Major depressive disorder (MDD)

Major depressive disorder is a mood disorder defined by persistent low mood or loss of interest lasting at least two weeks alongside other symptoms.

Beyond sadness, the diagnosis involves changes in sleep, appetite, energy and concentration, feelings of worthlessness or guilt, slowed or restless movement, and sometimes thoughts of death. Symptoms must cause real difficulty with work, relationships or daily life. Episodes can occur once or recur over a lifetime, and severity ranges from mild to disabling. The disorder affects adults of all ages and is more often diagnosed in women.

Assessment is clinical, based on a structured interview and standardized questionnaires, with medical causes such as thyroid disease ruled out. Established care includes psychotherapy and prescription antidepressants. Cannabidiol has been examined in early research on mood, and there is no approved use of cannabinoids for depression; anyone with persistent symptoms is best served by a clinician's evaluation.