Conditions and states of mind

Depression: a treatable illness, not just a bad mood

The main symptoms and causes of depression, how it is treated, and why it is not a matter of "weak willpower."

Last reviewed: 2026-09-24

What is depression?

Depression (major depressive disorder) is a condition in which a low mood or loss of interest lasts nearly every day for two weeks or more and gets in the way of daily life. Unlike the passing sadness everyone feels, it affects your thoughts, emotions, and body as a whole.

Depression is common. Many people experience it at least once in their lives, and it can happen to anyone regardless of gender or age.

Main symptoms

  • Feeling sad or empty most of the day
  • Much less interest or pleasure in things you used to enjoy
  • Noticeable changes in appetite or weight
  • Trouble sleeping, or sleeping too much
  • Feeling restless, or the opposite — body and thoughts slowing down
  • Tiredness and low energy
  • Feeling worthless or excessively guilty
  • Trouble concentrating or making decisions
  • Repeated thoughts of death or suicide

If several of these last for two weeks or more, it is a good idea to get a professional evaluation.

Causes

Depression rarely has a single cause. Changes in brain chemistry, genetic factors, stressful life events (a breakup, job loss, bereavement), chronic illness, and personality traits often combine.

Depression is not caused by "weak willpower." Like diabetes or high blood pressure, it is a health problem that needs treatment.

Treatment

Depression responds well to treatment. The main options are:

  • Medication: antidepressants usually take two to four weeks or more of regular use to work. Stopping on your own because you feel better can lead to relapse, so adjust the dose with your doctor.
  • Psychotherapy: approaches such as cognitive behavioral therapy (CBT) help you notice and change negative thinking patterns.
  • Lifestyle: regular sleep, light exercise, daylight, and drinking less all boost the effect of treatment.

Mild symptoms may improve with counseling alone; for moderate or more severe symptoms, medication and therapy are usually combined.

Get help right away if…

If you are thinking about dying or feel you might hurt yourself, do not go through it alone — reach out now.

  • U.S.: call or text 988 (Suicide & Crisis Lifeline, 24/7), or text HOME to 741741
  • Korea: 109 (Suicide Prevention Line, 24/7) or 1577-0199 (Mental Health Crisis Line, 24/7)
  • Elsewhere: find a local helpline at findahelpline.com
  • In immediate danger: call 911 in the U.S., or 112/119 in Korea

Curious about how you are doing?

Take the Depression Self-Check (PHQ-9) to quickly check where you are right now.

Take a self-check →

References

  • National Center for Mental Health, Korea (mentalhealth.go.kr)
  • American Psychiatric Association, Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision (DSM-5-TR)

This article provides general information and does not replace a medical diagnosis or legal advice.