The largest study of its kind has revealed that medication for attention-deficit/hyperactivity disorder (ADHD) has a real-world social impact – for both those taking the drugs and others in the community. Looking at the data of nearly 150,000 newly diagnosed, researchers say the medications have sweeping benefits beyond managing symptoms of the condition.
Researchers from Sweden's Karolinska Institutet investigated the data of 148,581 people aged 6-64 years (mean age 17 years and 41% female), newly diagnosed with ADHD between 2007 and 2018. More than half (56.7%) began taking medication within three months of their diagnosis, with the drug most commonly prescribed being the stimulant methylphenidate, or Ritalin or Concerta (88.4%). The team was interested in assessing the medication's impact, over two years (2018 to 2020), on five specific outcomes: Suicidal behaviors, substance abuse, accidental injuries, transport accidents and criminal convictions.
While an observational study, the researchers used a technique known as "target trial emulation," where the design and analysis of real-world health data are made to mimic a clinical trial as closely as possible – without actually running one. This approach helps scientists compare groups more fairly and identify likely cause-and-effect relationships, rather than just spotting associations.
The researchers found that, for those taking medication, the rate of a first suicide attempt or other suicidal behavior was 17% lower than in self-managed ADHD individuals. Substance misuse was down 15%, transport accidents 12% and criminal convictions 13%. The rate of accidental injuries, however, was all but unchanged.
"This study shows that individuals who started ADHD medication showed a reduction in suicidality, substance misuse and criminality," said Adam Guastella, a professor at The University of Sydney, who wasn't involved in the study but whose work centers on youth neurodevelopmental research. "Such benefits have been shown repeatedly in previous studies, but the large sample size, use of a national registry, and more sophisticated analysis give greater confidence in these results that the findings aren't explained by something other than medication use."
And when the researchers looked at people who experienced these outcomes more than once, things shifted even more dramatically. Medication was linked with fewer repeat episodes across the five outcomes, including a small but statistically significant drop in injuries. There was a 15% reduction in suicidal attempts, a 25% drop in substance misuse, 4% fewer accidental injuries, 16% fewer transport accidents, and criminal convictions were down 25%.
"This research provides further evidence that stimulant medication treatments for ADHD can be life changing, reducing the risk of individuals experiencing a motor vehicle accident and drug-related harms, in addition to reducing the likelihood that they will engage in criminal behavior and suicide," said Stephen Bright, a senior lecturer specializing in addiction at Edith Cowan University's School of Medical and Health Sciences in Australia, who was not part of the research team.
Looking into the demographics, adults had a greater reductions in substance misuse and criminality than children and young people – which may not be that surprising – however, women experienced a stronger fall in first-time criminal convictions than men. The crime statistics were sourced from Sweden's National Crime Register and covered anyone who had been convicted of any crime, from minor property convictions to violent offenses.
In a smaller study dating back to 2012, researchers from the same institution conducted some of the earliest research on ADHD medication and crime, finding that among more than 25,000 Swedes, there was a significant reduction in criminal behavior for individuals taking some form of drug for the condition.
The researchers suggest that these statistics may be a result of many factors – better impulsivity control could mean less aggressive behavior, so a lower rate of criminality, and improved attention might lower the risk of mishaps like personal injuries and transport accidents.
There's another interesting aspect to the way this latest large population study was designed. In a normal clinical trial, participants would be randomly assigned to take a drug or not, so the two groups should be similar in every way except for the treatment. However, in an observational study like this, there are factors that are harder to control for – such as ADHD severity, healthcare access and different approaches by medical professionals. To make the comparison as fair as possible, the researchers created two virtual versions of each person in the data – one assigned to the “medication” group and one to the “no medication” group – and tracked what they did in real life. If the real-world actions didn’t match their assigned group, that version was dropped. They then adjusted for dozens of factors, from age and sex to medical history, to make the groups as similar as possible.
Of course, target trial emulation design doesn’t remove all the uncertainty, but it does reduce many of the biases that are inherent with observational studies.
Nonetheless, there were still limitations here. The researchers focused specifically on drug intervention for ADHD in general and didn't factor in type of medication or dosage. Nor did it look at other kinds of treatments available, such as behavioral therapy. And even after adjusting the data for common variables, there are still unknown influences – including genetics, healthcare access and ADHD severity. So no causal relationships can be confirmed, despite the robustness of the research. In addition to this, it was purely Sweden-based.
"The main concern is that the authors do not take account of the healthy user bias – only patients compliant for two years are included in the medicated arm," said Professor Jon Jureidini, a child psychologist and researcher at The University of Adelaide. "Patients who comply with treatment, especially for such a long period, are not representative of the medicated population. They and their families are more likely to engage in a broad spectrum of behaviors consistent with a healthy lifestyle. Outcomes for those who were non-compliant should also have been analyzed, even if only as a secondary analysis to acknowledge the possibility of healthy user bias."
Still, the scale and design of the study make it one of the most comprehensive attempts yet to quantify the real-world impact of ADHD drugs. And it offers a solid guide for patients, families and medical professionals when it comes to deciding whether therapeutic intervention is likely to benefit someone based on their individual circumstances and background – particularly when it comes to the study's five measured real-world outcomes.
"While there are concerns about the over-prescribing of stimulant medications," added Bright, "it is important that we find the right balance between protecting the community from diverted medications and the right of people with ADHD to access a gold standard treatment so that they are able to thrive and be productive members of society."
The study does make a case for how access to medication has the potential to benefit both the person living with ADHD and the broader community. This is an important aspect, considering that there is ongoing debate about whether the condition has become over-diagnosed and that stimulants can be misused – both arguments have been repeatedly debunked, but it's something that still divides medical professionals.
“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," the researchers concluded.
The study was published in the journal BMJ.
Source: Karolinska Institutet via Scimex
