There is a 1.5- to 2-fold increased risk of cardiovascular disease, independent of other known risk factors, and is itself linked directly or indirectly to risk factors such as smoking and obesity. People with major depression are less likely to follow medical recommendations for treating and preventing cardiovascular disorders, further increasing their risk of medical complications. Cardiologists may not recognize underlying depression that complicates a cardiovascular problem under their care. Epidemiology
Major depressive disorder affected approximately 163 million people in 2017 (2% of the global population). The percentage of people who are affected at one point in their life varies from 7% in Japan to 21% in France. In most countries the number of people who have depression during their lives falls within an 8–18% range.In the United States, 8.4% of adults (21 million individuals) have at least one episode within a year-long period; the probability of having a major depressive episode is higher for females than males (10.5% to 6.2%), and highest for those aged 18 to 25 (17%). Among adolescents between the ages of 12 and 17, 17% of the U.S. population (4.1 million individuals) had a major depressive episode in 2020 (females 25.2%, males 9.2%). Among individuals reporting two or more races, the US prevalence is highest.Major depression is about twice as common in women as in men, although it is unclear why this is so, and whether factors unaccounted for are contributing to this.
Both symptoms and treatment among the elderly differ from those of the rest of the population.Major depression was the leading cause of disease burden in North America and other high-income countries, and the fourth-leading cause worldwide as of 2006. In the year 2030, it is predicted to be the second-leading cause of disease burden worldwide after HIV, according to the WHO. Delay or failure in seeking treatment after relapse and the failure of health professionals to provide treatment are two barriers to reducing disability. Comorbidity
Major depression frequently co-occurs with other psychiatric problems. The 1990–92 National Comorbidity Survey (US) reported that half of those with major depression also have lifetime anxiety and its associated disorders, such as generalized anxiety disorder. Anxiety symptoms can have a major impact on the course of a depressive illness, with delayed recovery, increased risk of relapse, greater disability and increased suicidal behavior. Depressed people have increased rates of alcohol and substance use, particularly dependence, and around a third of individuals diagnosed with attention deficit hyperactivity disorder (ADHD) develop comorbid depression. Post-traumatic stress disorder and depression often co-occur. Depression may also coexist with ADHD, complicating the diagnosis and treatment of both. Depression is also frequently comorbid with alcohol use disorder and personality disorders. Depression can also be exacerbated during particular months (usually winter) in those with seasonal affective disorder. While overuse of digital media has been associated with depressive symptoms, using digital media may also improve mood in some situations.Depression and pain often co-occur.