June 12, 2021

Is there an association between asthma and ADHD?

An international team of researchers has carefully examined the best current evidence and found strong evidence for an association between asthma and ADHD by combining a meta-analysis of prior data with a new analysis of the Swedish population.

The meta-analysis identified 46 datasets with a total of more than 3.3 million persons.  It computed an unadjusted (odds)'s ratio (OR) of 1.7, which indicates that ADHD patients have about twice the risk of developing asthma compared with people without ADHD. Limiting the meta-analysis to studies that adjusted for confounding factors, 30 datasets with more than a third of a million participants still led to an adjusted (odds)' ratio of 1.5 (95% CI 1.4 - 1.7). The likelihood of obtaining this result by chance in such a large sample would be less than one in ten thousand.

When the team further checked this result against the results for the Swedish population of more than one and a half million persons, the (odds)  ratio was almost identical to 1.6. Adjusting for confounding factors reduced it to 1.5 (95% CI 1.41 - 1.48). That means the findings are very robust: asthma and ADHD are associated, with an (odds)'ratio of 1.5, after adjusting for confounding factors.

What does this small but statistically very reliable association between asthma and ADHD mean? For researchers, it suggests that the two disorders may have common risk factors and that the search for these shared risk factors might lead to improved treatments.  These risk factors might also be shared with two other somatic conditions for which ADHD patients are at increased risk: obesity and eczema.  Common inflammatory processes may account for this overlap among disorders.  Clinicians should be aware that children with asthma have an increased risk for ADHD, although, given the small association, systematic screening may not be warranted.  But given that ADHD might interfere with asthma medication compliance, the disorder should be considered among noncompliant youth, especially among those who show other evidence of inattention, poor memory, or disorganization.

Samuele Cortese, Shihua Sun, Junhua Zhang, Esha Sharma,Zheng Chang, Ralf Kuja-Halkola, Catarina Almqvist, Henrik Larsson, Stephen VFaraone, "Association between attention deficit hyperactivity disorder andasthma: a systematic review and meta-analysis and a Swedish population-basedstudy," Lancet Psychiatry, Published online July 24, 2018 http://dx.doi.org/10.1016/S2215-0366(18)30224-4.

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Meta-analysis finds little to no association between prenatal cannabis exposure and offspring ADHD

Meta-analysis Finds Little-to-No Association Between Prenatal Cannabis Exposure and Offspring ADHD

Prevalence of cannabis use among pregnant women is on the rise with the spread of legalization. The most frequently reported reasons for use are to relieve stress or anxiety, nausea or vomiting, pain, and for recreation.

Given that the primary psychoactive ingredient of cannabis, ∆9-tetrahydrocannabinol (THC) is a small fat-soluble molecule that can easily cross the placenta, an Israeli-U.S. research team conducted a systematic search of the peer-reviewed medical literature for studies exploring possible neuropsychiatric effects on offspring.  

They included not only studies evaluating likelihood of ADHD, but also autism spectrum disorder, anxiety, depression, and psychotic symptoms. For each of these, adjustment was made for known confounding variables.

With that adjustment, meta-analysis of six studies with a total of over half a million (503,661) participants reported a 13% increase in the odds of ADHD in offspring of mothers using cannabis during pregnancy compared with offspring of mothers not using cannabis while pregnant.

That is generally considered a small effect size increase in risk. But there are multiple reasons to question even this minimal finding:

  • It barely achieved statistical significance.
  • A few studies used more reliable clinical diagnoses, while most just used ADHD symptom rating scales.
  • It is virtually impossible to eliminate all confounding variables. Twin studies come closest to fully accounting for otherwise unmeasured environmental and genetic confounders, but no such studies were included.
  • The team made no effort to evaluate publication bias.  
  • Almost all the participants (497,821) were in a single study, and that study – which relied on clinical diagnoses – did not find a significant association.

Meta-analysis of two studies with a total of 741 individuals reported a 20% increase in offspring use of cannabis among mothers who used cannabis during pregnancy, but once again this was subject to methodological shortcomings:

  • Two studies do not make for a robust meta-analysis, even more so with only 741 participants.
  • The result barely achieved statistical significance.
  • Publication bias was unaddressed.
  • Small effect sizes are questionable due to the virtual impossibility of eliminating all confounding variables, especially without twin studies.

Some studies have suggested a link between cannabis and psychotic symptoms. But meta-analysis of four studies combining over nineteen thousand persons found no significant association between maternal cannabis use during pregnancy and offspring psychotic symptoms.

Many studies have pointed to commonalities in the etiology of ADHD and autism spectrum disorder (ASD). Yet meta-analysis of five studies encompassing over half a million participants found absolutely no association between maternal prenatal cannabis use and ASD.  

The remaining meta-analyses also reported no association with depression or anxiety.

With the caution that absence of evidence is not the same as evidence of absence, it is by no means clear from what is presently known that prenatal cannabis exposure has any significant neuropsychiatric effects on offspring. And if further research finds any effects, they are likely to be minor.

July 26, 2024

Meta-analysis Associates Dasotraline with Some Reduction in ADHD Symptoms

Meta-analysis Associates Dasotraline with Some Reduction in ADHD Symptoms

Dasotraline is a serotonin-norepinephrine-dopamine reuptake inhibitor (SNDRI) that had been under development by Sunovion for treating ADHD and binge eating disorder.  

An Indian research team conducted a systematic search of the peer-reviewed medical literature to perform meta-analyses of the quantitative outcomes of clinical trials. 

Meta-analysis of five double-blinded randomized clinical trials (RCTs) with a combined total of 1,498 participants reported a small-to-medium effect size reduction in ADHD symptoms in patients given dasotraline as opposed to those given placebo. 

There were, however, strong indications of publication bias. Using the trim-and-fill procedure to correct for that bias yielded a small effect size reduction in ADHD symptoms in patients given dasotraline compared with those given placebo. 

Insomnia were more than four times more frequent among patients given dasotraline than among those given placebo. There was no evidence of the frequency of insomnia being dose-dependent. 

Similarly, patients given dasotraline were more than four times more likely to report decreased appetite than those receiving placebo. In this case, however, the effect was clearly dose-dependent, rising from 3x for 2mg to 4x for 4mg to 5x for 6mg and almost 8x for 8mg. 

The authors concluded, “dasotraline can reduce the core symptoms of ADHD, that is, hyperactivity/impulsivity and inattentiveness, leading to an overall improvement of ADHD compared to placebo. Dasotraline can also improve clinician-determined patients’ global functioning compared to the placebo. The most common adverse drug reactions related to dasotraline were insomnia and decreased appetite. However, to fill the knowledge gap, multicentric randomized active-controlled clinical trials are warranted in this domain for a successful translation into clinical practice.” 

Weighing these less than impressive initial results against the cost of further RCTs, Sunovion withdrew its application for approval by the Food and Drug Administration, stating, “while Sunovion considers dasotraline to be a promising, novel treatment for binge eating disorder and ADHD, we believe that further clinical studies would be needed to support a regulatory approval for dasotraline in these indications.” 

July 25, 2024

Meta-Analysis: Young People with ADHD Experience Serious Social Cognition Impairments

Meta-analysis Concludes Children and Adolescents with ADHD Experience Serious Impairments in Social Cognition, Affecting Social Functioning

Children and adolescents with ADHD are known to have difficulties in relating to family members, peers, and teachers. Over the long run this can contribute to anxiety or even delinquency. 

Several cognitive functions that allow individuals to process social information and interact with others contribute to shaping everyday social interactions. These include: 

  • Theory of mind (ToM): Being able to attribute mental states to others, and thus explain and predict their behaviors. 
  • Empathy: Being able to feel an appropriate emotion in response to another person’s mental state, and thereby understand others’ feelings. 
  • Emotion recognition: Being able to identify emotions in facial expressions and other communication cues, such as voice and body position. 

A European research team performed a systematic search of the peer-reviewed medical literature to conduct meta-analyses of ToM, Empathy, Facial and Non-Facial Emotion Recognition in children and adolescents with ADHD when compared to typical development. As a comparison measure, they also included Everyday Social Skills (using self, parent, teacher, or clinician questionnaires/interviews of social skills) as an outcome. 

The search yielded 142 case-control studies (including dissertations) with a total of 16,283 participants. 

Meta-analysis of 82 studies with a combined total of 10,770 participants found a very large effect size impairment in everyday social skills among children and adolescents with ADHD when compared with typically developing peers. Adjusting for covariates only strengthened the finding. There was no sign of publication bias. 

This was mirrored in three out of five measures of social cognition: 

  • Theory of mind (ToM): Meta-analysis of 49 studies with a total of 2,449 participants identified a large effect size impairment among children and adolescents with ADHD when compared with typically developing peers. Adjusting for covariates made no difference in the outcome. There was no sign of publication bias. 
  • Empathy: Meta-analysis of twelve studies combining 916 individuals yielded a medium effect size impairment among children and adolescents with ADHD. But there were strong signs of publication bias, and the outcome lost significance after adjusting for covariates (perhaps because it became under-powered with three studies pooling only 151 persons). 
  • Facial emotion recognition: Meta-analysis of 43 studies with a total of 3,369 participants reported a medium effect size impairment among children and adolescents with ADHD after adjusting for covariates. There was absolutely no indication of publication bias. 
  • Non-facial emotion recognition: Meta-analysis of eight studies encompassing 707 persons reported a small effect size impairment with signs of publication bias that became insignificant after adjusting for covariates. 

The team concluded, “Our findings show that children and adolescents with ADHD have deficits in ToM, Facial Emotion Recognition, and Everyday Social Skills, three domains that warrant clinical attention.” 

July 22, 2024