April 1, 2021
We know from many studies that ADHD is associated with a slightly lower intelligence quotient (IQ) and with problems in thinking known as executive function deficits. If that's the case, you might think that people with a high IQ cannot have ADHD. You would be wrong. Data on groups sometimes mislead us about individuals. Although on average, ADHD people have IQ scores that are about 9 points lower than others, there is a wide spread of IQs in both ADHD and non-ADHD people. So many people with ADHD have higher IQs than those without ADHD and vice-versa. Moreover, studies of people with high IQs support the idea that ADHD can be validly diagnosed among very intelligent individuals.
A series of studies using Antshel and colleagues showed that the clinical profile of high IQ ADHD was very similar to what has been observed for ADHD in general. For example, like their less intelligent counterparts, high IQ ADHD children have an increased risk for mood, anxiety, and disruptive behavior disorders. Children with a high IQ and ADHD showed a pattern of familial transmission as well as cognitive, psychiatric, and behavioral impairments consistent with the diagnosis of ADHD. The degree to which ADHD persisted into adulthood was also similar between the two groups.
In studies of adults with ADHD, the same group concluded that "adults with ADHD and a high IQ display patterns of functional impairments, familiarity and psychiatric co-morbidities that parallel those found in the average-IQ adult ADHD population." Of particular interest, despite their high intelligence, High-IQ adults with ADHD show impaired executive functioning, and their performance on tests of executive functioning predicted life impairments.
Why are these data important? Milioni and colleagues argue that among higher IQ adults with ADHD, a higher degree of intellectual efficiency may compensate for deficits in executive functions. This ability to compensate allows them to succeed in many tasks, which otherwise might have been impaired by their ADHD symptoms. But, in many cases, such compensation is not sufficient or is too burdensome. When compensation fails, ADHD symptoms and other impairments emerge. When this occurs later in life, some clinicians are reluctant to diagnose ADHD. Caution is warranted, but clinicians need to know that the diagnosis of ADHD among high IQ is valid.
Antshel, K. M., S. V. Faraone, et al. (2008). "Temporal stability of ADHD in the high-IQ population: results from the MGH Longitudinal Family Studies of ADHD." J Am Acad Child Adolesc Psychiatry47(7): 817-825.
Antshel, K. M., S. V. Faraone, et al. (2009). "Is adult attention deficit hyperactivity disorder a valid diagnosis in the presence of high IQ?" Psychol Med39(8):1325-1335.
Antshel, K. M., S. V. Faraone, et al. (2010)."Executive functioning in high-IQ adults with ADHD."Psychol Med40(11): 1909-1918.
Antshel, K. M., S. V. Faraone, et al. (2007). "Inattention deficit hyperactivity disorder a valid diagnosis in the presence of high IQ? Results from the MGH Longitudinal Family Studies of ADHD."child Psychol Psychiatry48(7): 687-694.
Katusic, M. Z., R. G. Voigt, et al. (2011)."Attention-deficit hyperactivity disorder in children with high intelligence quotient: results from a population-based study." JDevBehavPediatr32(2): 103-109.
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.”
In the general population, most mothers experience mood disturbances right after childbirth, commonly known as postpartum blues, baby blues, or maternity blues. Yet only about one in six develop symptoms with a duration and magnitude that require treatment for depressive disorder, and one in ten for anxiety disorder.
To what extent does ADHD contribute to the risk of such disorders following childbirth? A Swedish study team used the country’s single-payer health insurance database and other national registers to conduct the first nationwide population study to explore this question.
They used the medical birth register to identify all 420,513 women above 15 years of age who gave birth to their first child, and all 352,534 who gave birth to their second child, between 2005 and 2013. They excluded miscarriages. They then looked for diagnoses of depression and/or anxiety disorders up to a year following childbirth.
In the study population, 3,515 mothers had been diagnosed with ADHD, and the other 769,532 had no such diagnosis.
Following childbirth, depression disorders were five times more prevalent among mothers with ADHD than among their non-ADHD peers. Excluding individuals with a prior history of depression made little difference, lowering the prevalence ratio to just under 5. Among women under 25, the prevalence ratio was still above 3, while for those 25 and older it was above 6.
Similarly, anxiety disorders were over five times more prevalent among mothers with ADHD than among their non-ADHD peers. Once again, excluding individuals with a prior history of depression made little difference, lowering the prevalence ratio to just under 5. Among women under 25, the prevalence ratio was still above 3, while for those 25 and older it was above 6.
The team cautioned, “There is a potential risk of surveillance bias as women diagnosed with ADHD are more likely to have repeated visits to psychiatric care and might have an enhanced likelihood of also being diagnosed with depression and anxiety disorders postpartum, compared to women without ADHD.”
Nevertheless, they concluded, “ADHD is an important risk factor for both depression and anxiety disorders in the postpartum period and should be considered in the post- pregnancy maternal care, regardless of sociodemographic factors and the presence of other psychiatric disorders. Parental education prior to conception, psychological surveillance during, and social support after childbirth should be provided to women diagnosed with ADHD.”
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