Major depressive disorder is a pervasive state that disables the capacity to feel pleasure and persists for at least two weeks. This condition leaves the sufferer trapped in a cycle of worthlessness and hopelessness that requires clinical attention.
Major depressive disorder was formally codified by a group of US clinicians in the mid-1970s and adopted by the American Psychiatric Association in the 1980 version of the Diagnostic and Statistical Manual of Mental Disorders. This shift marked a departure from earlier classifications like depressive neurosis and depressive reaction.
Major depressive disorder affects approximately 163 million people worldwide as of 2017 and causes the second-most years lived with disability globally. It trails only low back pain in global disability burden and is predicted to become the second-leading cause of disease burden worldwide by 2030.
Major depressive disorder involves a combination of genetic, environmental, and psychological factors that account for about 40% of the risk. A 2022 review found no consistent evidence supporting the link between serotonin levels and depression, challenging the monoamine theory.
Norwegian Prime Minister Kjell Magne Bondevik became the highest-ranking world leader to admit to suffering from a depressive episode while in office in 1998. This move attracted international attention and helped reduce stigma surrounding mental illness.
Major depressive disorder genetic studies identified 44 variants in a 2018 genome-wide association study and 102 variants found in 2019. These discoveries provide a deeper understanding of the heritable components of the disorder alongside environmental factors.