Medical Encyclopaedia › Depression (short definition)
In brief: Depression is a serious, treatable mental illness that affects mood, drive, thinking and the body. It is widespread: one in five to six people develop it in the course of their lives.
Signs
The main features are a persistently low mood, loss of interest and pleasure, and lack of drive and rapid fatigue for at least two weeks. Sleep problems, changes in appetite, difficulty concentrating, feelings of guilt, low self-esteem, hopelessness and physical complaints such as pain are often added. Some of those affected have thoughts of not wanting to live any more.
Causes
Depression arises from an interplay of predisposition, changes in the brain’s messenger substances and stress systems, stressful life events, chronic stress and personality factors. Physical illnesses such as an underactive thyroid, chronic pain or certain medicines can also be involved.
Diagnosis
The diagnosis is made in conversation on the basis of defined criteria; questionnaires can help. Physical causes are ruled out by examination and laboratory tests. Depending on the number and severity of symptoms, mild, moderate and severe episodes are distinguished.
Treatment
Psychotherapy, such as cognitive behavioural therapy, and antidepressants such as SSRIs are effective; in moderate and severe depression, both are often combined. Antidepressants usually only take effect after two to four weeks and should not be stopped abruptly. Exercise, a regular daily structure and, in seasonal depression, light therapy help in addition. For severe, treatment-resistant courses, further procedures such as esketamine or electroconvulsive therapy are available. Digital health applications can support treatment.
Help in an acute crisis
If you are thinking about suicide, immediate help is important: in Germany, the Telefonseelsorge crisis line can be reached free of charge around the clock on 0800 111 0 111 or 0800 111 0 222; in acute danger, call the emergency number 112 or go to the nearest psychiatric hospital. For relatives: talking about it helps – do not leave the person alone.
Related terms in the encyclopaedia
Antidepressant, Selective serotonin reuptake inhibitors (SSRIs), Psychotherapy, Cognitive behavioural therapy, Dysthymia, Winter depression, Postnatal depression, Burnout, Mental health crisis
Sources
- Bundesärztekammer, KBV, AWMF: Nationale VersorgungsLeitlinie Unipolare Depression, leitlinien.de
- Stiftung Deutsche Depressionshilfe und Suizidprävention: deutsche-depressionshilfe.de
- IQWiG: gesundheitsinformation.de – Gesundheitsinformationen des Instituts für Qualität und Wirtschaftlichkeit im Gesundheitswesen
Note: This article is for general information and does not replace advice, diagnosis or treatment from a doctor or pharmacist. Last updated: October 2026.