Major depression is a common and serious disorder with significant societal impact. The review of global epidemiological data shows that major depression (MDD) has a wide range of prevalence across countries, with lifetime prevalence estimates varying from 1.0% to 19.0%, and 12-month prevalence from 0.3% to 10%. These variations are influenced by both substantive and methodological factors. Cross-national data consistently show that MDD is associated with adverse outcomes, including difficulties in role transitions, reduced role functioning, and increased risk of physical disorders and suicide. Socio-demographic correlates such as gender, age, marital status, and income are consistently linked to MDD. Women are twice as likely as men to have MDD, and individuals who are separated or divorced have higher rates of MDD than those who are married. Age-related patterns show that MDD is more common in younger age groups, with the median age of onset typically in the early to mid-20s. The course of MDD is often chronic and recurrent, with significant persistence across countries. The association between MDD and physical disorders is strong, with MDD increasing the risk of chronic physical conditions and mortality. MDD is also linked to reduced work performance, lower earnings, and increased risk of early mortality. The review highlights the need for improved treatment and understanding of MDD's impact on society. Despite these findings, treatment rates remain low globally, and further research is needed to address the burden of MDD on individuals and society.Major depression is a common and serious disorder with significant societal impact. The review of global epidemiological data shows that major depression (MDD) has a wide range of prevalence across countries, with lifetime prevalence estimates varying from 1.0% to 19.0%, and 12-month prevalence from 0.3% to 10%. These variations are influenced by both substantive and methodological factors. Cross-national data consistently show that MDD is associated with adverse outcomes, including difficulties in role transitions, reduced role functioning, and increased risk of physical disorders and suicide. Socio-demographic correlates such as gender, age, marital status, and income are consistently linked to MDD. Women are twice as likely as men to have MDD, and individuals who are separated or divorced have higher rates of MDD than those who are married. Age-related patterns show that MDD is more common in younger age groups, with the median age of onset typically in the early to mid-20s. The course of MDD is often chronic and recurrent, with significant persistence across countries. The association between MDD and physical disorders is strong, with MDD increasing the risk of chronic physical conditions and mortality. MDD is also linked to reduced work performance, lower earnings, and increased risk of early mortality. The review highlights the need for improved treatment and understanding of MDD's impact on society. Despite these findings, treatment rates remain low globally, and further research is needed to address the burden of MDD on individuals and society.