Depression Defined

Depression (major depressive disorder or clinical depression) is one of the most common brain health conditions, affecting more than 280 million people worldwide (WHO). Depression causes severe symptoms that affect how you feel, think, and handle daily activities, such as sleeping, eating, or working. Although it is common for people to have short-term mood fluctuations, major depression with moderate to severe intensity can become a serious life-altering condition. Depression is a leading cause of disability around the world, and a major contributor to the overall global burden of disease.

Some forms of depression are slightly different, or may develop under unique circumstances, such as:

Persistent depressive disorder, or dysthymia

  • Depressed mood that lasts for at least two years
  • May have episodes of major depression along with periods of less severe symptoms

Postpartum depression

  • Major depression experienced during pregnancy or after delivery that may make it difficult for new mothers to complete daily care activities for themselves and/or for their babies

Psychotic depression

  • Occurs when a person has severe depression plus some form of psychosis, such as delusions or hallucinations

Seasonal affective disorder

  • Characterized by the annual onset of depression during the winter months, when there is less natural sunlight.
  • Typically accompanied by social withdrawal, increased sleep, and weight gain

Current research suggests that depression is caused by a combination of genetic, biological, psychological and environmental risk factors. For youth and teens, depression is a risk factor for developing other brain health conditions and symptoms, as well as suicide.


To be diagnosed with depression, the symptoms must be present for at least two weeks. Depression can happen at any age, but often begins in adulthood.

Symptoms of depression can include:

  • Persistent sad, anxious, or “empty” mood
  • Feelings of hopelessness, or pessimism
  • Irritability
  • Feelings of guilt, worthlessness, or helplessness
  • Loss of interest or pleasure in hobbies and activities
  • Decreased energy or fatigue
  • Moving or talking more slowly
  • Feeling restless or having trouble sitting still
  • Difficulty concentrating, remembering, or making decisions
  • Difficulty sleeping, early morning awakening, or oversleeping
  • Appetite and/or weight changes
  • Thoughts of death or suicide, or suicide attempts
  • Aches or pains, headaches, cramps, or digestive problems without a clear physical cause and/or that do not ease even with treatment


Depression can co-occur with other serious medical conditions such as diabetes, cancer, heart disease, and Parkinson’s disease. These conditions are often worse when depression is present.

If You Are In Crisis

Call the toll-free National Suicide Prevention Lifeline at 1-800-273-TALK (8255), available 24 hours a day, 7 days a week. The service is available to everyone. All calls are confidential. Contact social media outlets directly if you are concerned about a friend’s social media updates or dial 911 in an emergency.

If you are thinking about harming yourself or thinking about suicide:

  • Tell someone who can help right away.
  • Call your licensed mental health professional if you are already working with one.
  • Call your doctor or health care provider.
  • Go to the nearest hospital emergency department or call 911.

By the Numbers

280 million

People affected worldwide by depression


Number of people who die from suicide every year

$1 Trillion

Estimated annual cost to the global economy from depression and anxiety due to lost productivity


Share of people with post-traumatic stress (PTS) that also suffer from Major Depressive Disorder (MDD)

Learn More About Depression

Learn more through interviews with researchers, advocates, and those who have firsthand experience living with depression.
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One Mind is forging a bright future for those who live with depression.


ASPIRe (Applications for Serious Psychiatric Illness Recovery) is One Mind’s initiative to enable youth with Serious Psychiatric Illness to receive gold-standard, individualized care that has been shown to dramatically improve outcomes.
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Rising Star Awards

These competitive grants fund pivotal, innovative research from the most promising leaders in neuropsychiatry, accelerating discoveries of the causes of and cures for brain illnesses and injuries.
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The Healthy Brains Global Initiative (HBGI) is a global effort to mobilize US$10 billion for brain health research that will ultimately benefit people living with neurological and mental health disorders.
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Research Updates

One Mind funds critical research that is changing the face of neuropsychiatry. Check out the latest studies whose findings could spark hope for those living with depression.