasingly difficult. Parkinson's disease is progressive, meaning that movement difficulties worsen over time.

Suspected Causes


Some research has pointed toward a genetic link as a possible cause in certain people. But, the evidence is not strong. Most people with Parkinson's disease do not have a genetic abnormality. So, while there may be an inherited component for some people with Parkinson's, it does not adequately explain the majority of cases.

Environmental Triggers

There is also some evidence that exposure to certain toxins in the environment might destroy the neurons that produce dopamine. Questionable toxins include carbon monoxide (such as pollution from cars and trucks) and select chemicals used in manufacturing and pesticides. But again, these are suspected causes of Parkinson's. More research is needed before clearer associations can be made.


The symptoms of Parkinson's disease vary from person to person but are usually mild in the early stages, perhaps even unnoticed by most people. As the disease progresses, symptoms become more evident and difficult to manage.

Early Stage Parkinson's Disease

In the early stage of Parkinson's disease, the symptoms may only be observed on one side of the body. These symptoms include:

  • Tremors: a tremor is a classic symptom of Parkinson's. A tremor is a slight trembling of the hand or fingers or a back-and-forth rubbing of the thumb and forefinger (called a pill-rolling tremor) when the hand or arm is at rest.
  • Posture and balance: the person with early stage Parkinson's may show noticeably poor posture or balance problems when walking.

Stooped posture common with Parkinson

Stage Two

In the second stage of Parkinson's disease, the symptoms of tremor and balance problems extend to both sides of the body. Family members begin to see their loved one struggle with routine physical tasks, such dressing or climbing stairs.

Stage Three

In stage three, the progression of the disease begins to noticeably slow physical movement and limit mobility. It may inhibit the person's ability to walk straight, stand or eat without assistance. When a loved one reaches stage three of Parkinson's, it is no longer safe for them to live alone. They may need assistance with many daily activities.

Stage Four

Symptoms in stage four are typically severe. Stiffness and rigidity of the legs and arms is common. This may make walking difficult or prompt what is commonly referred to as freezing episodes. A freezing episode occurs when the person with Parkinson's literally stops walking or appears to freeze between steps. This occurs because the progressive stiffness and rigidity settling in to the legs creates the sensation that their feet are stuck to the ground when attempting to move.

To unlock this lesson you must be a Member.
Create your account

Register to view this lesson

Are you a student or a teacher?

Unlock Your Education

See for yourself why 30 million people use

Become a member and start learning now.
Become a Member  Back
What teachers are saying about
Try it risk-free for 30 days

Earning College Credit

Did you know… We have over 200 college courses that prepare you to earn credit by exam that is accepted by over 1,500 colleges and universities. You can test out of the first two years of college and save thousands off your degree. Anyone can earn credit-by-exam regardless of age or education level.

To learn more, visit our Earning Credit Page

Transferring credit to the school of your choice

Not sure what college you want to attend yet? has thousands of articles about every imaginable degree, area of study and career path that can help you find the school that's right for you.

Create an account to start this course today
Try it risk-free for 30 days!
Create an account