One in five children starting methylphenidate dropped 10 or more weight centiles within three months

Design

Retrospective multicentre cohort using a common data model (Korea, 2008–2024)

Population

2,087 children and adolescents aged 3–18 starting methylphenidate

Primary outcome

Change in weight and weight centile within 3 months

Effect

−0.33 kg (95% CI −0.44 to −0.22); −2.49 centiles; ≥10-centile fall in 21.6% (28.6% preschool)

This retrospective study used a Korean common data model covering 17 hospitals from 2008 to 2024. It included 2,087 children and adolescents aged 3 to 18 who started methylphenidate and had weight recorded before and within 90 days after starting (69% male, 58% aged 6 to 10).

Within three months, mean weight fell by 0.33 kg (95% CI 0.22 to 0.44) and 2.49 centiles (2.15 to 2.83). Overall, 21.6% dropped 10 or more centiles, and in preschool children the figure was 28.6%.

In July 2025 the FDA warned of significant weight loss in young children taking stimulants for ADHD. This study gives a real-world size to that risk. The mechanism is appetite suppression, usually worst at midday, and it can be managed by dose timing, meal planning and monitoring.

• Weigh every child before starting methylphenidate and again within the first three months.
• Plot weight on a growth chart; a drop of 10 or more centiles warrants review of dose and diet.
• Take extra care in preschool children, who lost weight most often; methylphenidate is not licensed under 6 years in many countries.
• Encourage a good breakfast before the dose and an evening meal or snack when appetite returns.
• Continue monitoring height and weight at least every six months during treatment.

Why it matters

It turns a regulatory warning into a monitoring schedule a prescriber can follow.

Don't overread it

This is an uncontrolled retrospective study; it measures weight change, not long-term growth or health effects.

The statistics, in plain English

A mean loss of 0.33 kg sounds trivial, but averages hide the one in five who fell sharply. Children without follow-up weight data were excluded, which could bias the estimate in either direction. There was no comparison group of untreated children.

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