What is depression?

Depression is a medical illness. Specifically, depression is a mood disorder that is caused by an imbalance, or unevenness, of a chemical in the brain. The term “mood” refers to an emotional state that affects how a person thinks or acts.

With depression, a person generally may feel great sadness or a loss of interest in things he or she used to enjoy. An imbalance of serotonin, a neurotransmitter (chemical) in the brain, has been linked to depression, along with other chemicals, such as norepinephrine and dopamine.

Is depression common?

About 16.2 million adult Americans suffer from what is known as major depressive disorder. The lifetime risk of women developing depression is 70 percent higher than men. Around the world, 350 million people suffer depression. Depression is responsible for the loss of $33 to $44 billion a year in the form of absenteeism, reduced productivity, and medical expenses.

Depression is also common in patients with Parkinson’s disease; an estimated 50 percent have some form of depression. Often, depression begins years before the patient has any of the physical symptoms of Parkinson’s disease (such as tremor, slowness of movement, or problems with walking and balance). This is caused by a decrease in chemicals, such as dopamine, within the brain as Parkinson’s disease begins. Depression in Parkinson’s disease affects quality of life, as much as (and sometimes more than) the movement problems themselves.

What are the types of depression?

There are several types of depression:

  • Major depression is a disabling form of depression in which a person has tremendous difficulty performing simple daily tasks. People with this type of depression are often hospitalized if the symptoms are severe and affect the person’s ability to function.
  • Dysthymia is a milder and chronic (long-term) form of depression in which patients have sadness, yet are often able to continue with their daily routine.
  • Seasonal affective disorder strikes during the winter months.
  • Postpartum depression affects women after they have given birth.
  • An adjustment disorder with depressed mood is a clear emotional reaction to a negative experience or situation, such as the loss of a loved one or being diagnosed with a severe illness.
  • Pseudo-dementia is a type of thinking or mental problem that occurs when a patient is suffering from depression that may look similar to “dementia.”
  • Organic depression is caused by chemical or physiological (physical) change in the brain from another medical condition.

What are the signs of depression?

If you have several of the following symptoms for longer than two weeks at a time, you should contact your doctor:

  • Depressed mood
  • Loss of interest or pleasure in activities
  • Sleep disturbances (unable to sleep, or sleeping for long periods of time)
  • Change in appetite
  • Excessive fatigue
  • Sudden change in level of physical activity
  • Difficulty with concentration or making decisions
  • Irritability
  • Feelings of worthlessness
  • Excessive guilt
  • Constant low self-esteem
  • Thoughts of death

There also are physical signs of depression, which include:

  • Downcast eyes
  • Slow speech
  • Flattened expressions
  • Slower movement or fatigue that may be similar to the symptoms of Parkinson’s disease

This often makes it a challenge to diagnose depression in someone with Parkinson’s disease. In addition, depression can actually make the physical effects of Parkinson’s disease worse, so it’s important to recognize and treat these symptoms right away.

Last reviewed by a Cleveland Clinic medical professional on 09/30/2015.


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