Depression

Depression is a common but serious mood disorder that causes persistent feelings of sadness and loss of interest, affecting how a person thinks, feels, and handles daily activities.

How It Differs From Ordinary Sadness

Sadness is a normal, temporary emotional response to a difficult event. Depression is more persistent — typically lasting most of the day, nearly every day, for at least two weeks — and often occurs without an obvious trigger, or persists well beyond what the triggering event would explain. Our understanding anxiety and depression overview covers how depression and anxiety often overlap and when to seek help more broadly.

Symptoms

Beyond low mood, depression typically involves loss of interest in previously enjoyed activities, changes in appetite or weight, sleep disturbances, fatigue, difficulty concentrating, feelings of worthlessness, and, in more severe cases, thoughts of death or self-harm. Our symptoms of depression guide covers this in more depth.

What Causes It

Depression results from a complex interaction of genetics, brain chemistry, hormonal changes, and life circumstances — it's not a personal weakness or something a person can simply "snap out of."

Diagnosis and Risk Factors

A doctor diagnoses depression through a clinical evaluation of symptoms, their duration, and how much they affect daily functioning — there's no single test that confirms it, though blood tests may be used to rule out other causes (like a thyroid problem) with similar symptoms. Factors that raise the risk of depression include a family history of depression or other mood disorders, a personal history of trauma or major loss, chronic illness or chronic pain, and certain life circumstances like prolonged stress or social isolation — though having one or more of these doesn't mean depression is inevitable.

Treatment

Psychotherapy (particularly cognitive behavioral therapy), medication (antidepressants), or a combination of both are effective for most people. Lifestyle factors like regular exercise, adequate sleep, and social connection provide meaningful additional support, though they generally work best alongside, not instead of, professional treatment for clinical depression.