February 4, 2021

New insights into the brains of people living with ADHD and those with ADHD symptoms.

The ENIGMA-ADHD Working Group published their second large study on the brains of people with ADHD in the American Journal of Psychiatry this month. In this second study, the focus was on the cerebral cortex, which is the outer layer of the brain.

ADHD symptoms include inattention and/or hyperactivity and acting impulsively. The disorder affects more than one in 20 (5.3%) children, and two-thirds of those diagnosed continue to experience symptoms as adults.

In this study, researchers found subtle differences in the brain’s outer layer - the cortex - when they combined brain imaging data on almost 4,000 participants from 37 research groups worldwide. The differences were only significant for children and did not hold for adolescents or adults. The childhood effects were most prominent and widespread for the surface area of the cortex. More focal changes were found in the thickness of the cortex. All differences were subtle and detected only at a group level, and thus these brain images cannot be used to diagnose ADHD or guide its treatment.

These subtle differences in the brain’s cortex were not limited to people with the clinical diagnosis of ADHD: they were also present - in a less marked form - in youth with some ADHD symptoms. This second finding results from a collaboration between the ENIGMA-ADHD Working Group and the Generation-R study from Rotterdam, which has brain images on 2700 children aged 9-11 years from the general population. The researchers found more symptoms of inattention to be associated with a decrease in cortical surface area. Furthermore, siblings of those with ADHD showed changes to their cortical surface area that resembled their affected sibling. This suggests that familial factors such as genetics or shared environment may play a role in brain cortical characteristics.

This is the largest study to date to look at the cortex of people with ADHD. It included 2246 people with a diagnosis of ADHD and 1713 people without, aged between four and 63 years old. This is the second study published by the ENIGMA-ADHD Working Group; the first examined structures that are deep in the brain. The ADHD Working Group is one of over 50 working groups of the ENIGMA Consortium, in which international researchers pull together to understand the brain alterations associated with different disorders and the role of genetic and environmental factors in those alterations.

The authors say the findings could help improve understanding of the disorder. ‘We identify cortical differences that are consistently associated with ADHD by combining data from many different research groups internationally. We find that the differences extend beyond narrowly-defined clinical diagnoses and are seen, in a less marked manner, in those with some ADHD symptoms and in unaffected siblings of people with ADHD. This finding supports the idea that the symptoms underlying ADHD may be a continuous trait in the population, which has already been reported by other behavioral and genetic studies.’. In the future, the ADHD Working Group hopes to look at additional key features in the brain- such as the structural connections between brain areas – and to increase the representation of adults affected by ADHD, in whom limited research has been performed to date. 

See: https://ajp.psychiatryonline.org/doi/10.1176/appi.ajp.2019.18091033

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Northern Finnish Population Study Finds ADHD Slashes Higher Education Attainment, Comorbidity of ADHD + ODD much worse

Background:

Although ADHD typically begins in childhood, its symptoms frequently continue into adulthood, and it is widely acknowledged as having a lifelong prevalence for most persons with ADHD. 

ADHD symptoms are linked to poor academic performance, mainly due to cognitive issues like compromised working memory. These symptoms lead to long-term negative academic outcomes and difficulty in achieving higher educational degrees. 

Oppositional Defiant Disorder (ODD) often co-occurs with ADHD. In community samples, it appears in about 50–60% of those with ADHD. ODD symptoms include an angry or irritable mood, vindictiveness toward others, and argumentative or defiant behavior that lasts more than 6 months and significantly disrupts daily life.  

Since ODD tends to co-occur with ADHD, research on pure ODD groups without ADHD is limited, especially in community samples. This longitudinal study aimed to examine the impact of ADHD and ODD symptoms in adolescence on academic performance at age 16 and educational attainment by age 32. 

Study:

Finland, like other Nordic countries, has a single-payer health insurance system that includes virtually all residents. A Finnish research team used the Northern Finnish Birth Cohort to include all 9,432 children born from July 1, 1985, through June 30, 1986, and followed since then. 

ADHD symptoms were measured at age 16 using the Strengths and Weaknesses of ADHD symptoms and Normal-behaviors (SWAN) scale. 

Symptoms of ODD were screened using a 7-point rating scale similar to the SWAN scale, based on eight DSM-IV-TR criteria: “Control temper”, “Avoid arguing with adults”, “Follow adult requests or rules”, “Avoid deliberately annoying others”, “Assume responsibility for mistakes or misbehaviour”, “Ignore annoyances from others”, “Control anger and resentment”, and “Control spitefulness and vindictiveness.” 

Higher education attainments were determined at age 32. 

Results:

After adjusting for the educational attainments of the parents of the subjects, family type, and psychiatric disorders other than ADHD or ODD, males with ADHD symptoms at age 16 had a quarter, and females a little over a third, of the higher education attainments of peers without ADHD symptoms at age 32.  

With the same adjustments, males with ODD symptoms alone had two-thirds, and females 80%, of the higher education attainments of peers without ODD, but neither outcome was statistically significant. 

However, all participants with combined ADHD and ODD symptoms at age 16 had roughly one-fifth of the higher education attainments of peers without such symptoms upon reaching age 32. 

Interpretation: 

The team concluded, “The findings that emerged from this large longitudinal birth cohort study showed that the co-occurrence of ODD and ADHD symptoms in adolescence predicted the greatest deficits of all in educational attainment in adulthood.” 

This study highlights the significant, long-lasting impact that co-occurring ADHD and ODD symptoms can have on educational outcomes well into adulthood. It underscores the importance of addressing both disorders together during adolescence to help improve future academic success.

July 1, 2025

U.S. Nationwide Study Finds Down Syndrome Associated with 70% Greater Odds of ADHD

The Background:

Down syndrome (DS) is a genetic disorder resulting from an extra copy of chromosome 21. It is associated with intellectual disability. 

Three to five thousand children are born with Down syndrome each year. They have higher risks for conditions like hypothyroidism, sleep apnea, epilepsy, sensory issues, infections, and autoimmune diseases. Research on ADHD in patients with Down syndrome has been inconclusive. 

The Study:

The National Health Interview Survey (NHIS) is a household survey conducted by the National Center for Health Statistics at the CDC. 

Due to the low prevalence of Down syndrome, a Chinese research team used NHIS records from 1997 to 2018 to analyze data from 214,300 children aged 3 to 17, to obtain a sufficiently large and nationally representative sample to investigate any potential association with ADHD. 

DS and ADHD were identified by asking, “Has a doctor or health professional ever diagnosed your child with Down syndrome, Attention Deficit Hyperactivity Disorder (ADHD), or Attention Deficit Disorder (ADD)?” 

After adjusting for age, sex, and race/ethnicity, plus family highest education level, family income-to-poverty ratio, and geographic region, children and adolescents with Down syndrome had 70% greater odds of also having ADHD than children and adolescents without Down syndrome. There were no significant differences between males and females. 

The Take-Away:

The team concluded, “in a nationwide population-based study of U.S. children, we found that a Down syndrome diagnosis was associated with a higher prevalence of ASD and ADHD. Our findings highlight the necessity of conducting early and routine screenings for ASD and ADHD in children with Down syndrome within clinical settings to improve the effectiveness of interventions.” 

June 27, 2025

Meta-analysis Explores Link Between ADHD and Homelessness Among Children and Adolescents

An estimated 150 million children and adolescents live on the streets worldwide. In the U.S., roughly 1.5 million experience homelessness annually. Homelessness increases the risk of health issues, violence, early pregnancy, substance use, vaccine-preventable diseases, mental disorders, suicidal behavior, and early death. 

Rates of anxiety, major depression, conduct disorders, and post-traumatic stress disorder are higher among school-age homeless children compared to their housed peers.  

However, there has been limited attention to ADHD, leading a French research team to conduct a systematic review and meta-analysis of its prevalence among homeless children and adolescents.  

The inclusion criteria required that participants be homeless, under 19 years of age at baseline, and have ADHD identified through a screening tool, self-report, or clinical assessment. 

Results:

Meta-analysis of 13 studies with a combined total of 2,878 individuals found indications of ADHD in almost one in four homeless children and adolescents. There was no sign of publication bias, but considerable variation in estimates across studies. 

The team found a dose-response effect. Meta-analysis of six studies with 1,334 participants under 12 years old reported 13% with indications of ADHD. Meta-analysis of five studies encompassing 991 individuals, 12 through 18 years old, found an ADHD rate of 43%. The ADHD rate among adolescents was 3.3 times greater than among children

There were no significant differences among countries. 

Moreover, limiting the meta-analysis to the seven studies with 1,538 participants that relied on clinical ADHD diagnoses, the gold standard,  resulted in an ADHD prevalence of 23%

The team concluded, “The review of 13 studies revealed that ADHD is common in homeless children and adolescents, suggesting that homelessness may contribute to the development or exacerbation of ADHD symptoms. Conversely, ADHD with other comorbidities may increase the likelihood of homelessness. Reintegrating these children and adolescents into care systems and ensuring access to public health interventions tailored for homeless families and youth is imperative for breaking the cycle of homelessness and improving long-term trajectories.” 

In other words, this review not only confirmed a strong link between homelessness and ADHD in children and youth, but also suggested a complex, cyclical relationship. Providing tailored health care and support for these vulnerable groups is crucial to interrupt this cycle and help improve their future outcomes.

June 23, 2025