Major depressive disorder (MDD)
Overview
Plain-Language Overview
Major depressive disorder (MDD) is a common mental health condition that affects the brain and how a person feels, thinks, and handles daily activities. It causes persistent feelings of sadness, loss of interest in activities once enjoyed, and can lead to changes in sleep, appetite, and energy levels. People with MDD may experience difficulty concentrating, feelings of worthlessness, and sometimes thoughts of death or suicide. This disorder impacts emotional well-being and can interfere with work, relationships, and overall quality of life. It is a serious condition that involves changes in brain chemistry and function.
Clinical Definition
Major depressive disorder (MDD) is a psychiatric condition characterized by a persistent depressed mood or loss of interest or pleasure in nearly all activities for at least two weeks. It involves dysregulation of monoamine neurotransmitters such as serotonin, norepinephrine, and dopamine, often linked to genetic, environmental, and psychosocial factors. The disorder is associated with significant functional impairment and increased risk of morbidity and mortality, including suicide. Pathophysiologically, it involves altered neuroplasticity, hypothalamic-pituitary-adrenal axis dysfunction, and inflammatory changes. Diagnosis requires exclusion of other medical or psychiatric causes. MDD is a leading cause of disability worldwide and requires timely recognition for effective management.