RESEARCH
Research
ADHD (Attention Deficit Hyperactivity Disorder)
has been the subject of extensive research over the years, leading to many seminal studies and breakthroughs. Below, are a few key studies that have significantly contributed to our understanding of ADHD:
The Multimodal Treatment Study of Children with ADHD (MTA Study) - Arnold, L.E., Abikoff, H.B., Cantwell, D.P., Conners Archives of General Psychiatry, 1997
This is one of the most influential and long-running studies on ADHD. It began in the 1990s and compared the effectiveness of various treatments, including medication, behavioural therapy, and a combination of both. The MTA study provided critical insights into the management of ADHD and the importance of multimodal treatments.
The National Institute of Mental Health (NIMH) Multimodal Treatment Study of ADHD Follow-up (MTA-2) – MTA Cooperative Group, Paediatrics, 2004.
This long-term follow-up study of the original MTA Study tracked children with ADHD into adolescence and adulthood. It provided valuable insights into the long-term outcomes of various ADHD treatments, including the role of medication in managing symptoms in the long term.
The International Multicentre ADHD Genetics (IMAGE) Project - Kuntsi, J., Neale, B.M., Chen. The IMAGE project: methodological issues for the molecular genetic analysis of ADHD. Behavioral and Brain Functions, 2006)
This project aimed to identify genes associated with ADHD. It involved a large-scale collaboration among researchers from around the world. While ADHD has a complex genetic basis, this research has helped identify several genes linked to the disorder, shedding light on its hereditary aspects.
The Preschool ADHD Treatment Study (PATS) - Kollins, S., Greenhill, L., Swanson, J., Wigal. Rationale, design, and methods of the Preschool ADHD Treatment Study (PATS). Journal of the American Academy of Child & Adolescent Psychiatry, 2006).
This study focused on early intervention for preschool-aged children with ADHD. It investigated the effectiveness of medication (methylphenidate) and behavioural therapy in young children, highlighting the importance of early diagnosis and treatment.
Neuroimaging Studies such as the ABCD study (Wang, Z., Zhou, X., Gui, Y., Liu, M. and Lu, H., 2023. Multiple measurement analysis of resting-state fMRI for ADHD classification in adolescent brain from the ABCD study. Translational Psychiatry, 13(1), p.45)
have revealed structural and functional differences in the brains of individuals with ADHD, particularly in regions related to attention and impulse control.
Meta-Analyses:
Several meta-analyses have synthesized data from multiple studies to provide a comprehensive view of the origins, risk factors effectiveness of ADHD treatments, such as medication and behavioural interventions. These analyses have helped inform clinical guidelines for managing ADHD.
ADHD in Adulthoods:
Research on ADHD has expanded to focus on its presentation and management in adults. Studies have explored the persistence of ADHD symptoms into adulthood and the challenges faced by adults with ADHD in various life domains. Notably a meta-analysis by Song et al. (2021) calculated the prevalence of persistent adult ADHD (from childhood) was 2.58% and that of symptomatic adult ADHD (without childhood origin) was 6.76%, translating to 139.84 million and 366.33 million affected adults in 2020 globally.
Other Treatment Research:
Stimulants are often prescribed to help people with ADHD focus their thoughts. But what is going on in the brain that can explain improvements in concentration?
A seminal study by Mitul et al., (2000) called ‘Methylphenidate Enhances Working Memory by Modulating Discrete Frontal and Parietal Lobe Regions in the Human Brain’ The Journal of Neuroscience, 2000, Vol. 20 RC65 1 of 6). Working memory (immediate memory) is the brain function that allows the person to manipulate and process immediate sensory and language based information. Using an early version of Token Search (a working memory cognitive test), Mitul et Al (2000) were one of the first to demonstrate that methylphenidate (Ritalin) improves working memory. Earlier, in 1999, a team of researchers at University of Cambridge, had neurotypical (unaffected) participants complete a task during PET brain imaging. Half the participants were given methylphenidate, and the other half were given a placebo.
Performance was improved by the stimulant (Ritalin): the treatment group made fewer errors on the working memory task, especially if they were impaired to begin with. That’s not surprising given the above, but this study went a step further and examined activity in the brain regions previously shown to be associated with this task, such as the dorsolateral prefrontal cortex and posterior parietal cortex. Here are results for the latter:
On an easy control activity, not much was going on in this region of the brain, regardless of whether participants were on the drug or not. But during the Token Search task, there was a lot less activity in this region of the brains of participants who took methylphenidate.
Why less activity?
The researchers speculate it may be due to increased efficiency of the brain network supporting working memory performance, perhaps because distracting information is not processed. More is not always better when it comes to the brain, and especially when it comes to attention.
Most practitioners can’t do a brain scan for every patient concerned with ADHD, but at Neuromed clinic we can perform an EEG scan to see how your brain is functioning and we can also use the Token Search task to measure deficits in performance and to help identify patients who may benefit from clinical intervention.
