Depression

7 min read · Reviewed June 2026

Depression is more than feeling sad. NIMH describes it as a persistently low or empty mood, or loss of interest in things you used to enjoy, most of the day nearly every day for at least two weeks — to the point that it affects sleep, eating, work, and relationships. It is common, and importantly, it is treatable. The earlier treatment begins, the more effective it tends to be.

Common forms

NIMH describes two common types. Major depression involves low mood or loss of interest most of the time for at least two weeks. Persistent depressive disorder (also called dysthymia) is a lower-grade depression that lasts much longer — usually at least two years.

Depression can also take specific forms, including seasonal affective disorder, which follows a seasonal pattern, and perinatal depression, which can occur during pregnancy or after childbirth and is more than the temporary "baby blues."

Why activity matters: behavioral activation

Depression often creates a loop: low mood leads to doing less, doing less means fewer rewarding experiences, and that pushes mood lower still. Behavioral activation (BA) is a practical, evidence-based approach that targets this loop directly by gradually rebuilding activity.

A common BA method, used in NHS self-help workbooks, is to plan three kinds of activities each week: routine (daily basics), necessary (things that cause problems if neglected, like bills or appointments), and pleasurable (things you value or enjoy). The goal is to act first and let mood follow, rather than waiting to feel motivated.

BA is recommended in UK NICE guidance, and a 2014 meta-analysis of 26 randomized trials (Ekers and colleagues) found it more effective than control conditions and broadly comparable to other established therapies for depression.

Treatment options

Most people with depression benefit from treatment: talk therapy (such as CBT or behavioral activation), medication, or a combination. A healthcare provider can help you weigh the options based on your symptoms and history.

Key points

Depression is low mood or loss of interest most days for two weeks or more — and it is treatable.
Major depression and persistent depressive disorder (dysthymia, lasting 2+ years) are the two common types.
Behavioral activation rebuilds rewarding activity to break the low-mood-and-withdrawal loop.
Therapy, medication, or both help most people; earlier treatment works better.

When to seek help

Talk with a healthcare provider if you have symptoms most of the day, nearly every day, for at least two weeks. If you or someone you know is having thoughts of suicide, use the urgent-help numbers at the top of this screen now.