Sadness, feeling down, having a loss of interest or pleasure in daily activities - these are symptoms of depression familiar to all of us.
Having these problems persistently, such that they affect life for a period of time, could signal the treatable condition of depression, rather than a passing episode of "feeling down" - which most of us feel at some point.
According to the US Centers for Disease Prevention and Control (CDC), 8% of people over the age of 12 years has depression in any two-week period.1
The World Health Organization (WHO) puts depression at the top of the list - it is the most common illness worldwide and the leading cause of disability. The organization estimates that 350 million people around the world are affected by depression.2
Depression is more common among women than men.2
Contents of this article:
You will also see introductions at the end of some sections to any recent developments that have been covered by MNT's news stories. Also look out for links to information about related conditions.
Fast facts on depression
Here are some key points about depression. More detail and supporting information is in the body of this article.
- Depression is a mood disorder. The low mood involves sadness and loss of interest that persists beyond the temporary feelings we all have occasionally and is severe enough to interfere with daily life.
- Worldwide, 350 million people are estimated to have depression and the condition is more common among women than men.
- Life events such as bereavement produce mood changes that can usually be distinguished from the features of depression.
- Separate diagnoses include bipolar disorder, psychotic depression, postpartum depression and seasonal affective disorder.
- The causes of depression are not fully understood but are likely to be a complex combination of genetic, biological, environmental and psychosocial factors.
- In addition to the mental symptoms, such as inappropriate feelings of guilt, physical ones may include problems with sleep and a loss of energy.
- Diagnosis is usually made by a doctor conducting a structured interview to ask specific questions to rate levels of depression, if present.
- Treatments include psychological treatments, including cognitive behavioral therapy and interpersonal psychotherapy, and drug therapies, including a range of antidepressant classes.
- Whether drug or talking therapies, or both, are the most appropriate treatment depends on the individual, and they are similar in efficacy.
What is depression?
Depression is a mental health disorder, a psychiatric condition. Specifically, it is a mood disorder characterized by persistently low mood in which there is a feeling of sadness and loss of interest.3,4
Depression is known by different medical terms, some of which signify a particular diagnosis:4-6
Depression can affect appetite.
- Clinical depression
- Major depression
- Major depressive disorder
- Persistent depressive disorder
- Dysphoric disorder.
Depression is a persistent problem, not a passing one - the average length of a depressive episode is 6 to 8 months.3
Depression is different from the fluctuations in mood that we all experience as a part of a normal and healthy life. Temporary emotional responses to the challenges of everyday life do not constitute depression.3
Likewise, even the feeling of grief resulting from the death of someone close or other kind of loss is not itself depression if it does not persist.5 Depression can, however, be related to bereavement - when depression follows a loss, psychologists call it a "complicated bereavement."7
Similarly, discouraged mood that results from the disappointment of a life event such as a financial problem, a serious illness, or even involvement in a natural disaster, does not necessarily mean depression.5
Unipolar versus bipolar depression
A separate condition may be diagnosed if it is characterized by both manic and depressive episodes separated by periods of normal mood, in which case the mood disorder is not depression but bipolar disorder, which used to be known as manic depression or manic-depressive illness.2
Unipolar or major depressive disorder is estimated to be 3.5 times more prevalent than bipolar spectrum disorders.8
Unipolar depression may be described as mild, moderate, or severe, and can involve anxiety and other symptoms - but no manic episodes. However, nearly 40% of the time over a 13-year period, individuals with bipolar disorder are depressed, making the two conditions difficult, and important, to distinguish.8
Depression brought on by the birth of a baby is a separate diagnosis.
Depression brought on by the birth of a baby is a separate diagnosis.
This diagnosis is characterized by depression accompanied by psychosis.6
Psychosis can involve delusions - false beliefs and detachment from reality - or hallucinations - sensing things that do not exist.
Women often experience the "baby blues" with a newborn, but postpartum depression - also known as postnatal depression - is more severe and estimated to affect about 1 in 10 women who have given birth.6
Seasonal affective disorder
Often abbreviated to SAD, seasonal affective disorder is related to the reduced daylight of winter - the depression occurs during this season but lifts for the rest of the year and in response to light therapy.6
Countries with long or severe winters seem to be affected more by SAD.5
Causes of depression
The causes of depression are not fully understood and may not be down to a single source. Depression is likely to be caused by a complex combination of factors:3,5,6,9
- Biological - with changes in noradrenergic, dopaminergic and serotonergic neurotransmitter levels theorized
- Psychological and social/psychosocial.
Some people are at higher risk of depression than others - risk factors, which play into the above causes, include:3,5,6,9
- Life events - for example, unemployment, divorce, poverty, although these events lead to lasting, severe depression usually only in people predisposed to it
- Personality. Failure of adaptive mechanisms/coping strategies to stressors
- Genetic factors. First-degree relatives of depressed patients are themselves at higher risk, and occurrence of depression between identical twins is high. Genetic factors may influence individual responses to events that trigger depression
- Childhood trauma can cause long-term brain changes affecting responses to fear and stress. Other history also raises the risk, including a suicide attempt, or any form of abuse - sexual, physical or substance
- Some prescription drugs - including corticosteroids, some beta-blockers, interferon, and reserpine - can lead to depression.
- Abuse of recreational drugs - including alcohol, amphetamines - can accompany depression or result in it. There is a high level of comorbidity between drug abuse and depression
- A past head injury
- Past diagnosis of depression - people who have had an episode of major depression are at higher risk of a subsequent one
- Chronic pain syndromes in particular, but also other chronic conditions, such as diabetes, chronic obstructive pulmonary disease, cardiovascular disease.
On the next page we look at the symptoms of depression and how it is diagnosed. On the final page we discuss the treatments available to those suffering with depression.