Knowing at what age mental illness usually begins is very important information for psychologists. When it is known when a disorder usually starts, early preventative measures and early interventions can be performed in a timely manner. This improves the long-term well-being of the patient compared to a situation where therapy begins years after the onset of a disorder.

To provide strong estimates of when mental illness begins, data from as many patients as possible should be integrated. This is why Solmi and colleagues (2021) just conducted a meta-analysis of 192 studies investigating the onset of mental disorders. A meta-analysis is a statistical analysis that integrates the results of many different scientific studies. It has the advantage of having a larger sample size, increasing statistical power and making analysis less likely to be influenced by the characteristics of individual studies.

Overall, the study includes data from more than 700,000 patients diagnosed with a mental disorder. In addition to the age of onset for various disorders, the scientists also analyzed the percentage of people who developed a mental disorder before the ages of 14, 18 and 25 years.

Mental disorders often started earlier than expected

The authors found that the peak age of onset of mental disorders was 14.5 years. About 34.6% of patients developed a disorder before the age of 14, 48.4% before the age of 18, and 62.5% before the age of 25. This shows that for nearly 50% of patients, mental disorders begin before they reach adulthood, emphasizing the importance of early intervention and preventative measures for adolescent mental health issues.

In a second step, the scientists also analyzed the age of onset for various forms of mental disorders. Here are some of the findings:

Neurodevelopmental disorders: 5.5 years old
Anxiety and phobias: 5.5 years old
Obsessive-compulsive disorder: 14.5 years old
Eating disorders: 15.5 years old
Stress disorders: 15.5 years old
Addiction: 19.5 years old
Schizophrenia: 20.5 years old
Personality disorders: 20.5 years old
Depression and other forms of mood disorders: 20.5 years

There were no significant differences between male and female patients regarding onset age.

If there is one thing the study clearly shows, it is that adolescent mental health issues need to be taken seriously. People often have the idea that most mental health conditions start in adulthood, and only developmental disorders begin in childhood. When teens exhibit or even show mental health problems, parents sometimes think they will "grow up" or "it's just a stage". Research shows that such ideas are wrong, and mental problems in adolescence need to be addressed as in almost 50%, the disorders start at this stage of life.

Source: Psychology Today