Clinical depression (also called major depressive disorder or unipolar depression) is a state of intense sadness, anhedonia (the absence of pleasure or the ability to experience it) or despair that has advanced to the point of being disruptive to an individual's social functioning and/or activities of daily living.

Although a low mood or state of dejection that does not affect functioning is often colloquially referred to as depression, clinical depression is a clinical diagnosis and may be different from the everyday meaning of "being depressed". Many people identify the feeling of being depressed as "feeling sad for no reason", or "having no motivation to do anything". One suffering from depression may feel tired, sad, irritable, lazy, unmotivated, and apathetic. Clinical depression is generally acknowledged to be more serious than normal depressed feelings. It often leads to constant negative thinking and escapism through substance abuse.

Clinical depression or Major Depressive Disorder (MDD) is diagnosed when an individual experiences a severely depressed mood that includes five or more primary clinical depression symptoms that cause an impairment in usual functioning nearly every day, during the same two-week period.

Major Depressive Disorder is specified as either "a single episode" or "recurrent"; periods of depression may occur as discrete events or as recurrent over the life span. Episodes of major or clinical depression may be further divided into mild, major or severe. Where the patient has already had an episode of mania or markedly elevated mood, a diagnosis of bipolar disorder is usually made instead of MDD; depression without periods of elation or mania is therefore sometimes referred to as unipolar depression because their mood remains on one pole. The diagnosis also usually excludes cases where the symptoms are a normal result of bereavement.

Primary Symptoms

Feelings of overwhelming sadness and/or fear, or the seeming inability to feel emotion (emptiness).
A decrease in the amount of interest or pleasure in all, or almost all, daily activities.
Changing appetite and marked weight gain or loss.
Disturbed sleep patterns, such as insomnia, loss of REM sleep, or excessive sleep (Hypersomnia).
Psychomotor agitation or retardation nearly every day.
Fatigue, mental or physical, also loss of energy.
Intense feelings of guilt, helplessness, hopelessness, worthlessness, isolation/loneliness
and/or anxiety.
Feeling and/or fear of being abandoned by those close to one.
Trouble concentrating, keeping focus or making decisions or a generalized slowing and obtunding
of cognition, including memory.
Recurrent thoughts of death (not just fear of dying), desire to just "lay down and die" or
"stop breathing", recurrent suicidal ideation without a specific plan, or a suicide attempt or
a specific plan for committing suicide.

Secondary Symptoms - Often reported but not usually taken into account in diagnosis include:

Self-loathing.
A decrease in self-esteem.
Inattention to personal hygiene.
Sensitivity to noise.
Physical aches and pains, and the belief these may be signs of serious illness.
Fear of 'going mad'.
Change in perception of time.
Periods of sobbing.
Possible behavioral changes, such as aggression and/or irritability.

 

Clinical depression affects about 16% of the population on at least one occasion in their lives. In some countries, such as Australia, one in four women and one in eight men will suffer from depression. The mean age of onset, from a number of studies, is in the late 20s. About twice as many females as males report or receive treatment for clinical depression, though this imbalance is shrinking over the course of recent history; this difference seems to completely disappear after the age of 50 - 55, when most females have passed the end of menopause.

It should be noted that these numbers are only for those who report or receive treatment for depression; men are less likely to report feeling depressed, and also less likely to seek treatment, possibly due to gender roles. Clinical depression is currently the leading cause of disability in North America as well as other countries, and is expected to become the second leading cause of disability worldwide (after heart disease) by the year 2020, according to the World Health Organization.

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