What Is Depression

Definition of Depression

Depression is a serious medical illness that will affect 1 out of 6 people at some point in their life. Depression impairs a person’s ability to function as they normally would, such as decreased social activity, decreased productivity at work or school. Along with depressed mood, individuals most commonly experience decreased motivation and interest in doing things they previously enjoyed or could perform with less effort. Depression commonly interferes with sleep and appetite. If untreated, it may lead to feelings of hopelessness, helplessness or worthlessness. Ultimately, depression is a disabling brain disease that can interfere with all aspects of life, and contribute to other medical and psychiatric problems.

Major Types of Depression

Three types of depressive disorders are most common:

  • Major Depressive Disorder (MDD) can range in severity and may include some or all of the following symptoms for at least 2 consecutive weeks: sadness, loss of interest, motivation or pleasure along with decreased energy, changes in appetite, sleep or concentration, thoughts of death or suicide, physical slowing or restlessness, and feelings of worthlessness or guilt. Such a disabling episode may happen only once in a lifetime, but more commonly it occurs more than once.
  • Persistent Depressive Disorder (previously called ‘Dysthymia’) is a less acutely disabling form of depression that afflicts a person most of the time for at least 2 years. An episode of MDD may occur before, during or after persistent depressive disorder. It affects about 10 times less people than MDD.
  • Bipolar Disorder, known informally as ‘manic-depressive’ illness, may have the same symptoms and experiences as someone with MDD, but at least once in their life have experienced a ‘manic’ episode. A manic episode may be described as the “opposite” of depression, in that a person has symptoms of high energy and activity. Motivation also tends to be high, although people are often easily distracted, and so productivity may not be better. Energy is usually markedly increased with less need for sleep. Notably, there is often some change in personality that may be noticed by others as impulsive, grandiose (inflated sense of one’s abilities or position), or talkative. There is usually a ‘crash’ afterwards with severe depressive symptoms, and commonly individuals make detrimental decisions in this state.

What Causes Depression?

Like many medical illness like high blood pressure, cardiovascular disease, or cancer, depression results from both inherited and environmental causes. Depression often runs in families, and an identical twin has a 70% chance of having depression if their counterpart has depression. Environmental factors like exposure to abuse, neglect or other extreme stressors also increase the likelihood for depression, and single life episodes may trigger a depressive episode. Some people suffer from low self-esteem, are easily overwhelmed, or have other personality traits that can increase the likelihood for depression. Whether genetic, or environmental, both cause changes in brain cells at the level of DNA and protein production that disrupt normal brain function. Treatments can reverse these changes.