Half of the global population will have a mental disorder by age 75, study finds

One in two people globally will experience a mental health disorder by the age of 75, a large-scale study has found.

The study, published in Lancet Psychiatry and conducted jointly by researchers from the University of Queensland and Harvard University, examined data from 156,000 people in 29 countries. The data, which covered the years 2001 to 2022, was drawn from the largest ever coordinated series of face-to-face interviews, known as the World Health Organisation’s World Mental Health Survey initiative. In the surveys, a fully structured psychiatric diagnostic interview was used to assess age of onset, lifetime prevalence, and morbid risk of 13 mental disorders (as classified by the Diagnostic and Statistical Manual of Mental Disorders, or DSM) until age 75 years . The authors analysed the data by sex but did not investigate ethnicity.

“The surveys were geographically clustered and weighted to adjust for selection probability,” the authors write, adding that “standard errors of incidence rates and cumulative incidence curves were calculated using the jackknife repeated replications simulation method, taking weighting and geographical clustering of data into account.”

One of the two lead authors, Professor John McGrath from the University of Queensland’s Brain Institute, said the results demonstrated the high prevalence of mental health disorders. “The most common were mood disorders such as major depression or anxiety,” he said.

The morbid risk of any mental disorder by age 75 years was 46·4% for men and 53·1% for women.

Women more likely to develop PTSD

Amongst women, the three most common mental health disorders were depression, specific phobia, and PTSD, while for men, they were alcohol abuse, depression, and specific phobia. The median age of onset for mental health disorders was 19 for men and 20 for women, the research found. “This lends weight to the need to invest in basic neuroscience to understand why these disorders develop,” McGrath said.

The other lead author, Professor Ronald Kessler of Harvard University, said investment was needed in mental health services with a particular focus on young people.

“Services need to be able to detect and treat common mental disorders promptly, and be optimised to suit patients in these critical parts of their lives,” he said.

“By understanding the age at which these disorders commonly arise, we can tailor public health interventions and allocate resources to ensure that appropriate and timely support is available to individuals at risk.”

The authors note that “information on the frequency and timing of mental disorder onsets across the lifespan is of fundamental importance for public health planning” and that “broad, cross-national estimates of this information from coordinated general population surveys were last updated in 2007.”

The researchers said the outcomes provided valuable insights into the frequency and timing of mental disorder onset.