Depression is defined by a persistently low or empty mood, or loss of interest in activities, lasting most of the day nearly every day for at least two weeks, according to the World Health Organization and the U.S. National Institute of Mental Health (NIMH). This guide lists the symptoms health agencies use to identify it, who is most affected, evidence-based coping steps, and where to get crisis help if needed.
What Counts as Depression
The World Health Organization (WHO) describes depression as a common mental disorder involving a depressed mood or a loss of pleasure or interest in activities over long periods of time. The U.S. National Institute of Mental Health (NIMH) states that to be diagnosed, a person must have depressed mood or loss of interest, plus other symptoms, present most of the day, nearly every day, for at least two weeks. Both agencies note this differs from ordinary mood changes or short-lived sadness.
Symptoms to Watch For
WHO and NIMH list overlapping sets of symptoms. A person does not need every symptom on the list — NIMH notes some people experience only a few while others experience many.
Persistent sad, anxious, empty, or irritable mood (WHO, NIMH)
Loss of interest or pleasure in activities previously enjoyed (WHO, NIMH)
Poor concentration or difficulty making decisions (WHO, NIMH)
Feelings of excessive guilt, worthlessness, or hopelessness (WHO, NIMH)
Disrupted sleep — insomnia, early waking, or oversleeping (WHO, NIMH)
Changes in appetite or unplanned weight change (WHO, NIMH)
Fatigue or feeling slowed down (WHO, NIMH)
Physical aches, headaches, or digestive problems with no clear physical cause (NIMH)
Thoughts of death or suicide (WHO, NIMH)
NIMH adds that in children, irritability may appear instead of sadness, and that depression can also show up as increased anger, withdrawal from family and friends, impulsivity, or greater use of alcohol or drugs.
Who Is More Likely to Be Affected
WHO estimates that 5.2% of adults worldwide were living with depression in 2023 — about 322 million people. The rate was 4.1% among men and 6.2% among women, making depression roughly 1.5 times more common in women, per WHO. Adults aged 70 and older had a prevalence of 5.4%. WHO also reports that more than 10% of pregnant and postpartum women experience perinatal depression. Cleveland Clinic states that about 3 in 10 adults receive a depression diagnosis at some point in their life, while noting the true share may be higher since many people never seek medical help.
Type
Typical pattern
Major depressive disorder
Symptoms most of the day, nearly every day, for at least 2 weeks
Persistent depressive disorder
Milder symptoms lasting 2 years or more
Seasonal affective disorder
Episodes tied to specific seasons, usually autumn/winter
Perinatal depression
During pregnancy or after childbirth; affects over 10% of pregnant/postpartum women (WHO)
Premenstrual dysphoric disorder
Linked to the menstrual cycle
Steps to Recognize and Cope With Depression
Track mood and symptoms for two weeks. WHO and NIMH both use the threshold of depressed mood or loss of interest present most of the day, nearly every day, for at least two weeks as the marker that distinguishes depression from normal sadness.
Keep a regular sleep schedule and stay physically active. Cleveland Clinic lists a consistent sleep routine and activities such as exercise, meditation, or yoga as supportive measures that can help manage symptoms.
Stay connected to other people. Cleveland Clinic notes that spending time with loved ones supports overall wellbeing during a depressive period, and that a loved one may notice changes in mood or behavior before the person does.
Seek a professional evaluation. NIMH recommends contacting a healthcare provider when symptoms persist; psychotherapy approaches such as cognitive behavioral therapy and interpersonal therapy are described by NIMH as evidence-based treatments.
Discuss medication if a provider recommends it. WHO notes antidepressants such as fluoxetine (an SSRI) may be used for moderate-to-severe depression, often combined with psychological treatment. NIMH states antidepressants typically take 4 to 8 weeks to show effect, and flags that the FDA warns of increased suicidal thoughts in patients under 25 starting these medications.
Ask about further options if first treatments don't work. For treatment-resistant cases, NIMH lists esketamine, electroconvulsive therapy (ECT), and repetitive transcranial magnetic stimulation (rTMS) as options a provider may consider.
Treat thoughts of death or suicide as urgent. If these occur, NIMH directs people in the U.S. to call or text the 988 Suicide and Crisis Lifeline, or dial 911 in a life-threatening emergency.
Suicide Risk and Why Early Recognition Matters
WHO states that people with depression face an increased risk of suicide, and that around 727,000 people died by suicide globally in 2021 — the most recent figure in its fact sheet — with suicide ranking as the third leading cause of death among 15- to 29-year-olds. WHO lists adverse life events such as unemployment, bereavement, or traumatic experiences, along with physical inactivity and harmful alcohol use, as factors associated with higher risk.
Sometimes, a loved one may see changes in your mood or behavior before you do.
— Cleveland Clinic
Questions
How long do symptoms need to last to be considered depression?
Both WHO and NIMH use the same threshold: depressed mood or loss of interest, plus other symptoms, present most of the day, nearly every day, for at least two weeks.
What is the difference between major depressive disorder and persistent depressive disorder?
NIMH describes major depressive disorder as interfering symptoms lasting at least 2 weeks, while persistent depressive disorder involves milder symptoms that continue for 2 years or more.
Is depression more common in women than men?
Yes. WHO reports a 2023 global prevalence of 6.2% in women versus 4.1% in men, making depression about 1.5 times more common in women.
How long do antidepressants take to work?
NIMH states antidepressants typically take 4 to 8 weeks to show an effect.
Where can someone get immediate help for suicidal thoughts?
NIMH directs people in the United States to call or text the 988 Suicide and Crisis Lifeline, or dial 911 for a life-threatening emergency.
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