Diseases & Conditions


Major Depressive Disorder

Diseases & Conditions


What is major depression?

Depression is a mood disorder that goes beyond everyday sadness. It causes profound sadness that interferes with the patient’s daily life disrupting the ability to perform normal tasks. Depression ranges in seriousness from mild, temporary episodes of sadness to severe, persistent depression. Clinical depression is the more severe form, also known as major depression or major depressive disorder.

Depression is the most common psychiatric disorder worldwide affecting 350 million people.1


What causes depression?

The exact causes of depression are still unknown. A combination of biological, environmental, genetic and psychological factors can contribute to the development of this mental disorder:2

  • Biological differences: Images of the brain have shown that parts of the brain involved in mood and behavior appear to be different in patients with depression compared to people without depression.
  • Brain chemistry: Some changes involving neurotransmitters in the brain involved in maintaining mood stability may play a role in depression.
  • Genetic: Some types of depression tend to run in families. Certain genes appear to be the culprit in making some people more prone to develop depression.
  • Psychological factors: Losing a person we love, struggling in a relationship or any stressful situation may trigger a depression


What are the risk factors for depression?

Depression occurs more often in people with certain risk factors or characteristics. These include:3

  • A family history of mental illness
  • Low self-esteem
  • An anxiety disorder that began early in life
  • Abuse of alcohol or illegal drugs
  • Childhood trauma
  • Major stressful life events
  • Parental loss or other stressful circumstances during childhood
  • Marital problems such as divorce
  • Lack of Social Support
  • Low education


What are the signs and symptoms of depression?

To be diagnosed with clinical depression, one must meet the symptom criteria for major depressive disorder in a manual used by mental health providers to diagnose mental illnesses. This manual is the Diagnostic and Statistical Manual of Mental Disorders (DSM), published by the American Psychiatric Association.

To be diagnosed with depression, one must have at least five of the following symptoms over a two-week period, most of the day, nearly every day. Signs and symptoms may include:4

  • Persistent sad, anxious, or “empty” feelings
  • Significantly reduced interest or feeling no pleasure in all or most activities
  • Feelings of hopeless and pessimist
  • Significant weight loss or weight gain
  • Insomnia or increased desire to sleep
  • Restlessness or slowed behavior
  • Fatigue or loss of energy
  • Feeling guilty or worthless
  • Trouble making decisions, or trouble thinking or concentrating
  • Recurrent thoughts of death or suicide


How is depression diagnosed?

Many tests can be performed to diagnose depression:5

  • Physical examination: Some depression could be linked to a physical health problem. Therefore it is important for the doctor to perform a physical examination and ask questions about one’s health
  • Laboratory tests: Hormonal problems, especially thyroid and parathyroid problems could cause depression. A test of the thyroid and a complete blood test are required
  • Psychological evaluation: Questions about one’s symptoms, thoughts, and feelings are filled out in a questionnaire
  • DSM-5: The criteria of depression listed in the fifth edition of this manual is used to diagnose depression


How is depression treated?

The most common treatments of depression are medication and psychotherapy.6

  • Medications: These medications are commonly known as antidepressants that target neurotransmitters in the brain. The more commonly used medications are from the following classes:
    • Selective serotonin reuptake inhibitors
    • Serotonin-norepinephrine reuptake inhibitors
    • Atypical antidepressants
    • Serotonin modulators


  • Psychotherapy: Psychological therapy is recommended because it showed to be effective in improving depression. It helps the patient to adjust to crisis, stress and difficulties and to eliminate the negativity and pessimism replacing them with positive thinking. It also helps the patient to find better ways to cope with stress and solve every day’s problems.



  1. Marcus, Marina, et al. "Depression: A global public health concern." Retrieved February 7 (2012): 2014.
  2. Depression (NIMH RSS) https://www.nimh.nih.gov/health/topics/depression/index.shtml#part_145395 (Accessed December 20, 2015)
  3. Patient information: Depression in adults (Beyond the Basics) (Depression in adults) http://www.uptodate.com/contents/depression-in-adults-beyond-the-basics (Accessed December 20, 2015)
  4. Depression Center: Symptoms, Causes, Medications, and Therapies (WebMD) http://www.webmd.com/depression/ (Accessed December 20, 2015)
  5. Depression (major depressive disorder) (Depression (major depression) Tests and diagnosis) http://www.mayoclinic.org/diseases-conditions/depression/basics/tests-diagnosis/con-20032977 (Accessed December 20, 2015)
  6. Depression (major depressive disorder) (Depression (major depression) Treatments and drugs) http://www.mayoclinic.org/diseases-conditions/depression/basics/treatment/con-20032977 (Accessed December 20, 2015)