Findings should help inform clinical practice and the debate on ADHD drug treatment
Drug treatment for people with newly diagnosed attention deficit hyperactivity disorder (ADHD) is associated with significantly reduced risks of suicidal behaviours, substance misuse, transport accidents, and criminality, finds a study published by The BMJ today.
The researchers say this is the first study of its kind to show beneficial effects of ADHD drug treatment on broader clinical outcomes for all ADHD patients and should help inform clinical practice.
ADHD affects around 5% of children and 2.5% of adults worldwide and is associated with adverse outcomes including suicidal behaviours, substance misuse, accidental injuries, transport accidents and criminality.
Although randomised trials have shown that ADHD medication alleviates core symptoms, evidence of its effects on these broader clinical outcomes are more limited.
To address this knowledge gap, researchers drew on data from Swedish national registers (2007-2020) to examine the effects of ADHD drug treatment in 148,581 individuals aged 6-64 years with a new diagnosis of ADHD.
Using a technique called target trial emulation, which applies the design principles of randomised trials to observational data, they assessed first and recurrent events for five outcomes (suicidal behaviours, substance misuse, accidental injuries, transport accidents, and criminality) over two years after diagnosis.
Of the 148,581 individuals with ADHD (average age 17 years; 41% female), 84,282 (57%) started drug treatment for ADHD, with methylphenidate being the most commonly prescribed (88.4%).
After accounting for factors including age, sex, education level, psychiatric diagnoses and medical history, ADHD medication was associated with reduced rates of a first occurrence of four of the five outcomes: a 17% reduction for suicidal behaviour, 15% for substance misuse, 12% for transport accidents, and 13% for criminality.
The reduction was not statistically significant for a first-time accidental injury (88.5 v 90 per 1000 person years).
However, amongst people with recurrent events, the rate reductions associated with ADHD medication were seen for all five outcomes: a 15% reduction for suicidal attempts, 25% for substance misuse, 4% for accidental injuries, 16% for transport accidents, and 25% for criminality.
Possible explanations include reduced impulsivity, which might lower criminality by curbing aggressive behaviour, and enhanced attention, which might decrease the risk of transport accidents by minimising distractions, suggest the authors.
They acknowledge several limitations, such as being unable to assess data on non-drug treatments or the impact of drug dosage. And while target trial emulation is one of the most rigorous approaches for analysing observational data, they can't rule out the possibility that other factors, such as ADHD severity, genetic predispositions, and lifestyle factors, may have affected their results, so no definitive causal conclusions can be drawn.
However, this was a large study based on national registry data and findings were similar after further sensitivity analyses, suggesting they are relevant to people with ADHD in real-world clinical settings.
As such, they conclude: "These results provide evidence on the effects of ADHD drug treatment on important health related and social outcomes that should inform clinical practice and the debate on the drug treatment of ADHD."
