What Are the 9 Causes of Depression?

Medically Reviewed on 8/19/2021
nine causes of depression
Depression is caused by a combination of biological, environmental, psychological and genetic factors. Here are the top nine causes of depression.

According to the National Institute of Mental Health, depression affects about 6.7 percent of the U.S. population. Depression is caused by a combination of biological, environmental, psychological and genetic factors.

Here are the top nine causes of depression:


  • Many people are born with a genetic risk of depression, which can then be triggered by social or environmental factors, such as stress.
  • If a person has an immediate family member who is depressed, such as a parent or sibling, that person is one and a half to three times more likely to develop depression than someone without such a family member.


  • Brain chemicals called neurotransmitters also contribute to the development of depression, with serotonin and norepinephrine appearing to play key roles.
  • These two chemicals may regulate other neurotransmitters such as dopamine and acetylcholine that can also contribute to depression.
  • According to recent studies, the hormone melatonin might also play a role in depression.


  • Illnesses can also cause depression, especially life-threatening and chronic illnesses, such as cancer, human immunodeficiency virus (HIV), autoimmune conditions and arthritis.
  • Facing disease, and possibly death is enough to make even the strongest person feel depressed.
  • Additionally, certain illnesses create chemical changes in the body that cause depression or depression-like symptoms. These illnesses may include:
  • Women who have premenstrual syndrome (PMS) or who have recently had a baby may also experience symptoms of depression.


Other substances

  • Many other substances can also cause depression, such as frequently used recreational drugs with depression-like or withdrawal symptoms, including:
  • Many environmental toxins are also suspected of being linked to depression, including these chemicals:
    • Pesticides
    • Copper
    • Aluminum
    • Mercury
    • Lead
    • Formaldehyde
  • People who suspect that they have been exposed to one of these chemicals or another toxic chemical should consult a medical professional.


  • Trauma is any event that causes severe emotional or physical injury and leaves long-lasting damage. Some of the more common causes of trauma include:
    • War
    • Crime
    • Rape
    • Accidents
    • Abuse
    • Natural disasters
    • Relationship problems
  • The trauma doesn’t need to have occurred recently for it to affect a person’s mental health. Older traumas can cause depression too.

Self-defeating thoughts

  • Depression can also be caused by repetitive self-defeating thoughts.
  • The negative messages we replay in our heads are some of the most powerful obstacles we must overcome in our lives.
  • Sadly, many of these self-defeating and self-demeaning thoughts don’t even originate within our heads. Instead, they are told to us by our parents, friends or society as we grow up.

Interpersonal conflicts

  • Depression may also be caused by feelings of not being connected with others or being in conflict with others.
  • Feelings of being alone or unwanted are perhaps two of the most powerful emotions humans can experience. Therefore, it’s not strange that feeling them can lead to depression.
  • These are very difficult feelings to deal with, especially when a person is alone or in an unsatisfying relationship.
  • In fact, social isolation and lack of social support are two predictors of suicide in people with severe depression.
  • People who think they have no one else to live for often don’t want to live for themselves.

Loss of meaning

  • Depression can be caused by a loss of meaning in a person’s life.
  • The meanings we give life can be religious, spiritual, community-based or personal. Sometimes, these beliefs are challenged. 
  • Most times, people’s beliefs will remain strong or adjust to accommodate new information.
  • However, sometimes meanings and beliefs fail, and as a result, people lose faith in their religion, country, society or job.

How is mourning different from depression?

It’s important to note that depression is not the same as mourning, although they may look similar. Many people will react in a way that resembles depression after someone they know dies or departs. This is considered normal grieving. However, if the feelings of grief persist for an extended length of time or become worse, it might become depression. In this case, the person should consult mental healthcare professionals.

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Medically Reviewed on 8/19/2021
Depression Central: https://www.psycom.net/depression.central.html

What Is Depression? https://www.psychiatry.org/patients-families/depression/what-is-depression

Depression in adults (Beyond the Basics): https://www.uptodate.com/contents/depression-in-adults-beyond-the-basics