Many people feel sadness or mild depression in certain situations and circumstances. For a diagnosis of major depressive disorder to be made, a qualified health professional must:
- evaluate the symptoms and course of the illness over a period of at least two weeks
- rule out causes by other medical conditions, other psychiatric disorders, substance use, and grief in response to a significant loss
Symptoms of depression include:
- feelings of sadness, loneliness, or emptiness that last most of the day for several days on end
- loss of interest or pleasure in activities that used to be enjoyable (anhedonia)
- tiredness and chronic low energy
- difficulty thinking clearly, concentrating, making decisions or remembering
- feelings of worthlessness and guilt
- feelings of irritability, frustration or anger that are out of proportion with the circumstances
- restlessness and agitation
- sleep disturbances, including sleeping too much and sleeping too little (insomnia)
- change of appetite, most often leading to loss of weight, though some people may have increased appetite and weight gain
- Recurrent thoughts of death or suicide, as well as suicide attempts or plans
Major depression belongs to the category of mental health conditions known as mood disorders. These disorders affect a person’s mood, causing it to be consistently lower (depression and related disorders), or sometimes lower and sometimes higher (bipolar and related disorders). In children and adolescents, the mood may be irritable rather than sad.
Types of Mood Disorders
Major Depressive Disorder – what most people think of as clinical depression (see above).
Persistent Depressive Disorder (formerly “dysthymia”) – continuous long-term depression that lasts for two years or longer.
Seasonal Affective Disorder (SAD) – a period of major depression that usually occurs during winter months when days are shorter. SAD is a potential feature of major depressive disorder and is not considered a separate diagnosis.
Postpartum Depression (PPD) – an episode of major depression that occurs in some women following childbirth. About half of all cases of PPD actually begin before childbirth. Like SAD, PPD is a feature of major depressive disorder.
Bipolar Disorder (formerly “manic depression”) – a serious disorder involving major mood swings that include emotional highs (mania or hypomania) and lows (depression). Although people diagnosed with bipolar disorder may at times experience severe depression, the treatment for bipolar is very different from that for major depressive disorder.
“Situational” Depression – not a formal diagnosis, feature or disorder, but commonly used to describe the depressed mood or sadness many people feel when dealing with a stressful life event, such as a death in the family, divorce, or sudden unemployment.
Depression and depression-like symptoms can also be caused by or linked to substance use or withdrawal, menstruation in women, use of some medications, or the physical effects of a medical condition.
Major depression and related disorders are frequently seen with other mental health conditions, known as co-occurring disorders. The most frequent are: anxiety disorders, substance use disorders, eating disorders and medical illnesses such as cancer, diabetes and Alzheimer’s syndrome.