March 15, 2024
There is increasing interest in digital interventions to treat ADHD symptoms and to overcome deficits in executive functioning that are associated with this disorder. Executive functions such as working memory and cognitive speed originate in the frontal lobes of the brain, and guide voluntary goal-directed behavior. They affect reading speed and accuracy, reading comprehension, attention, and impulse control, among other behaviors important to the ability to function in social, educational, and professional environments.
A Swedish study team based at Umeå University recently conducted a systematic search of the medical literature to explore the efficacy of computerized cognitive training (CCT) to improve executive functioning in adults with ADHD.
They included published randomized controlled trials (RCTs) involving adults 18 to 65 years old with a primary diagnosis of ADHD. The controls were participants with either a passive (wait-list) or active (modified simple training) intervention.
Nine RCTs with a combined total of 285 participants met inclusion criteria. Lumping together all cognitive outcome types, meta-analysis reported a small effect size improvement that was just barely statistically significant (p = .048, with p < .05 as the boundary).
However, when separated out by individual outcome types – executive functioning, cognitive speed, general short-term memory, or ADHD symptom severity – the meta-analyses found no improvements that reached statistical significance.
Moreover, all RCTs except one were judged as high risk of bias.
While it is possible that additional studies enlarging the pool of participants could lead to statistical significance, all effect sizes were small to begin with, which is not encouraging.
The team concluded, “Considering the small positive effect in this meta-analysis for overall cognitive outcomes, together with the lack of evidence for far transfer, practitioners and individuals with ADHD should weigh the costs (resources and time) against the benefits of training.”
A South Korean study team recently concluded the first RCT-only meta-analysis of game-based digital therapeutics (DTx).
Combining 14 RCTs with a total of 1,183 participants, they found a small effect size improvement in parent-rated attention symptoms for game-based DTx interventions over controls. Nine RCTs combining 424 participants likewise found a small effect size improvement in teacher-rated attention symptoms. Between-study variation (heterogeneity) was negligible, and there was no indication of publication bias.
Combining five RCTs with a total of 256 participants, they reported small effect size improvements in both parent and teacher-rated hyperactivity/impulsivity symptoms. But they found no improvement in hyperactivity symptoms alone, whether evaluated by parents or teachers. Heterogeneity was in all instances negligible, with no sign of publication bias.
The team then compared game-based DTx interventions with pharmaceutical treatment.
ADHD medications outperformed game-based DTx interventions for improvement of attention symptoms in both parent (four RCTs with a total of 128 participants) and teacher (three RCTs with 92 participants) ratings, with small-to-medium effect sizes. Medications likewise prevailed in improving hyperactivity/impulsivity symptoms, whether rated by parents or teachers, with small-to-medium effect sizes.
The team concluded, “This study is the first direct and indirect meta-analysis to compare the efficacy of game-based DTx between control and medication according to the assessor in an RCT. In conclusion, game-based DTx had a more significant effect than the control. Additionally, between medication treatment versus DTx, medication was more effective.”
Pia Elbe, Christian Bäcklund, Mariana Vega-Mendoza, Daniel Sörman, Hanna Malmberg Gavelin, Lars Nyberg, and Jessica K. Ljungberg, “Computerized Cognitive Interventions for Adults With ADHD: A Systematic Review and Meta-Analysis,” Neuropsychology (2023), https://doi.org/10.1037/neu0000890.
SuA Oh, Jina Choi, Doug Hyun Han, and EunYoung Kim, “Effects of game-based digital therapeutics on attention deficit hyperactivity disorder in children and adolescents as assessed by parents or teachers: a systematic review and meta-analysis,” European Child & Adolescent Psychiatry (2023), https://doi.org/10.1007/s00787-023-02174-z.
Background
ADHD (Attention-Deficit/Hyperactivity Disorder) is one of the most studied neurodevelopmental conditions, with many clinical trials evaluating the effectiveness and safety of various medications. These trials, known as randomized controlled trials (RCTs), are considered the gold standard for assessing treatments. However, strict eligibility criteria often exclude many real-world patients, raising questions about whether the findings from these trials apply to everyday clinical settings.
Our latest study sheds light on this issue, revealing just how many individuals with ADHD might be excluded from RCTs and the impact this exclusion has on their treatment outcomes.
Method
Researchers used Swedish national registries to analyze data from 189,699 individuals diagnosed with ADHD who started medication between 2007 and 2019. They applied exclusion criteria from 164 international RCTs to identify who would have been considered ineligible for these trials in order to determine the proportion of individuals with ADHD who would not meet the eligibility criteria for RCTs.
Key Findings
Many Patients Are Ineligible for Clinical Trials:
Ineligible Patients Face Unique Challenges:
Higher Risk of Adverse Outcomes:
What This Means
These findings highlight a major gap between the controlled environments of clinical trials and the realities faced by individuals with ADHD in everyday life. While RCTs provide valuable insights, their restrictive criteria often exclude patients with more complex health profiles or co-existing conditions. This limits the generalisability of trial results, meaning that treatment guidelines based solely on RCTs may not fully address the needs of all patients.
Conclusion
This study demonstrated that a significant proportion of individuals with ADHD, particularly adults, do not meet the eligibility criteria for standard RCTs. These results emphasize the importance of bridging the gap between research settings and real-world applications. By recognizing and addressing the limitations of RCTs, we can work towards more equitable and effective ADHD treatment strategies for everyone.
Background:
Our understanding of Attention-deficit/hyperactivity disorder (ADHD) has grown and evolved considerably since it first appeared in the DSM-II as “Hyperkinetic Reaction of Childhood.” This study aimed to find the disorder’s placement within the modern psychopathology classification systems like the Hierarchical Taxonomy Of Psychopathology (HiTOP).
The HiTOP model aims to address limitations of traditional classification systems for mental illness, such as the DSM-5 and ICD-10, by organizing psychopathology according to evidence from research on observable patterns of mental health problems.. Is ADHD best categorized under externalizing conditions, neurodevelopmental disorders, or something else entirely? A recent study by Zheyue Peng, Kasey Stanton, Beatriz Dominguez-Alvarez, and Ashley L. Watts takes a closer look at this question using a symptom-focused approach.
The Study:
Traditionally, ADHD has been associated with externalizing behaviors, such as impulsivity and hyperactivity, or with neurodevelopmental traits, like cognitive delays. However, this study challenges the idea of placing ADHD into a single category. Instead, it maps ADHD symptoms across three major psychopathology spectra: externalizing, neurodevelopmental, and internalizing.
The findings reveal that ADHD symptoms don’t fit neatly into one box. For example, symptoms like impulsivity, poor school performance, and low perseverance were strongly associated with externalizing behaviors. On the other hand, cognitive disengagement (e.g., daydreaming, blank staring) and immaturity were closely linked to neurodevelopmental challenges. Interestingly, cognitive disengagement also showed ties to internalizing symptoms, such as anxiety or depression.
This research underscores the complexity of ADHD. Rather than treating ADHD as a single, unitary construct, the study advocates for a symptom-based approach to better understand and treat individuals. By acknowledging that ADHD symptoms relate to multiple psychopathology spectra, clinicians and researchers can move toward more nuanced classification systems and targeted interventions.
Conclusion:
Ultimately, this study highlights the need for modern systems to move beyond rigid categories and adopt a more flexible, symptom-focused framework for understanding ADHD’s place in psychopathology.
Exposure to heavy metals like lead, arsenic, mercury, cadmium, and manganese is known to harm developing nervous systems. However, past studies on whether heavy metals specifically increase the risk of ADHD have shown mixed results.
A research team from China (Gu et al., 2024) reviewed medical studies and conducted meta-analyses to better understand this issue.
The team included studies on children and teens, focusing on cohort studies, case-control studies, and cross-sectional studies. They only used articles written in English and required validated biomonitoring (like blood tests) to measure heavy metal exposure. ADHD diagnoses had to come from clinical evaluations.
To be included, studies had to report effect sizes such as odds ratios and relative risks with confidence intervals. The team focused on comparisons between groups with high, low, or no exposure, which made it harder to analyze dose-response relationships.
They also evaluated the quality of each study. All cohort studies were rated high-quality. Of the 15 case-control studies, 6 were high-quality, and 9 were moderate-quality. Among cross-sectional studies, only 2 were high-quality, and the rest were moderate-quality.
There was no evidence linking ADHD to other heavy metals like arsenic, mercury, cadmium, or manganese. Both meta-analyses suggest that lead exposure is associated with the risk for ADHD. However, because these studies cannot rule out other explanations, one cannot conclude that lead exposure causes ADHD. For example, other work shows that people with ADHD are likely to have lower incomes than those without ADHD.
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