Study reveals the limited research on ADHD treatments for adults

Attention deficit hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder. This dysfunction in brain development manifests in symptoms like distractibility and impulsiveness, which can complicate daily life for those affected. ADHD is estimated to affect 5% of children, with approximately half continuing to experience symptoms into adulthood. One of the most widely used treatments is stimulant medications, such as amphetamines or methylphenidate. However, due to a lack of investment in adult-specific clinical trials, many adult prescriptions rely on off-label use of these medications.

For example, methylphenidate, which is highly effective for treating ADHD in children, is not officially approved for adult use. “There are cases where a high school student transitioning to university cannot continue the same treatment,” says Narcís Cardoner, director of the psychiatry service at the Hospital de Sant Pau in Barcelona. “It’s absurd, yet the same drugs are used off-label because of evidence that they work in children and adolescents,” he explains. The limited number of clinical trials for adults reflects a broader issue: ADHD is still often viewed as a childhood disorder, leaving adults with few approved treatment options.

The Lancet Psychiatry published on Wednesday an analysis of 113 studies involving 14,800 participants in an effort to bridge this gap in evidence on ADHD in adults. A team led by Edoardo G. Ostinelli from the University of Oxford’s Precision Psychiatry Laboratory compared the effects of pharmacological and non-pharmacological treatments to determine what works best for adult ADHD. Their findings indicate that, in the short term, stimulants and atomoxetine — a drug that enhances focus and reduces impulsivity by increasing noradrenaline levels in the brain — are the only interventions that effectively reduce ADHD symptoms, according to both doctor and patient evaluations. However, atomoxetine was less well tolerated, with many patients discontinuing it due to side effects like increased blood pressure, headaches, and sleep problems.

The study also evaluated non-pharmacological treatments such as cognitive behavioral therapy (CBT), mindfulness, and transcranial direct current stimulation — a procedure that applies mild electrical currents to the scalp to stimulate the brain. Some of these methods showed limited efficacy, but only according to doctors’ evaluation. When patients evaluated their symptoms, no improvements were recorded.

The authors of the study describe their results as “the best available evidence base to date to inform future guidelines considering benefits and harms of available interventions for ADHD in adults.” However, they also highlight key limitations. While stimulants improved the main ADHD symptoms, such as impulsivity and difficulty concentrating, they did not significantly enhance broader measures such as overall quality of life. Additionally, the researchers argue that data is lacking on the long-term effects of these medications, as most studies focus on short-term outcomes (up to six months) due to the high cost and complexity of long-term trials.

Despite the breadth of the study, the response of experts and the very complexity of treating ADHD and related psychiatric disorders suggest that more research is needed to reach consensus on how to treat ADHD in adults. David Coghill, from the University of Melbourne, in a commentary published alongside the study, agrees that evidence-based guidelines are needed, but pointed out the difficulties of comparing drug treatments to non-drug therapies and interpreting the data from such studies.

Ashley Bush, a researcher in Psychiatry and Neuroscience at Coghill University, told SMC Australia that while non-pharmacological interventions such as psychological treatments or neurostimulation, did not alleviate the core symptoms of ADHD, “it is important to note that, in clinical practice, we treat more than the core symptoms [because] ADHD is complicated by several psychiatric disorders such as anxiety and depression.”

“It makes sense that these complications would not respond to psychostimulants as robustly,” he explained. According to Bush, while the study showed that stimulants had short-term benefits (around 12 weeks), non-pharmacological interventions may also have value in treating complications.

Cardoner agrees that, “although there is less evidence on the use of psychotherapy or neurostimulation, because it is very difficult to design trials, this does not rule out their usefulness and they should continue to be tested.”

Regarding the use of stimulants in adults, the specialist emphasizes that their application is often based more on clinical experience than on scientific studies, due to the lack of large trials for this population. “We rely on experience and on the fact that we see benefits with a very low risk,” he explains. “There are indirect measures that show that the use of psychostimulants in adults reduces substance use or accidents, which are a significant risk in these patients.”

Andrea Cipriani, director of the Oxford Precision Psychiatry Laboratory and co-author of the study, highlights the lack of “evidence of the efficacy of long-term treatments, particularly non-pharmacological options,” and underscores the importance of exploring sustainable treatment strategies that focus on enhancing the overall well-being of adults with ADHD.

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