Adolescence is a critical time for the development of mental health problems. In fact, depression is most likely to occur during adolescence and young adulthood. It’s the leading cause of disability in young people worldwide.

At least one‐quarter of young people will experience an episode of depression before 19 years of age. By year 9, students who have experienced a mental disorder are on average two years behind in academic achievement compared to those without a mental disorder.

The consequences of depression in adolescence are serious and can be lifelong. These include an increased risk of depression late in life, poor social functioning and academic achievement and reduced employment security, as well as greater risk of suicide and self‐harm.

Read more: What can parents do about their teenagers' mental health?

Many young people don’t recover from depression, despite treatment with the best available evidence‐based treatment approaches. Given the scope and impact of depression in young people, and poor recovery rates, it’s crucial to understand how to help prevent the development of depression in young people.

An increasing body of evidence indicates physical activity and exercise are effective for improving mood. We recently also examined studies to assess the efficacy of physical activity and exercise as a prevention for depression in young people. We found eight controlled research studies that examined this. These studies showed exercise and physical activity are effective as a depression-prevention approach for young people.

How much physical activity do young people need to do?

Few young people seek professional help for mental health concerns. It’s important to engage young people in places that suit them to prevent the onset of mental health problems. Prevention and early intervention are crucial and especially relevant in the education setting.

The Australian guidelines state young people should engage in 60 minutes of physical activity a day. The majority of young people don’t reach this target.

In fact, disengagement from regular exercise, physical activity and sporting clubs steadily increases during adolescence. This coincides with the average age of onset of depression.

Physical activity is an important part of the Australian Curriculum. The Australian national policy requires government schools to provide at least two hours of physical activity per week during primary education and junior secondary education. The provision of any physical education is not required as part of the senior secondary curriculum. Even during primary education and junior secondary education, the mandated 120 minutes a week doesn’t meet Australian guidelines.

Schools are a key site for the promotion of healthy behaviours. Many long-term health-related behaviours and patterns – both positive and negative – are established during the developmental phase of adolescence and early adulthood.

How do we get them to do more?

The research indicates physical activity is associated with reduced risk of depression in young people. Physical activity is an acceptable, non-stigmatising approach to promoting better mental health in young people. To meet the specific needs of young people, a physical activity program should facilitate self-reliance, motivation, and mental health and wellbeing literacy.

Motivation to engage in physical activity can be increased by offering choice of activities, increasing skills and ability to engage in physical activity, and opportunities for social connection. Schools are best placed to ensure physical activity is increased and protected within the Australian curriculum and that young people meet the Australian guidelines for physical activity each day.

Most school-based intervention studies of physical activity have used supervised programs of moderate to vigorous physical activity. These consist of 30 to 45 minutes, three to five days per week. The physical activity should include a variety of activities, be age-appropriate and enjoyable.

Some researchers suggest schools could also promote physical activity outside physical education classes by ensuring at least 20 minutes of recess per day.

Finally, physical educators can be key drivers of physical and health literacy and behaviour change. They can do this, for example, through school-based activities and by providing information about the benefits of physical activity via newsletters and notices sent home.

Read more: Yes, your kids can run all day – they’ve got muscles like endurance athletes

Physical activity programs within schools should also address the health, mental health and stress-reduction motivations for engaging in physical activity and focus on the benefits of participation. This should include a focus on fun and enjoyment, while building confidence and independence.

Any physical activity program delivered in schools should also encourage young people to draw on parental and social support to increase the physical activity they do outside school time.

Alexandra Parker receives funding from NHMRC.

Michaela Pascoe does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.