July 30, 2021
A team of Iranian researchers recently published a meta-analysis seeking to determine what, if any, association there may be between low vitamin D levels and ADHD in children and adolescents.
Combining the results from thirteen studies with 10,334participants, they found that youth with ADHD had "modest but significant" lower serum concentrations of 25-hydroxyvitamin D than normally developing children. The weighted mean difference was just under 7 nanograms per milliliter. The odds of obtaining such a result by chance would be less than one in a thousand(p < .001). There was little to no sign of publication bias. Between-study heterogeneity, however, was very high (I2 = 94).
These results suggest an association. But are low serum levels of vitamin D a cause or effect of ADHD? Causation is vastly more difficult to establish than an association. To begin to tease this out, the researchers identified four prospective studies that compared maternal vitamin D levels with the subsequent development of ADHD symptoms in their children. Two of these used maternal serum levels, and two used umbilical cord serum levels. Together, these studies found that low maternal vitamin D levels were associated with a 40% higher risk of ADHD in their children. Whether maternal serum or umbilical cord serum measurements were used had little or no effect on the outcome. Study heterogeneity was negligible. But the authors noted that this result "should be considered with caution" because it was heavily dependent on one of the prospective studies included in the analysis. All of which suggest a need for further prospective studies
In the meantime, the authors suggest it would be prudent to increase sun exposure and vitamin D supplementation, given the prevalence of vitamin D deficiency.
YadollahKhoshbakht, Reza Bidaki, and Amin Salehi-Abargouei, "Vitamin D Status and Attention Deficit Hyperactivity Disorder: A systematic review and Meta-Analysis of Observational Studies," Advances in Nutrition, vol. 9, issue 1, p. 9-20(2018).
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.
The Background:
Caffeine and its primary breakdown compounds – paraxanthine, theophylline, and theobromine (also the primary alkaloid in chocolate) – readily cross the placenta and tend to linger due to the underdevelopment of fetal caffeine metabolizing enzymes.
Could accumulating caffeine metabolites harm the developing fetal brain? Studies to date have come to contradictory conclusions, some finding an association, others finding none.
Norway has a national single-payer health insurance system with a national health registry comprehensively tracking virtually all residents.
The Methods:
An international study team used Norways’s registry, and its Mother, Father, and Child Cohort Study (MoBa) to explore the relationship between maternal and paternal coffee consumption and offspring neurodevelopmental difficulties (ND), including symptoms of ADHD as determined from validated rating scales, using 58,964 mother-child pairs and 22,576 father-child pairs, covering the decade 1999-2008.
Unadjusted results indicated a strong association between maternal coffee consumption before and during pregnancy with offspring ADHD, but none with paternal coffee consumption. Superficially, that might seem like compelling evidence.
Yet after adjusting for education, income, smoking, and alcohol, “previously significant effects attenuated towards zero and some associations switched from being positive to negative.”
Then, after further adjusting for genetic confounding, ADHD symptoms at 1.5 years, 3 years, 5 years (on both of two different rating scales), and 8 years (including separate measures of inattention and hyperactivity symptoms) all became indistinguishable between offspring from mothers consuming coffee during pregnancy and offspring of mothers abstaining from coffee during pregnancy.
Conclusion:
The team concluded, “This study applied several conventional and genetic epidemiological approaches to investigate the potential relationship between maternal coffee consumption during pregnancy and offspring NDs [neurodevelopmental difficulties]. When considering the results of the conventional and genetic epidemiological analyses, as well as the broader literature, we conclude that there is little evidence that maternal coffee consumption during pregnancy is strongly causally related to offspring NDs.”
More specifically, the team found no evidence of any causal relationship with offspring ADHD.
_logo%201.svg)
