Half of people worldwide at risk of developing mental health condition by age 75, per new study

By the age of 75, half of people worldwide can expect to experience a mental health disorder, according to the finding of a large study of more than 156,000 people across 29 countries.

The study, published last week in The Lancet Psychiatry, analyzed answers that participants provided between 2001 and 2022 in response to a World Health Organization survey designed to assess the prevalence of major mental health disorders. The study focused on 13 common mental health disorders, including major depressive disorder and bipolar disorder, anxiety disorders, substance use disorders, and attention-deficit/hyperactivity disorder.

Overall, 29% of male respondents and 30% of female respondents reported having had at least one of the mental health conditions in the 10 years prior to when they answered the survey’s questions. The lifetime risk that a person would develop a mental health condition by age 75 was 46% for male respondents and 53% for female ones, which the researchers estimated based on respondents’ experiences with disorders and their ages at the time of the survey, then projecting the risk of occurrence if all respondents lived for 75 years.

Mental health issues typically emerge early in life. For the first onset of mental health disorders, the peak incidence was at age 15, and the median age of onset was 19 for male respondents and age 20 for female respondents, according to the survey.

By the time they turn 20, half of those who will eventually develop a mental health disorder have already experienced signs or symptoms. “Mental health disorders are the chronic disorders of the young,” said John McGrath, a professor at the Queensland Brain Institute at the University of Queensland and a lead author of the study.

This points to the need to adopt earlier interventions to improve mental health in young people, said McGrath. Mental health disorders often first appear at critical moments in a young person’s life, when they are embarking on important personal and professional journeys.

“If this is disturbed by a disabling illness like anxiety, a social phobia, or substance use, that can have profound domino consequences across a whole range of adverse health outcomes,” said McGrath.

Which mental health disorders are most common among men and women?

The findings expand on a 2007 report based on the World Mental Health survey, which had collected answers from 85,000 people in 13 countries, and provided what was until now the most comprehensive international picture of lifetime prevalence of mental health disorders and age of onset.

This latest study has some important limitations. Cultural biases, as well as changing social and economic conditions over the course of two decades, could influence the responses people in various countries give when surveyed about their mental health.

Yet compared to the 2007 report, the study’s authors say it provides a more accurate picture of the typical age of onset of mental health disorders, and an evaluation of the risk for specific disorders rather than only broad categories. It also contributes new insights on gender differences when it comes to which disorders are most common among men and women.

For male responders, the disorder with the highest prevalence at the time of interview was alcohol abuse (14%), followed by major depressive disorder (7.5%) and specific phobias (5%). For women, the most common condition was major depressive disorder (14%), followed by specific phobias (10%) and post-traumatic stress disorder (4.5%).

The study also found that women had a much higher prevalence of anxiety disorders: 18%, compared to 11% for men. Conversely, men had a much higher risk of developing an addiction: 14.4% reported a substance use disorder, compared to 10% of women.

The prevalence of individual mental health disorders can vary greatly. For example, the most recent data from the National Institute of Mental Health shows that an estimated 4% of U.S. adults experience bipolar disorder at some point in their lives, while an estimated 31% of U.S. adults experience an anxiety disorder at some point in their lives. But cumulatively, mental health disorders are extremely common.

This finding shouldn’t minimize the debilitating effects of mental health struggles and the impact these conditions have on society at large, McGrath said, especially when younger people are unable to contribute to their full potential. “Just because it’s common […] doesn’t weaken or abrogate the fact that these people are disabled,” said McGrath.