Depression (also called major depressive disorder or clinical depression) is a very common mood disorder. It is usually characterized by low moods, irritability, and helplessness, but can be treated by a combination of medications and different types of therapy .
What is major depressive disorder?
Depression is a mood disorder involving feelings of sadness or hopelessness, which can have a negative impact on someone’s quality of life.
Major depressive disorder is a more severe version of depression; the symptoms are usually the same, but are usually more persistent and impactful on someone’s life. For instance, a person experiencing major depressive disorder symptoms can experience them persistently for weeks on end.
There are a vast number of symptoms of depression that you might experience, including: 
Extremely low mood, even in activities that you may usually enjoy
A constant feeling of helplessness or worthlessness throughout most of the day
Insomnia and/or Hypersomnia
Withdrawal from social situations and distancing oneself from friends and family
Thoughts of self-harm and suicide
Depression can affect anyone; however it is thought that certain factors, such as genetics, traumatic experiences, and other mental health conditions and physical disorders, can increase a person’s chance of experiencing depressive episodes.  About 8.4% of the US adult population experienced a major depressive episode in 2020 alone. 
Types of depression
Major depressive disorder is one type of depression that usually refers to more severe symptoms that last for two weeks or longer. Other types of depressive disorders include: 
Seasonal depression, also known as ‘winter depression’, when depressive symptoms are more apparent during the darker months
Bipolar disorder, which is characterized by mood swings between depressive and manic episodes
Symptoms of major depressive disorder
Symptoms of major depressive disorder affect all aspects of a person’s life, including family and social relationships, work and school, and general health.  Common symptoms can include: 
Low moods, resulting in not enjoying activities or hobbies one usually enjoys
Obsessing over feelings of guilt, helplessness, and worthlessness
Low levels of concentration and poor memory, which can affect school, work, and home life
Reduced sex drive
Thoughts of death, self-harm, and suicide
People with depression can also experience the following physical symptoms:
Inability to fall asleep, or waking very early every day no matter when one goes to sleep (Insomnia)
Feeling very tired and being unable to wake up in the morning (Hypersomnia). Insomnia and Hypersomnia can also be side effects of using antidepressants.
Changes in normal appetite, leading to undereating and weight loss or overeating and weight gain
Older people can become more forgetful and display slower movements 
Depression in different age groups
Older and younger people can experience different symptoms of depression, which can be rooted in hormonal reasons, as well as the problems and pressures people face in different stages of their life. 
Depression symptoms in adolescents and children:
Refusing to go to school and getting in trouble in school while there
More likely to experience hypersomnia and increased appetite
May develop other disorders such as a substance use disorder
Depression symptoms in adults and older adults:
More likely to suffer from insomnia and wake in the middle of the night
Older adults may experience a lack of emotion rather than the more common depressed mood. They are more likely to suffer from other health complications and mental disorders that may lead to depressive episodes.
Causes of major depressive disorder
There is currently no known exact cause of major depressive disorder. It is thought to be due to a number of factors, although there are some known risk factors that can make a person more likely to experience an episode of depression:
Genetics can play a part. It has been shown that people with relatives with depression may be more likely to have a depressive episode themselves. 
Hormonal imbalances and tolerances to hormones such as serotonin 
Substance and alcohol abuse, especially during adolescence 
Traumatic experiences in early childhood can alter brain development, leading to chemical problems in the brain
There are also some major triggers that can bring about depressive episodes, especially in those with the above risk factors:
Having another chronic or terminal disorder/condition. This is sometimes referred to as ‘secondary depression.’ 
Abuse by a parent in childhood or by a partner in adulthood
Loss of a loved one
Complications of major depressive disorder
If left untreated, major depressive disorder can lead to some serious long term complications: 
Overeating and undereating over a long period of time can cause serious weight fluctuations. Other eating-related disorders may start to develop as a result.
Other symptoms such as low mood and low sex drive may start to cause relationship problems with partners and family members.
Thoughts of death and suicide attempts. If you or anyone you know starts to have suicidal thoughts contact mental health professionals, especially in an emergency.
Diagnosing major depressive disorder
In order to be diagnosed with major depressive disorder, a doctor or psychiatrist will ask questions about a person’s mental health, physical health, family history, and drug and alcohol use. 
An individual must have displayed depressive symptoms nearly all of the time, every day for two weeks or longer, according to the DSM-5 criteria. He or she must be showing signs of low mood and a loss of pleasure in activities, as well as at least five of the following symptoms:
Persistent sadness or irritability
Changes in appetite
Loss of interest in activities
Extreme fatigue and lack of energy
Feelings of worthlessness or guilt
Thoughts of self-harm and suicide
Whilst there are no physical tests for major depression, a doctor may carry out blood tests or scans to see if there is an underlying medical condition or disorder causing the depressive episode. 
Preventing major depressive disorder
There is no guaranteed way to prevent a depressive episode. However, if a person has had a depressive episode in the past or have a family history of depression, then it is best to know the symptoms of major depressive disorder so a person can recognise them early and seek treatment. It is very important to take any medication prescribed by a doctor.
Treatment for major depressive disorder
The American Psychiatric Association recommends that people diagnosed are treated individually based on their personal needs and the symptoms they are experiencing. There are many effective treatments available upon diagnosis.
Antidepressants have been proven to be very effective in treating depressive symptoms. They usually take 6-8 weeks to show significant improvement, and doses can be tailored based on how many side effects are experienced. 
Benzodiazepines can be used alongside antidepressants if using antidepressants alone does not seem to be as effective. 
Psychotherapies such as cognitive behavioral therapy can help to learn coping methods to deal with symptoms. Interpersonal therapy can also be used to improve communication within relationships and help to recognise when to reach out for help.
Brain stimulation therapies have been shown to ease symptoms of depression in more severe cases where other forms of therapy and medications have not been as effective.
There have been studies using ketamine to ease depressive symptoms. However, there has been little evidence of it working for longer than two weeks, and it may be linked to unwanted side effects. 
Self-care for major depressive disorder
Once undergoing treatment for depression, there are some ways to help to improve one’s mood: 
Start doing activities that were once enjoyable, even if the desire is not there.
Start doing physical activity, ideally 30-minute sessions five times a week.
Try to maintain a routine. Going to bed at the same time every day and eating regular meals can decrease stress levels.
Postpone important or stressful life decisions until one feels better.
Reach out to family and friends for emotional support.
Avoid drinking alcohol or taking any recreational drugs.
American Psychiatric Association (2013). Diagnostic and statistical manual of mental disorders(5th ed.).
Department of Health and Human Services (1999). The fundamentals of mental health and mental illness. Mental Health: A Report of the Surgeon General.
Karrouri R, Hammani Z, Benjelloun R, Otheman Y. Major depressive disorder: Validated treatments and future challenges. World J Clin Cases2021; 9(31): 9350-9367
Faculty of Psychiatry of Old Age, NSW Branch, RANZCP, Kitching D, Raphael B (2001). Consensus Guidelines for Assessment and Management of Depression in the Elderly, North Sydney, New South Wales: NSW Health Department. p. 2
Clayton PJ, Lewis CE (March 1981). The significance of secondary depression. Journal of Affective Disorders. 3(1): 25–35
Dale J, Sorour E, Milner G (2008). Do psychiatrists perform appropriate physical investigations for their patients? A review of current practices in a general psychiatric inpatient and outpatient setting. Journal of Mental Health. 17(3): 293–98.
Practice guidelines for the treatment of patients with major depressive disorder (revision). The American Journal of Psychiatry. 157(4 Suppl): 1–45. April 2000. PMID 10767867.; Third edition
Ogawa Y, Takeshima N, Hayasaka Y, et al. (June 2019). Antidepressants plus benzodiazepines for adults with major depression. The Cochrane Database of Systematic Reviews. 6: CD001026.
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Published: Nov 21st 2022, Last edited: Oct 23rd 2023
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Content reviewed by a medical professional. Last reviewed: Nov 21st 2022