Youth depression tied to higher risk of 66 diseases and premature death

"Our study shows that children and teenagers diagnosed with depression have a significantly higher risk of premature death, self-harm, and suffering from other diseases later in life" says Sarah E. Bergen, senior researcher at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, and corresponding author of the study. "It underscores how important it is that these children and teenagers receive the help they need and that medical personnel monitor for subsequent psychiatric and somatic diseases."

Depression is rarely diagnosed in young children but increases in prevalence through the teenage years. Previous studies have linked depression in adolescents to an increased risk of several adverse outcomes, including atherosclerosis, cardiovascular disease and premature death. Other psychiatric conditions, such as anxiety and substance use disorder, are also commonly linked.

In this study, the researchers wanted to examine whether depression at an early age might be associated with a wide spectrum of diseases diagnosed later in life. They also examined how other psychiatric conditions affected the association and whether youth depression heightened the risk of premature death.

The researchers followed almost 1.5 million Swedish girls and boys, of whom more than 37,000 were diagnosed with depression at least once between the ages of 5 and 19. When the research concluded, they were between 17 and 31 years old.

The study found that children and teenagers with depression had a higher risk of being diagnosed with 66 out of 69 examined medical conditions, including sleep disorders, type 2 diabetes, viral hepatitis, and kidney and liver diseases. Compared to those without depression, they also had a significantly higher risk of injuries, especially injuries inflicted by self-harm, and an almost six-fold higher risk of premature death.

The findings also revealed sex differences. For example, women with early onset depression were more likely to suffer injuries as well as urinary, respiratory and gastrointestinal infections. Men, on the other hand, were more likely to have obesity, thyroid gland problems, coeliac disease, connective tissue disorders and eczema.

Part of the association may be explained by other co-existing psychiatric conditions, especially substance use disorder and anxiety, which have previously been linked to risk increases for certain medical outcomes. These psychiatric conditions often appear in the same patient and therefore more studies are needed to examine the specific effect of each condition, according to the researchers.

"We need more research to understand the causality between depression and other diseases," says Marica Leone, PhD candidate at the Department of Medical Epidemiology and Biostatistics at Karolinska Institutet, and first author of the study. "Currently, we cannot say whether depression leads to an increased risk of negative health effects or whether there are other underlying factors that lead to increased risks for both depression and the diseases examined in this study. Therefore, it is important to investigate how these processes affect each other and whether we, through discovery of these disease mechanisms, can find targets for intervention and treatment to improve overall health."

The research has been funded by the European Union's Horizon 2020 research and innovation programme. Some of the authors have reported conflicts of interest: Marica Leone is an employee of Johnson & Johnson, Henrik Larsson has received personal fees from Shire/Takeda and Evolan outside the submitted work and Amy Leval is an employee of and owns stock in Johnson & Johnson.