Most mental health conditions start earlier in life than many people expect. A large international study found that half of all mental health conditions have begun by the age of 18, and around two in three by the age of 25. Understanding when conditions tend to appear helps individuals, families and health services recognise the signs sooner and seek help at the point where it can make the most difference.
This article summarises the findings of a review published in the journal Molecular Psychiatry and explains what they mean for early recognition and prevention.
Key Takeaways:
- Across all conditions studied, a mental health condition had already begun in 34.6% of people before age 14, 48.4% before age 18, and 62.5% before age 25.
- The peak age for a first condition to appear was 14.5 years, and the median (midpoint) age was 18 years.
- Different conditions tend to emerge at different life stages — from early childhood for neurodevelopmental conditions to the thirties for some mood conditions.
- Recognising conditions early, and offering support around the time they begin, is linked to better long-term outcomes.
- The findings question the traditional split between child and adult mental health services at age 18.
Mental disorders such as anxiety, depression, eating disorders, and addiction can have a significant impact on a person’s life, affecting their quality of life, relationships, employability, and more. According to current research, individuals with mental disorders have a decreased life expectancy of 10-15 years in comparison with the general population. However, early intervention at the first onset of mental disorders can improve several outcomes.
The Importance of Early Intervention
Primary indicated prevention in high-risk individuals may alter the course of some mental disorders, leading to improved outcomes. For example, early clinical care for young people with attenuated symptoms for psychosis and functional impairments can help to delay or impede the transition to psychosis.
Targeted preventive measures include screening programmes in asymptomatic individuals with significant risk factors for certain disorders – known as primary universal prevention – and public health campaigns aimed at the general population.
Such initiatives, in addition to the promotion of good mental health, may be more beneficial when young people are targeted at around the time of onset of mental disorders. However, the peak ages and ranges at onset for mental disorders are not fully established, with conflicting findings across and within current studies.
The study at a glance
Researchers carried out a systematic review and meta-analysis. This is a method that pools results from many separate studies to produce a single, more reliable estimate. Published in Molecular Psychiatry in 2022, it is the largest analysis of its kind to date.
The authors searched the PubMed and Web of Science databases for high-quality studies from the general population that reported the age at which mental health conditions began, defined using recognised diagnostic systems (the ICD and DSM). After screening, they included 192 studies covering 708,561 people from countries across every continent.
They looked at two main things: the proportion of people whose condition had begun before ages 14, 18 and 25, and the peak age at onset — for mental health conditions overall and for each diagnostic group.
Findings of the Analysis
The table below shows, for each group of conditions, the proportion of people affected by ages 14, 18 and 25, alongside the peak age at which the condition first appeared.
| Condition group | Begun by age 14 | Begun by age 18 | Begun by age 25 | Peak age at onset |
| Any mental health condition | 34.6% | 48.4% | 62.5% | 14.5 years |
| Neurodevelopmental conditions | 61.5% | 83.2% | 95.8% | 5.5 years |
| Anxiety and fear-related conditions | 38.1% | 51.8% | 73.3% | 5.5 years |
| Obsessive-compulsive and related conditions | 24.6% | 45.1% | 64.0% | 14.5 years |
| Feeding and eating conditions | 15.8% | 48.1% | 82.4% | 15.5 years |
| Conditions associated with stress | 16.9% | 27.6% | 43.1% | 15.5 years |
| Substance use and addictive behaviours | 2.9% | 15.2% | 48.8% | 19.5 years |
| Schizophrenia-spectrum and psychotic conditions | 3.0% | 12.3% | 47.8% | 20.5 years |
| Personality conditions and related traits | 1.9% | 9.6% | 47.7% | 20.5 years |
| Mood conditions (e.g. depression, bipolar) | 2.5% | 11.5% | 34.5% | 20.5 years |
The earliest to appear are neurodevelopmental conditions such as autism and attention-deficit/hyperactivity disorder (ADHD), together with some phobias and separation anxiety, typically emerging in childhood. Eating conditions, obsessive-compulsive conditions tend to cluster in the late teens to early twenties. Schizophrenia, personality and alcohol use conditions tend to follow in the mid-twenties, while post-traumatic stress, depression, generalised anxiety and bipolar conditions often appear later, into the thirties.
The researchers also noted that some conditions have a second peak later in life. A second peak in incidence for specific disorders can be found at:
- Anxiety/fear-related disorders (peak = 15.5 years)
- Obsessive-compulsive/related disorders (peak = 49.5 years)
- Disorders specifically associated with stress (peaks = 30.5 and 49.5 years)
- Substance use/addictive behaviour disorders (peak = 44.5 years)
What the findings mean for mental health services
The authors argue that the results challenge how services are often organised. Many health systems divide child and adult mental health care at age 18. Yet this analysis shows that a large share of conditions begin before that age, and that the transition years around 18 are among the most common for a first condition to appear.
The researchers suggest that services could be designed with “softer” entry points and no rigid lower age limit, so that support is continuous from childhood through adolescence into adulthood. Schools, colleges, GPs and community settings all have a role in spotting conditions early and connecting people to help.
Speak to a Specialist
If you are worried about your mental health, or about someone you care about, you do not need to wait for things to reach a crisis point. Speak to your GP or a qualified healthcare professional, who can talk through your situation and the support available to you. In an emergency, or if you are in immediate distress, contact your local emergency services or a crisis helpline.
Medical cannabis can be considered for a range of mental disorders when conventional treatments have failed. It is important to always discuss your options with a qualified health care professional. If you’d like to learn more about medical cannabis, you can complete our eligibility check to see whether a consultation might be suitable for you.
