What is depression?

We all feel sad, helpless, or inadequate at some point in our lives. For most of us, these feelings are completely normal responses to stressful or unpleasant events that we experience, like financial struggles or the end of a romantic relationship. Our negative feelings might be painful and overwhelming, but they pass and become less intense as time goes by.
When your mood is extremely sad or negative most days and gets worse or more intense over time, you may have a mood disorder. A mood disorder is a serious change or disturbance in mood that causes a person to experience extreme or overpowering emotions and affects their ability to function normally. Major depressive disorder, or depression, is one of the most common mood disorders in the US, and causes extreme, persistent feelings like sadness and hopelessness, which can have debilitating effects on a person’s physical and mental health.

How does your brain work most of the time?

Your brain is constantly working to help you respond to your experiences. To do this, it relies on chemical messengers called neurotransmitters. Neurotransmitters are powerful communication tools that help different parts of your brain control many of your body’s functions, including behavioral processes like your sleep and appetite, and emotional processes like your mood and concentration. As you go through life, neurotransmitters interact with targets throughout the brain to help you respond to situations in an appropriate and healthy way.

What can go wrong?

Sometimes neurotransmitters stop working properly and cause problems throughout the brain’s communication system. One situation, called a chemical imbalance, can produce changes in different aspects of your mental and physical health. Many scientists believe that the severe behavioral and emotional changes found in depression are caused by imbalances in or malfunctions of neurotransmitters called monoamines. Monoamines are found in large concentrations in your body’s limbic system, which controls your emotions, sleep, appetite, and memory. When concentrations of monoamines are too low, symptoms of depression appear.
Neurotransmitters and depression
NeurotransmitterSymptoms or behaviors
Low norepinephrinedecreases in energy or motivation, poor attention and memory
Low serotoninincreases in depressed mood, food cravings, problems sleeping
Low dopamineincreases in cravings, compulsive behavior; decreases in satisfaction


Major depressive disorder changes how a person feels and acts during a period of time called a depressive episode.
Depressive episodes: during this time, the person feels extremely sad every day and the feeling lasts for a minimum of two weeks. Sadness is subjective and different for everyone, so before you label or diagnose someone who is sad with depression, it’s important to think about whether or not their behavior is noticeably different from how they usually act in similar circumstances. More specific symptoms must occur every day for at least two weeks and can include:
  • feeling blue or sad more often than not
  • feeling like life isn’t fun or pleasurable anymore
  • losing interest in things that used to be a huge part of their life
  • changes in appetite and weight, like eating significantly more and gaining weight, or not eating at all
  • changes in sleep quality or amount of sleep, like sleeping less, or sleeping more but still feeling tired
  • changes in speech, like becoming less talkative
  • psychomotor agitation, like handwringing, pacing, or tapping the foot
  • feelings of worthlessness or guilt
  • low self-esteem
  • thinking about death or wishing for death
Suicide: thoughts of suicide are the most serious symptom of depression. When people consistently experiences extreme symptoms like the ones listed above, they may sometimes begin to think that death is the only way for them to escape their pain. Because they may also feel that their future is hopeless and nothing will get better, they are much more likely to act on the thoughts that they have about death. As their depression becomes more severe, their risk of suicide also increases.
Specific warning signs for suicide include:
  • frequent, intense, or long lasting suicidal ideation, or thoughts about killing oneself
  • stating that there is no reason to live
  • feeling trapped or like they are a burden to others
  • increasing alcohol or drug use
  • giving away possessions or saying goodbye in a way that seems final
If you feel like you or someone you know may be at risk, please reach out for help by contacting the National Suicide Prevention Hotline at 1-800-273-8255.

What causes depression?

Like most mood disorders, depression doesn’t have a single cause. Instead, it is the result of the multiple factors that interact to create chemical imbalances in your brain.
  • Biological factors: if one of your family members has a mood disorder like depression, you are much more likely to develop one yourself. Even other mental illnesses, like schizophrenia or alcoholism, increase your risk of developing depression.
  • Psychological factors: stressful or negative life events, like death in the family, divorce, or loss of a job, often trigger depression. When you experience trauma or stress consistently and chronically, you are much more likely to have depression..
  • Behavioral factors: increases in alcohol consumption or drug use can lead to the development of depression and can often make symptoms worse.
  • Social factors: lack of social support, like meaningful relationships with peers or family, is associated with symptoms of depression
Factors related to mood disorders

How common is depression?

About 5% of adults around the world and 6.9% of adults in the US deal with depression at some point during their life. You are more likely to experience depression if you are female, have a medical condition like cancer or heart disease, and live in an area with low access to healthcare and employment. The high prevalence of depression has made suicide a significant public health problem in the US, and in 2013 it was the 10th leading cause of death. Rates of suicide are especially high among vulnerable populations like military veterans, individuals who identify as lesbian, gay, bisexual, transgender, or questioning, and young people between the ages of 15 and 24.

Is it possible to prevent depression?

Most scientists and mental health practitioners say that depression is not preventable and can happen to anyone at any time. Instead of prevention, they stress the importance of managing depressive episodes once they start. Some strategies that might improve coping mechanisms and decrease the severity or length of symptoms include developing healthy habits like eating nutrient dense foods, exercising, sleeping regularly, avoiding drugs and alcohol, and reaching out to family and friends.

How is depression treated?

Treatment for depression is usually integrative. This means that psychiatric, psychological, and behavioral interventions are combined to take care of the specific needs and symptoms of the patient. The treatments work together to restore normal mood and improve the person’s ability to cope with the world around them.
Psychiatric treatments:
  • Medications for major depressive disorder are called antidepressants. Antidepressants work by improving the effects of neurotransmitters in the brain. Some focus on blocking the reabsorption of specific neurotransmitters. These include serotonin reuptake inhibitors (SSRIs), serotonin and norepinephrine reuptake inhibitors (SNRIs) and norepinephrine and dopamine reuptake inhibitors (NDRIs). Other antidepressants, like monoamine oxidase inhibitors (MAOIs) focus on increasing neurotransmitter levels by regulating the enzyme (called monoamine oxidase) that is usually involved in reabsorbing them into the brain.
  • Another medical treatment for depression is electroconvulsive therapy, or ECT, which involves placing electrodes on a person’s head to pass electrical currents through their brain. This is often used as a way to improve neurotransmitter functioning when a person isn’t improving after taking antidepressants.
The effect of electroconvulsive therapy on the release of neurotransmitters
  • Psychotherapy does not address the underlying causes of depression, but it can improve functioning both during and after depressive episodes. One of the most effective psychotherapies for major depressive disorder is cognitive behavioral therapy (CBT). CBT focuses on identifying negative thoughts, emotions, beliefs, and behaviors and replacing them with more positive ones. This helps patients cope with old traumas as well as new stressful situations. Other forms of therapy focus on improving social relationships and setting long term goals. Psychotherapy is often combined with medication or other psychiatric treatments.
Behavioral treatments:
  • Behavioral interventions for depression typically involve developing healthy lifestyle habits like exercising, meditating, listening to music, eating healthy foods, and sticking to a consistent sleep schedule.

Consider the following:

  • People around the world experience mood disorders, but some cultures use different terms to describe them. For example, people in Latin America use the word “susto” to describe a mental illness with symptoms similar to depression. Susto occurs when a person goes through a life event that is so traumatic, their soul leaves their body. It can cause problems with sleep and appetite, feelings of sadness and low self-worth, decreased interest in activities, and sometimes results in suicide or death. So, when you think about depression, remember to be mindful of cultural differences and context – it may help you better understand how the illness may progress and be treated within specific populations.
  • While depression is a treatable mental illness, many people avoid seeking treatment. Why? In the United States, stigmas about depression and other mental illnesses are often the cause. In our culture, it is common to incorrectly believe that depression is a sign of weakness or a bad attitude - many people don’t think of depression as a real medical issue. As a result, those who experience depression may feel like there is something wrong with them - they feel guilty, hopeless, or ashamed that they can’t “just get over it.” To help change negative assumptions about depression, we should start thinking and talking about depression in the same way that we talk about other medical issues. If a person was diagnosed with cancer, wouldn’t we encourage them to try chemotherapy or radiation therapy? If a person burned their arm, wouldn’t we tell them to go to the hospital? When we approach mental illness from the same perspective, we can help empower people with depression to seek treatment and recover.


This article is licensed under a CC-BY-NC-SA 4.0 license. https://creativecommons.org/licenses/by-nc-sa/4.0/

Additional references:

  • American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). Arlington, VA: American Psychiatric Publishing.
  • CDC National Suicide Statistics at a Glance. (January 28, 2014).
  • NIMH Any Mood Disorder Among Adults. (2015).
  • NIMH Mental Health Medications. (2015).