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.
In a recent study, researchers delved into the complex interplay of cognitive processes and eye movements in children with dyslexia and Attention-Deficit/Hyperactivity Disorder. Their findings shed light on predictive models for reading outcomes in these children compared to typical readers.
The study involved 59 children: 19 typical readers, 21 with ADHD, and 19 with developmental dyslexia (DD), all in the 4th grade and around 9 years old on average. Each group underwent thorough neuropsychological and linguistic assessments to understand their psycholinguistic profiles.
During the study, participants engaged in a silent reading task where the text underwent lexical manipulation. Researchers then analyzed eye movement data alongside cognitive factors like memory, attention, and visual processes.
Using multinomial logistic regression, the researchers evaluated predictive models based on three key measures: a linguistic model focusing on phonological awareness, rapid naming, and reading fluency; a cognitive neuropsychological model incorporating memory, attention, and visual processes; and an additive model combining lexical word properties with eye-tracking data, specifically examining word frequency and length effects.
By integrating eye movement data with cognitive factors, the researchers enhanced their ability to predict the development of dyslexia or ADHD, in comparison to typically developing readers. This approach significantly improved the accuracy of predicting reading outcomes in children with learning disabilities.
These findings have profound implications for understanding and addressing reading challenges in children. By considering both cognitive processes and eye movement patterns, educators and clinicians can develop more effective interventions tailored to the specific needs of children with dyslexia and ADHD.
The Study Setup
The researchers recruited children aged 6-12 years diagnosed with ASD and/or ADHD, along with their non-ASD/ADHD siblings and the unrelated non-ASD/ADHD volunteers. The diagnoses were confirmed using standardized assessments like the Autism Diagnostic Observation Schedule-2 (ADOS-2). The study looked at gut microbial diversity using advanced DNA extraction and sequencing techniques, comparing alpha-diversity indices (which reflect the variety and evenness of microbial species within each gut sample) across different groups. They also assessed dietary diversity through standardized questionnaires.
Key Findings
The study included 98 subjects, comprising children with ASD, ADHD, both ASD and ADHD, their non-ASD/ADHD siblings, and the unrelated controls. Here's what they discovered:
What Does This Mean?
The study highlights intriguing connections between gut microbiota and neurodevelopmental disorders like ASD and ADHD. The lower gut microbial diversity observed in children with ASD points towards potential links between gut health and the pathophysiology of ASD. Understanding these connections is crucial for developing targeted therapeutic interventions.
Implications and Future Directions
This research underscores the importance of considering gut microbiota in the context of neurodevelopmental disorders. Moving forward, future studies should account for factors like co-occurrence of ASD and ADHD, as well as carefully control for dietary influences. This will help unravel the complex interplay between gut microbiota, diet, and neurodevelopmental disorders, paving the way for innovative treatments and interventions.
In summary, studies like this shed light on the intricate relationship between our gut health, diet, and brain function. By unraveling these connections, researchers are opening new avenues for understanding and potentially treating conditions like ASD and ADHD.
A commonly reported risk associated with ADHD medication is reduced growth in height. But studies to date have generally not adequately described or measured possible confounders, such as genetic factors, prenatal factors, or socioeconomic factors. What if ADHD were associated with reduced height even in the absence of medications?
An international study team explored this question by performing a nationwide population study comparing data from before (1968-1991) and after (1992-2020) the adoption of stimulant therapy for ADHD in Sweden.
The country’s single-payer health insurance system that connects patient records with all other national registers through unique personal identification numbers makes such analysis possible. Sweden also has military service conscription, which records the heights of 18-year-old males.
The participants were all 14,268 Swedish males with a diagnosis of ADHD who were drafted into military service at any time from 1968 through 2020.
Up to five non-ADHD controls were identified for each ADHD case, matched by sex (they had to be male), birth year, and county. The total number of controls was 71,339.
Among 34,586 participants in the period before adoption of stimulant medications (1968-1991), those diagnosed with ADHD had roughly 30% greater odds of being shorter than normal (166-172 vs. 173-185 cm) than typically developing controls. That dropped to 20% greater odds among the 34,714 participants in the cohort following adoption of stimulant medications.
The odds of those diagnosed with ADHD being much shorter than normal (150-165 vs. 173-185 cm) remained identical (about 55% greater) among the almost 30,000 participants in both cohorts.
In other words, there was no increase in the odds of ADHD individuals being shorter than normal after adoption of stimulant therapy in Sweden compared with before such adoption.
Furthermore, after adjusting for known confounders, including birth weight, inflammatory bowel disease, celiac disease, hypothyroidism, anxiety disorders, depression, substance use disorder, and highest parental education, the odds of those diagnosed with ADHD being shorter than normal or much shorter than normal in the 1992-2020 cohort dropped to roughly 10% and 30% greater, respectively.
Could it be the disorder itself rather than stimulant treatment that is associated with reduced height in individuals diagnosed with ADHD?
To address effects of environmental and familial/genetic confounding, the team then compared the entire cohort of males diagnosed with ADHD from 1968 through 2020 with typically developing male relatives, ranging from first cousins to full siblings.
Among full siblings, the odds of those with ADHD diagnoses being shorter (over 90,000 participants) or much shorter (over 77,000 participants) were a statistically significant 14% and 18%, respectively.
The authors concluded, “Our findings suggest that ADHD is associated with shorter height. On a population level, this association was present both before and after ADHD-medications were available in Sweden. The association between ADHD and height was partly explained by prenatal factors, psychiatric comorbidity, low SES [socioeconomic status] and a shared familial liability for ADHD.”
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