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Taiwanese Population Study Finds Strong Association Between Cleft Lip and Palate and Subsequent ADHD
Congenital cleft lip and palate (CCLP) are birth defects associated with genetic and environmental factors. The latter include heavy maternal consumption of alcohol and fetal exposure to retinoid drugs derived from vitamin A.
Methods:
Taiwan has an island-wide single-payer health insurance system that reaches over 99% of the population. To explore the relationship between CCLP and various psychiatric disorders including ADHD, a Taiwanese study team used the island’s National Health Insurance Research Database to identify all 1,158 children and adolescents with CCLP during a ten-year period. They matched them ten-to-one with 11,580 age and sex-paired controls without CCLP.
Summary of Results:
Further adjusting for demographic data (income, residence) and family history of major psychiatric disorders, children and adolescents with CCLP were more than seven times more likely to be diagnosed with ADHD during the follow-up period than controls. Patients with both cleft palate and cleft lip were more than nine times more likely to be subsequently diagnosed with ADHD than controls.
Patients with CCLP were also six times more likely to be diagnosed with autism spectrum disorder and more than seven times as likely to be diagnosed with schizophrenia as non-CCLP controls. They were also more likely to be diagnosed with bipolar disorder or major depressive disorder, but these results did not reach statistical significance.
Conclusion:
This study highlights a significant association between congenital cleft lip and palate (CCLP) and an increased risk of developing ADHD, with CCLP patients being more than seven times as likely to be diagnosed with the disorder. Additionally, CCLP was linked to a higher prevalence of other psychiatric conditions, including autism spectrum disorder and schizophrenia. These findings underscore the importance of monitoring mental health in individuals with CCLP and call for further research into the risk factors connecting these birth defects with psychiatric disorders.
Understanding Attention to Social Images in Children with ADHD and Autism
NEWS TUESDAY: Understanding Attention to Social Images in Children with ADHD and Autism
In the field of mental health, professionals often use a variety of tools to diagnose and understand neurodevelopmental disorders such as Autism Spectrum Disorder (ASD) and Attention-Deficit/Hyperactivity Disorder (ADHD). One such tool is the Autism Diagnostic Observation Schedule (ADOS), which is specifically designed to help diagnose autism. However, the ADOS wasn't originally intended for children who have both autism and ADHD, though this comorbidity is not uncommon.
A recent study aimed to explore how children with ADHD, autism, or both, pay attention to social images, such as faces. The study focused on using eye-tracking technology to measure where children direct their gaze when viewing pictures, and how long they look at certain parts of the image. This is important because differences in visual attention can provide insights into the nature of these disorders.
The researchers included 84 children in their study, categorized into four groups: those with ASD, those with ADHD, those with both ASD and ADHD, and neurotypical (NT) children without these conditions. During the study, children were shown social scenes from the ADOS, and their eye movements were recorded. The ADOS assessment was administered afterward. To ensure that the results were not influenced by medications, children who were on stimulant medications for ADHD were asked to pause their medication temporarily.
The results of the study showed that children with ASD, whether they also had ADHD or not, tended to spend less time looking at faces compared to children with just ADHD or NT children. The severity of autism symptoms, measured by the Social Communication Questionnaire (SCQ), was associated with reduced attention to faces. Interestingly, ADHD symptom severity, measured by Conners' Rating Scales (CRS-3), did not correlate with how children looked at faces.
These findings suggest that measuring visual attention might be a valuable addition to the assessment process for ASD, especially in cases where ADHD is also present. The study indicates that if a child with ADHD shows reduced attention to faces, it might point to additional challenges related to autism. The researchers noted that more studies with larger groups of children are needed to confirm these findings, but the results are promising. They hope that such measures could eventually enhance diagnostic processes and help in managing the complexities of cases involving comorbidity of ADHD and ASD.
This research opens up the possibility of using eye-tracking as a supplementary diagnostic tool in the assessment of autism, providing a more nuanced understanding of how attentional differences in social settings are linked to ASD and ADHD.
NEW STUDY: RASopathies Influences on Neuroanatomical Variation in Children
NEW STUDY: RASopathies Influences on Neuroanatomical Variation in Children
This study investigates how certain genetic disorders, called RASopathies, affect the structure of the brain in children. RASopathies are conditions caused by mutations in a specific signaling pathway in the body. Two common RASopathies are Noonan syndrome (NS) and neurofibromatosis type 1 (NF1), both of which are linked to a higher risk of autism spectrum disorder (ASD) and attention deficit and hyperactivity disorder (ADHD).
The researchers analyzed brain scans of children with RASopathies (91 participants) and compared them to typically developing children (74 participants). They focused on three aspects of brain structure: surface area (SA), cortical thickness (CT), and subcortical volumes.
The results showed that children with RASopathies had both similarities and differences in their brain structure compared to typically developing children. They had increased SA in certain areas of the brain, like the precentral gyrus, but decreased SA in other regions, such as the occipital regions. Additionally, they had thinner CT in the precentral gyrus. However, the effects on subcortical volumes varied between the two RASopathies: children with NS had decreased volumes in certain structures like the striatum and thalamus, while children with NF1 had increased volumes in areas like the hippocampus, amygdala, and thalamus.
Overall, this study highlights how RASopathies can impact the development of the brain in children. The shared effects on SA and CT suggest a common influence of RASopathies on brain development, which could be important for developing targeted treatments in the future.
In summary, understanding how these genetic disorders affect the brain's structure can help researchers and healthcare professionals develop better treatments for affected children.
News Tuesday: Integrating Cognition and Eye Movement
Integrating Cognitive Factors and Eye Movement Data in Reading Predictive Models for Children with Dyslexia and ADHD-I
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.
Exploring Gut Microbiota and Diet in Autism and ADHD: What Does the Research Say?
In recent years, there has been growing interest in understanding the connection between our gut microbiota (the community of microorganisms in our digestive system) and various neurodevelopmental disorders like autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD). A new study by Shunya Kurokawa and colleagues dives deeper into this area, comparing dietary diversity and gut microbial diversity among children with ASD, ADHD, their normally-developing siblings, and unrelated volunteer controls. Let's unpack what they found and what it means.
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:
Gut Microbial Diversity: The researchers found significant differences in alpha-diversity indices (like Chao 1 and Shannon index) among the groups. Notably, children with ASD had lower gut microbial diversity compared to unrelated neurotypical controls. This suggests disorder-specific differences in gut microbiota, particularly in children with ASD.
Dietary Diversity: Surprisingly, dietary diversity (assessed using the Shannon index) did not differ significantly among the groups. This finding implies that while gut microbial diversity showed disorder-specific patterns, diet diversity itself might not be the primary factor driving these differences.
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.
Swedish Population Study Confirms Association Between ADHD and Height
Nationwide population study in Sweden confirms association between ADHD and shorter height in children and adolescents, suggests stimulant medications are not a factor
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.
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.”
Swedish nationwide population study finds mothers with ADHD have elevated risk of depression and anxiety disorders after childbirth
Swedish nationwide population study finds mothers with ADHD have elevated risk of depression and anxiety disorders after childbirth
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.
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.”
Meta-analysis suggests acupuncture might offer effective treatment for ADHD, but suffers from methodological flaws
Meta-analysis suggests acupuncture might offer effective treatment for ADHD, but suffers from methodological flaws
Acupuncture is a form of traditional Chinese medicine that pricks the skin with needles, either to alleviate pain or to treat a variety of physical, mental, and emotional conditions.
Noting that previous “systematic reviews concluded that currently available data on the clinical effectiveness of acupuncture for treating ADHD are yet to be sufficient to support its routine use,” a South Korean study team conducted an updated systematic search of the medical literature for randomized controlled trials (RCTs) comparing acupuncture with drug treatment for children and adolescents with ADHD. There were no restrictions on language or publication type.
Only two of the meta-analyses involved more than two RCTs.
One of them, of six RCTs with a combined 541 participants, reported total treatment efficacy of acupuncture to be at least equal to that of conventional treatment with ADHD medicines.
Another, of five RCTs with a total of 351 participants, reported total treatment efficacy of combined acupuncture and ADHD drugs to be at least equal to that of conventional treatment with ADHD medicines.
Two RCTs with a Noting that previous “systematic reviews concluded that currently available data on the clinical effectiveness of acupuncture for treating ADHD are yet to be sufficient to support its routine use,” a South Korean study team conducted an updated systematic search of the medical literature for randomized controlled trials (RCTs) comparing acupuncture with drug treatment for children and adolescents with ADHD. There were no restrictions on language or publication type.
Only two of the meta-analyses involved more than two RCTs.
One of them, of six RCTs with a combined 541 participants, reported total treatment efficacy of acupuncture to be at least equal to that of conventional treatment with ADHD medicines.
Another, of five RCTs with a total of 351 participants, reported total treatment efficacy of combined acupuncture and ADHD drugs to be at least equal to that of conventional treatment with ADHD medicines.
Two RCTs with a combined 152 participants reported a large effect size improvement in hyperactivity/impulsivity symptoms from acupuncture treatment versus conventional drug treatment.
From this one could superficially conclude that acupuncture is at least as effective for treating ADHD as the medicines currently considered to be the standard of care, and that there is no need to combine acupuncture with drug treatment.
However, there were numerous methodological shortcomings:
- No effort was made to look for publication bias.
- There were few RCTs, and the combined number of participants was relatively small.
- Only one of the six RCTs in the first meta-analysis and none of the five RCTs in the second meta-analysis was rated “low risk of bias.”
- Though nowhere stated in the journal article, there may have been cultural bias as well. All studies included in the meta-analyses were conducted in China. As China has emerged as a global superpower, it has been eager to portray its traditional medicine as at least equal if not superior to forms of medicine originating elsewhere.
- The authors noted, “the quality of the studies included in this systematic review was poor. Assessing the blinding of studies is a major aspect in determining the risk of bias of a study, but most of the studies did not provide any relevant information.”
The authors concluded, “The current evidence on AT [acupuncture treatment] is still too limited to support its routine use in treating ADHD.”
152 participants reported a large effect size improvement in hyperactivity/impulsivity symptoms from acupuncture treatment versus conventional drug treatment.
From this one could superficially conclude that acupuncture is at least as effective for treating ADHD as the medicines currently considered to be the standard of care, and furthermore that there is no need to combine acupuncture with drug treatment.
However, there were numerous methodological shortcomings:
- No effort was made to look for publication bias.
- There were few RCTs, and the combined number of participants was relatively small.
- Only one of the six RCTs in the first meta-analysis and none of the five RCTs in the second meta-analysis was rated “low risk of bias.”
- Though nowhere stated in the journal article, there may have been cultural bias as well. All studies included in the meta-analyses were conducted in China. As China has emerged as a global superpower, it has been eager to portray its traditional medicine as at least equal if not superior to forms of medicine originating elsewhere.
- The authors noted, “the quality of the studies included in this systematic review was poor. Assessing the blinding of studies is a major aspect in determining the risk of bias of a study, but most of the studies did not provide any relevant information.”
The authors concluded, “The current evidence on AT [acupuncture treatment] is still too limited to support its routine use in treating ADHD.”
New Zealand national birth cohort finds young adults with ADHD overrepresented at all stages of the criminal justice system
National Birth Cohort Finds Young Adults with ADHD Over-represented in Criminal Justice System
Using Statistics New Zealand’s Integrated Data Infrastructure (IDI), a large database of linked de-identified administrative and survey data about people and households, a local study team examined a three-year birth cohort (mid-1992 through mid-1995) totaling 149,076 persons.
Using Statistics New Zealand’s Integrated Data Infrastructure (IDI), a large database of linked de-identified administrative and survey data about people and households, a local study team examined a three-year birth cohort (mid-1992 through mid-1995) totaling 149,076 persons.
The team assessed the presence of ADHD within this cohort through diagnosis codes and inference from medication dispensing, where there was at least one code relating to an ADHD diagnosis in the medication datasets. This subgroup consisted of 3,975 persons.
Next, they related this information to criminal justice system interactions of increasing severity, starting with police proceedings, and continuing with court charges, court convictions, and incarcerations. These interactions were tracked during an eight-year period from participants’ 17th birthday through their 25th birthday.
In this same period the team also tracked types of offenses: against people; against property; against organizations, government, and community; and violent offenses.
In all cases, the study team adjusted for gender, ethnicity, deprivation, and area of residence as potential confounders.
With these adjustments, young adults with ADHD were over twice as likely as their typically developing peers to be proceeded against by police, to be charged with an offense, and to be convicted. They were almost five times as likely to be incarcerated.
With the same adjustments, young adults with ADHD were over twice as likely as their typically developing peers to be convicted of offenses against organizations, government, and community. They were almost three times as likely to be convicted of crimes against persons, and over three and a half times more likely to be convicted of either violent offenses or offenses against property.
The authors noted, “The greater effect size for incarceration observed in our study may be due to the lack of control for comorbid conditions such as CD [conduct disorder], which are known criminogenic risk factors.”
They also noted, “The sharp increase in the risk of incarceration observed may also signal differences in the NZ justice system’s approach to ADHD, which may be less responsive to the condition than other nations, particularly the steps in the justice system between conviction and sentence. This would suggest that the UNCRPD [United Nations Convention on the Rights of Persons with Disabilities] obligations of equal recognition before the law and the elimination of discrimination on the basis of disability are not being met for individuals with ADHD in NZ.”
They concluded, “Our findings revealed that not only were individuals with ADHD overrepresented at all stages of the CJS [criminal justice system] and offense types examined, there was also a pattern of increasing risk for CJS interactions as these individuals moved through the system. These results highlight the importance of early identification and responsivity to ADHD within the CJS and suggest that the NZ justice system may require changes to both of these areas to ensure that young individuals with ADHD receive equitable access to, and treatment within, the CJS.”
Nationwide population studies: atomoxetine not associated with birth defects
Nationwide population studies: atomoxetine not associated with birth defects
Treatment for ADHD among women of reproductive age is increasingly common. That means we need to know whether ADHD medications have any tendency to increase the risk of birth defects.
Treatment for ADHD among women of reproductive age is increasingly common.
That means we need to know whether ADHD medications have any tendency to increase the risk of birth defects. Previous studies have looked mostly at ADHD medications that are central nervous system stimulants, especially methylphenidate and amphetamines.
Atomoxetine is the most widely prescribed non-stimulant for treating ADHD. It acts indirectly, by selectively inhibiting the removal of norepinephrine, a neurotransmitter that mobilizes the brain and body for action.
To explore whether atomoxetine might be associated with any higher risk of birth defects, an international study team examined nationwide population data from four Nordic countries with universal single-payer health insurance systems – Denmark, Norway, Sweden, and Iceland – along with nationwide data from the U.S. Medicaid system, which is likewise single-payer, and covers roughly half of all births in the U.S.
They compared the prevalence of major birth defects among infants born to women exposed to atomoxetine in the first trimester (three months) of pregnancy to the prevalence among infants born to women not exposed to any ADHD drug during the period beginning three months before their last menstrual period and concluding at the end of the first trimester.
The team adjusted for maternal characteristics such as maternal age, calendar year of delivery, childbirth and medical characteristics, psychiatric conditions, high blood pressure, diabetes, kidney disease, obesity, and smoking.
In more than 2.4 million births in the four Nordic countries, and almost 1.8 million births in the U.S., there was absolutely no sign of increased prevalence of major infant malformations among infants born to mothers taking atomoxetine.
More specifically looking at heart defects, there was again no significant association with maternal atomoxetine use, either in the Nordic population, the U.S. population, or the combined populations.
For limb malformations, there was again no significant association between maternal atomoxetine use and birth defects in the combined populations. There was an appearance of a significant association in the Nordic population, but that was based on only 5 instances, and because there were zero instances in the U.S. population, there was no net association at all in the combined population of more than 4.2 million.
The team concluded, “We found no increased prevalence of major congenital malformations overall associated with atomoxetine use in early pregnancy. The increased prevalence of limb malformations in the Nordic countries was not observed in the US. … Given the low absolute risk of both of these outcomes, these results are reassuring from a public health perspective and provide important information in the consideration of whether to continue treatment with atomoxetine during pregnancy.”
Danish population study: Sex chromosome abnormalities increase risk of ADHD
Danish population study: Sex chromosome abnormalities increase risk of ADHD
Sex chromosome abnormalities are replication errors that produce an atypical number of sex chromosomes relative to the typical 46,XY and 46,XX arrangements.
Sex chromosome abnormalities are replication errors that produce an atypical number of sex chromosomes. Most people have 23 pairs of chromosomes for a total of 46. One pair is called the sex chromosome pair. It is either XX (for biological females) or XY (for biological males). The term 46,XY refers to a typical biological male and the term 46,XX refers to the typical biological female.
In rare cases a person may have only 45 chromosomes due to having only one sex chromosome, the X chromosome (45,X). Some people, rarely, have an extra sex chromosome and are designated: 47,XXX, 47,XXY, and 47,XYY. These rare sex chromosome differences occur in between 0.5 and 1.3 per 1,000 livebirths.
These differences have physical manifestations. For example, 45,X is associated with shorter height and abnormal development of the ovaries. The other three are associated with greater height. 47,XXX is associated with premature ovarian failure and 47,XXY with low testosterone.
A Danish and U.S. team used data from Denmark’s single-payer universal health insurance system to assess the association of these sex chromosome differences with the prevalence of ADHD.
They performed a case-cohort study. The source population was all 1,657,449 singleton births in Denmark between May 1, 1981, and Dec 31, 2008. The cases consisted of all 93,608 individuals in this population who were diagnosed with any of five psychiatric disorders, including ADHD. These were compared with a cohort consisting of 50,615 individuals randomly selected from the source population.
The combined population prevalence of these four sex chromosome differences was 1.45 per 1,000. 47,XXY was the most common, at 1.23 per 1,000, followed by 47,XYY at .82 per 1,000, then 47,XXX at .66 per 1,000. 45,X was by far the least common, at less than .23 per 1,000.
All four conditions were associated with significantly increased risk of ADHD:
- 47,XXY roughly doubled the risk.
- 47,XXX increased the risk 2.5-fold.
- 47,XYY more than quadrupled the risk.
- 45,X more than sextupled the risk.
These data are intriguing because we know there are sex differences in the prevalence of ADHD but the causes of those differences are unknown.
Given that ADHD is more common in boys than girls, one would have predicted that having an extra Y chromosome would increase risk for ADHD. That is the case here but we also see that having an extra X chromosome also increases risk, which means that the impact of sex chromosomes on ADHD is not straightforward.
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