Depression (Major Depressive Disorder)

Ethan Cullen
Author: Ethan Cullen Medical Reviewer: Amy Shelby Last updated:

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 [1].

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: [2]

  • 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. [3] About 8.4% of the US adult population experienced a major depressive episode in 2020 alone. [12]

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: [1]

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. [1] Common symptoms can include: [2]

  • 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
  • High irritability
  • 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 [5]

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. [1]

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
  • Decreased libido
  • 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. [3]
  • Hormonal imbalances and tolerances to hormones such as serotonin [6]
  • Substance and alcohol abuse, especially during adolescence [2]
  • 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.’ [7]
  • 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: [2]

  • 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.
  • Inability to return to work or school for a long period of time. This can cause additional stress if it leads to financial issues.
  • 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. [1]

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
  • Sleep problems
  • Loss of interest in activities
  • Restlessness
  • Extreme fatigue and lack of energy
  • Feelings of worthlessness or guilt
  • Difficulty concentrating
  • 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. [8]

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. [9]
  • Benzodiazepines can be used alongside antidepressants if using antidepressants alone does not seem to be as effective. [10]


  • 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.[1]
  • 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.[1]

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. [11]

Self-care for major depressive disorder

Once undergoing treatment for depression, there are some ways to help to improve one’s mood: [1]

  • 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.

Helping someone with major depressive disorder

The best way to help someone showing depressive symptoms is to help them contact a medical professional so they can start treatment. However, there are still other ways to help: [1]

  • Invite them to activities or social events that they used to enjoy. Make sure they still know that they are welcome regardless of their symptoms.
  • Make their treatment process as easy as possible, such as setting reminders for their medication or giving them a lift to a therapy session.
  • Most importantly, ask what they need. A friendly supportive face may make them more likely to keep on track with treatment.
  1. Depression. (n.d.). National Institute of Mental Health (NIMH).
  2. American Psychiatric Association (2013). Diagnostic and statistical manual of mental disorders(5th ed.).
  3. Department of Health and Human Services (1999). The fundamentals of mental health and mental illness. Mental Health: A Report of the Surgeon General.
  4. Karrouri R, Hammani Z, Benjelloun R, Otheman Y. Major depressive disorder: Validated treatments and future challenges. World J Clin Cases2021; 9(31): 9350-9367
  5. 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
  6. Bains N, Abdijadid S. Major Depressive Disorder. [Updated 2022 Jun 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from:
  7. Clayton PJ, Lewis CE (March 1981). The significance of secondary depression. Journal of Affective Disorders. 3(1): 25–35
  8. 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.
  9. 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
  10. 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.
  11. Corriger, A., & Pickering, G. (2019). Ketamine and depression: a narrative review. Drug Design, Development and Therapy, Volume 13, 3051–3067.
  12. National Alliance on Mental Illness. (n.d.). Depression. NAMI. Retrieved October 17, 2022, from
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Ethan Cullen
Author Ethan Cullen Writer

Ethan Cullen is a medical writer with a Bachelor of Arts degree in Philosophy, Politics, and Economics from Oxford University.

Published: Nov 20th 2022, Last edited: Oct 23rd 2023

Amy Shelby
Medical Reviewer Amy Shelby M.S. Counseling Psychology

Amy Shelby is a medical reviewer with a B.A. in Psychology from Northwestern and an M.S. in Psychology from Chatham University.

Content reviewed by a medical professional. Last reviewed: Nov 21st 2022