5,515 Kids Wore Step Trackers. The Most Active Had the Best Mental Health a Year On

Parents hear plenty about screen time. Steps get less attention.

A new study suggests they deserve more.

Researchers gave 5,515 American 12-year-olds wrist trackers for three weeks. Those who walked more had fewer mental health problems a year later.

The surprise: the link didn’t level off. Every step category up the scale was linked to better mental health.

How many steps should a teenager take a day?

There’s no official step target for teenagers. Guidelines use minutes instead.

The World Health Organization recommends young people be active for at least 60 minutes a day. Worldwide, an estimated 81% of adolescents don’t reach that level, the authors note.

This study suggests a simple message for steps: more is better, at least up to 12,000 a day. The children averaged about 9,600 steps a day.

For context, adult studies have found the benefits for death risk level off at around 6,000 to 10,000 steps, depending on age. The teen mental health link showed no such ceiling.

What the research shows

Who was studied

The data came from the Adolescent Brain Cognitive Development (ABCD) Study, which follows thousands of US children from 21 sites.

Children wore Fitbit Charge 2 trackers for three weeks, around the age of 12. They also had brain scans.

A year later, the researchers measured mental health problems and school performance.

More steps, fewer problems

Higher step counts were linked to fewer mental health problems a year later. That held even after accounting for children’s earlier mental health.

The team then grouped children by daily steps and compared each group with those under 5,000 steps a day.

The differences are on a standardised scale, so they look small. What stands out is the steady climb: each band did better than the one below.

Children with 12,000 or more steps also did better than both middle groups.

What about school?

Overall, steps weren’t linked to school performance a year later.

One group stood out: children taking 10,000 to 11,999 steps scored a bit higher academically than those under 5,000.

What happened in the brain

More steps were linked to greater thickness in two parts of the brain’s outer layer, the cortex.

One, the paracentral region, is a hub for leg movement and body sensation. The other, the rostral anterior cingulate, is involved in handling conflicting information.

The researchers found that the paracentral difference statistically explained part of the link between steps and later mental health. That hints at a possible pathway, but it doesn’t prove one.

Why might walking help?

The study didn’t test causes, but the authors outline several possible routes.

Physical activity releases brain chemicals such as endorphins, dopamine and serotonin, which may ease stress. It has also been linked to lower cortisol and less inflammation, both tied to anxiety and depression.

Psychological routes may matter too, such as better self-regulation in active children.

On school results, the authors suggest everyday walking may not be enough. Brain changes linked to learning are more consistently seen with harder, moderate-to-vigorous exercise.

There’s also a brain-development angle.

The cortex naturally thins during the teen years. Thicker cortex in more active children may reflect slower thinning, though only repeated scans could show that.

How the trackers were checked

The study only counted children whose trackers gave reliable data. Each needed at least 600 minutes of valid wear a day, on at least 4 weekdays and 1 weekend day a week.

On average, children wore the tracker for about 14.6 hours a day. That makes these step counts far more trustworthy than asking children to remember how much they moved.

What earlier research found

Exercise programmes ease teen depression

A 2023 meta-analysis in JAMA Pediatrics pooled 21 trials with 2,441 children and teenagers. Physical activity programmes reduced depressive symptoms compared with control groups.

The effect was moderate, and larger in teens over 13 and those with a diagnosis.

Step benefits plateau in adults

A 2022 analysis in The Lancet Public Health pooled 15 cohorts with 47,471 adults. Risk of death fell with more steps until about 6,000 to 8,000 a day for people over 60, and 8,000 to 10,000 for younger adults.

We looked at the adult evidence in more detail in our guide to how many steps a day you need.

How it fits together

Trials show exercise can ease teen depression. This study adds everyday walking, measured objectively, and a possible brain link, in a much larger group.

How much should you trust this?

Promising. It’s large and measured steps objectively, but it can’t prove that walking caused the benefits.

What makes it convincing

• Steps were measured by trackers over three weeks, not recalled.
• A large, diverse national sample of over 5,500 children.
• A clear dose-response pattern across five step bands.
• The link held after accounting for earlier mental health.

What makes me cautious

• It’s observational; children who walk more may differ in other ways.
• Steps miss activities like swimming, cycling and many sports.
• Mental health and grades were self-reported.
• The brain-pathway analysis may overstate effects, the authors warn.
• The children studied came from more advantaged families than those left out.

What this means for you

• Every step counts. The pattern suggests any increase helps, not just reaching a magic number.
• Build walking into the day. Walking to school, errands and dog walks add up.
• Keep sport and play too. Steps miss many activities that also matter.
• Use trackers lightly. A step count can motivate, but avoid turning it into pressure.
• Watch mood, not just movement. If a child seems persistently low, talk to them and their doctor.

The CDC’s guide to physical activity for children and adolescents explains how much activity young people need and what counts.

If you’re in crisis, please contact a person, not a chatbot.

In the US, call or text 988. In the UK and Ireland, you can call Samaritans on 116 123, any time.

Elsewhere, Find a Helpline lists free services. If someone is in immediate danger, call emergency services.

In this short Mayo Clinic video, a specialist explains the health benefits when kids play sports:

What we still don’t know

1. Does walking cause the benefit? Only trials could show that.
2. Is there a ceiling? Few children took far more than 12,000 steps.
3. What about other activities? Sports and cycling weren’t captured by steps.
4. Does it last? The follow-up was one year.
5. Indoors or outdoors? The authors suggest outdoor activity may matter more, but didn’t test it.

My take: steps are an easy win

What I like about this study is how simple and measurable its message is. No gym, no equipment, just more walking.

I’m less convinced by headlines claiming walking “builds teen brains”. The brain findings are correlations and small.

But the pattern is steady, and it lines up with trials showing exercise eases teen depression. Walking is cheap, safe and good for plenty of other things too.

If I were a parent, I’d make walking part of the day, not a target to hit.