July 2, 2025

Swedish Nationwide Population Study Identifies Top Predictors of ADHD Diagnoses Among Preschoolers

Most preschool-aged children diagnosed with ADHD also exhibit comorbid mental or developmental conditions. Long-term studies following these children into adulthood have demonstrated that higher severity of ADHD symptoms in early childhood is associated with a more persistent course of ADHD. 

The Study: 

Sweden has a single-payer national health insurance system that covers virtually all residents, facilitating nationwide population studies. An international study team (US, Brazil, Sweden) searched national registers for predictors of ADHD diagnoses among all 631,695 surviving and non-emigrating preschoolers born from 2001 through 2007.  

Preschool ADHD was defined by diagnosis or prescription of ADHD medications issued to toddlers aged three through five years old.  

Predictors were conditions diagnosed prior to the ADHD diagnosis. 

A total of 1,686 (2.7%) preschoolers were diagnosed with ADHD, with the mean age at diagnosis being 4.6 years. 

The Numbers:

Adjusting for sex and birth year, the team reported the following predictors, in order of magnitude: 

  • Previous diagnosis of autism spectrum disorder increased subsequent likelihood of ADHD diagnosis twentyfold. 
  • Previous diagnosis of intellectual disability increased subsequent likelihood of ADHD diagnosis fifteenfold. 
  • Previous diagnosis of speech/language developmental disorders and learning disorders, as well as motor and tic disorders, increased subsequent likelihood of ADHD diagnosis thirteen-fold. 
  • Previous diagnosis of sleep disorders increased subsequent likelihood of ADHD diagnosis fivefold. 
  • Previous diagnosis of feeding and eating disorders increased subsequent likelihood of ADHD diagnosis almost fourfold. 
  • Previous diagnosis of gastroesophageal reflux disease (GERD) increased subsequent likelihood of ADHD diagnosis 3.5-fold. 
  • Previous diagnosis of asthma increased subsequent likelihood of ADHD diagnosis 2.4-fold. 
  • Previous diagnosis of allergic rhinitis increased subsequent likelihood of ADHD diagnosis by 70%. 
  • Previous diagnosis of atopic dermatitis or unintentional injuries increased subsequent likelihood of ADHD diagnosis by 50%. 

The Conclusion: 

This large population study underscores that many conditions present in early childhood can help predict an ADHD diagnosis in preschoolers. Recognizing these risk factors early may aid in identifying and addressing ADHD sooner, hopefully improving outcomes for children as they grow

Wagner Gurgel, Miguel Garcia-Argibay, Brian M. D’Onofrio, Henrik Larsson, and Guilherme V. Polanczyk, “Predictors of preschool attention-deficit/hyperactivity disorder diagnosis: a population-based study using national registers,” Journal of Child Psychology and Psychiatry (2025), 66:6, 834-845, https://doi.org/10.1111/jcpp.14093.

Related posts

ADHD Medication and Academic Achievement: What Do We Really Know?

Parents and teachers often ask: Does ADHD medication actually improve grades and school performance? The answer is: yes, but with important limitations. Medications are very effective at reducing inattention, hyperactivity, and impulsivity but their impact on long-term academic outcomes like grades and test scores is not as consistent.

In the Classroom

The medications for ADHD consistently: Improve attention, reduce classroom disruptions, increase time spent on-task and help children complete more schoolwork and homework. Medication can help children with ADHD access learning by improving the conditions for paying attention and persisting with work.

Does Medication Improve Test Scores and Grades?

This is where the picture gets more complicated.  Medications have  stronger effect on how much work is completed but a weaker effect on accuracy. Many studies show that children on medication attempt more problems in reading, math, and spelling, but the number of correct answers doesn’t always improve as much. Some studies find small but significant improvements in national exam scores and higher education entrance tests during periods when children with ADHD are medicated.

Grades improve, as well, but modestly. Large registry studies in Sweden show that students who consistently take medication earn higher grades than those who don’t. However, these gains usually do not close the achievement gap with peers who do not have ADHD.

Keep in mind that small improvements for a group as a whole mean that some children are benefiting greatly from medication and others not at all.  We have no way of predicting which children will improve and which do not. 

Medication Alone Isn’t Enough

Academic success depends on more than just reducing inattention, hyperactivity and impulsivity. Skills like organization, planning, studying, and managing long-term projects are also critical.  Medication cannot teach these skills.

So, in addition to medication, the patient's treatment program should include educational support (tutoring, structured study skills programs), behavioral interventions (parent training, classroom management strategies), and accommodations at school (extra time, reduced distractions, organizational aids) Parents should discuss with their prescriber which of these methods would be appropriate.

Conclusions 

ADHD medication is a powerful tool for reducing symptoms and supporting learning. It improves test scores and grades for some children, especially when taken consistently. But it is not a magic bullet for academic success. The best results come when medication is combined with educational and behavioral supports that help children build the skills they need to thrive in school and beyond.

September 17, 2025

Dose-dependent Association Found Between Childhood General Anesthesia and ADHD

Childhood General Anesthesia and Subsequent Diagnoses of ADHD

In December 2016, the U.S. Food and Drug Administration (FDA) warned “that repeated or lengthy use of general anesthetic and sedation drugs during surgeries or procedures in children younger than 3 years or in pregnant women during their third trimester may affect the development of children’s brains.” The FDA adds, “Health care professionals should balance the benefits of appropriate anesthesia against the potential risks, especially for procedures lasting longer than 3 hours or if multiple procedures are required in children under 3 years,” and “Studies in pregnant and young animals have shown that using these drugs for more than 3 hours caused widespread loss of brain nerve cells.”

That raises a concern that such exposure could lead to increased risk of psychiatric disorders, including ADHD.

Noting “There are inconsistent reports regarding the association between general anesthesia and adverse neurodevelopmental and behavioral disorders in children,” a South Korean study team conducted a nationwide population study to explore possible associations through the country’s single-payer health insurance database that covers roughly 97% of all residents.

The team looked at the cohort of all children born in Korea between 2008 and 2009, and followed them until December 31, 2017. They identified 93,717 children in this cohort who during surgery received general anesthesia with endotracheal intubation (a tube inserted down the trachea), and matched them with an equal number of children who were not exposed to general anesthesia.

The team matched the unexposed group with the exposed group by age, sex, birth weight, residential area at birth, and economic status.

They then assessed both groups for subsequent diagnoses of ADHD.

In general, children exposed to general anesthesia were found to have a 40% greater risk of subsequently being diagnosed with ADHD than their unexposed peers.

This effect was found to be dose dependent by several measures:

  • Duration of surgery: two-to-three-hour surgeries were associated with a 50% greater risk of subsequent ADHD, and surgeries of more than three hours with a 60% greater risk.
  • Number of exposures: two exposures were associated with a 54% increased risk, and three or more exposures with a 67% greater risk.
  • Placement in an Intensive Care Unit was associated with a 60% greater risk of ADHD.

All three measures were highly significant.

The authors concluded, “exposure to general anesthesia with ETI [endotracheal intubation] in children is associated with an increased risk of ADHD … We must recognize the possible neurodevelopmental risk resulting from general anesthesia exposure, inform patients and parents regarding this risk, and emphasize the importance of close monitoring of mental health. However, the risk from anesthesia exposure is not superior to the importance of medical procedures. Specific research is needed for the development of safer anesthetic drugs and doses.”

June 20, 2024

How Effective is Cognitive Training for Preschool Children?

How effective is cognitive training for preschool children?

A German team of researchers performed a comprehensive search of the medical literature and identified 35randomized controlled trials (RCTs) published in English that explored this question. Participating children were between three and six years old. Children with intellectual disabilities, sensory disabilities, or specific neurological disorders such as epilepsy were excluded.

The total number of participating preschoolers was over three thousand, drawn almost exclusively from the general population, meaning these studies were not specifically evaluating effects on children with ADHD. But given that ADHD results in poorer executive functioning, evidence of the effectiveness of cognitive training would suggest it could help partially reverse such deficits.

RCTs assign participants randomly to a treatment group and a group not receiving treatment but often receiving a placebo. But RCTs themselves vary in risk of bias, depending on:

  • whether the control condition was passive (i.e. waiting list or no treatment) or active/sham (an activity of similar duration and intensity to the treatment condition)
  • whether the outcome was measured by subjective rating (e.g. by questionnaires, susceptible to reporting biases) or more objective neuropsychological testing;
  • whether the assessment of outcome was by blinded assessors unaware of participants' treatment conditions;
  • whether there was a risk of bias from participants dropping out of the trial.

After evaluating the RCTs by these criteria, the team performed a series of meta-analyses.

Combining the 23 RCTs with over 2,000 children that measured working memory, they found that cognitive training led to robust moderate improvements. Looking only at the eleven most rigorously controlled studies strengthened the effect, with moderate-to-large gains.

Twenty-six RCTs with over 2,200 children assessed inhibitory control. When pooled, they indicated a small-to-moderate improvement from cognitive training. Including only the seven most rigorously controlled studies again strengthened the effect, boosting it into the moderate effect zone.

Twelve RCTs with over 1,500 participants tested the effects of cognitive training on flexibility. When combined, they pointed to moderate gains. Looking at only the four well-controlled studies boosted the effect to strong gains. Yet here there was evidence of publication bias, so no firm conclusion can be drawn.

Only four studies with a combined total of 119 preschoolers tested the effects on ADHD ratings. The meta-analysis found a small but non-significant improvement, very likely due to insufficient sampling. As the authors noted, "some findings of the meta-analysis are limited by the insufficient number of eligible studies. Specifically, more studies are needed which use blinded assessments of subjective ratings of ADHD ... symptoms ..."

The authors concluded that their meta-analyses revealed significant, mostly medium-sized effects of the preschool interventions on core EFs [executive functions] in studies showing the low risk of bias."

January 2, 2022

Here’s What the Wall Street Journal Got Wrong about the Medication Treatment of ADHD Patients: A Lesson in Science Media Literacy

A recent Wall Street Journal article raised alarms by concluding that many children who start medication for ADHD will later end up on several psychiatric drugs. It’s an emotional topic that will make many parents, teachers, and even doctors worry: “Are we putting kids on a conveyor belt of medications?”

The article seeks to shine a light on the use of more than one psychiatric medication for children with ADHD.   My biggest worry about the article is that it presents itself as a scientific study because they analyzed a database.  It is not a scientific study.  It is a journalistic investigation that does not meet the standards of a scientific report..

The WJS brings attention to several issues that parents and prescribers should think about. It documents that some kids with ADHD are on more than one psychiatric medication, and some are receiving drugs like antipsychotics, which have serious side effects.  Is that appropriate? Access to good therapy, careful evaluation, and follow-up care can be lacking, especially for low-income families.  Can that be improved?  On that level, the article is doing something valuable: it’s shining a spotlight on potential problems.

It is, of course, fine for a journalist to raise questions, but it is not OK for them to pretend that they’ve done a scientific investigation that proves anything. Journalism pretending to be science is both bad science and bad journalism.

Journalism vs. Science: Why Peer Review Matters

Journalists can get big datasets, hire data journalists, and present numbers that look scientific.  But consider the differences between Journalism and Science. These types of articles are usually checked by editors and fact-checkers. Their main goals are:

 Is this fact basically correct?

 Are we being fair?

 Are we avoiding legal problems?

But editors are not qualified to evaluate scientific data analysis methods.  Scientific reports are evaluated by experts who are not part of the project.  They ask tough questions like: 

Exactly how did you define ADHD? 

How did you handle missing data? 

Did you address confounding? 

Did you confuse correlation with causation?

If the authors of the study cannot address these and other technical issues, the paper is rejected.

The WSJ article has the veneer of science but lacks its methodology.  

Correlation vs. Causation: A Classic Trap

The article’s storyline goes something like this:  A kid starts ADHD medication.  She has additional problems or side effects caused by the ADHD medications.   Because of that, the prescriber adds more drugs.  That leads to the patient being put on several drugs.  Although it is true that some ADHD youth are on multiple drugs, the WSJ is wrong to conclude that the medications for ADHD cause this to occur.  That simply confuses correlation with causation, which only the most naïve scientist would do.

In science, this problem is called confounding. It means other factors (like how severe or complex a child’s condition is) explain the results, not just the thing we’re focused on (medication for ADHD). 

The WSJ analyzed a database of prescriptions.  They did not survey the prescribers who made the prescriptions of the patients who received them.  So they cannot conclude that ADHD medication caused the later prescriptions, or that the later medications were unnecessary or inappropriate. 

Other explanations are very likely.   It has been well documented that youth with ADHD are at high risk for developing other disorders such as anxiety, depression,  and substance use.  The kids in the WSJ database might have developed these disorders and needed several medications.  A peer-reviewed article in a scientific journal would be expected to adjust for other diagnoses. If that is not possible, as it is in the case of the WSJ’s database, a journal would not allow the author to make strong conclusions about cause-and-effect.

Powerful Stories Don’t Always Mean Typical Stories

The article includes emotional accounts of children who seemed harmed by being put on multiple psychiatric drugs.  Strong, emotional stories can make rare events feel common.  They also frighten parents and patients, which might lead some to decline appropriate care. 

These stories matter. They remind us that each data point is a real person.  But these stories are the weakest form of data.  They can raise important questions and lead scientists to design definitive studies, but we cannot use them to draw conclusions about the experiences of other patients.  These stories serve as a warning about the importance of finding a qualified provider,  not as against the use of multiple medications.  That decision should be made by the parent or adult patient based on an informed discussion with the prescriber.

Many children and adults with ADHD benefit from multiple medications. The WSJ does not tell those stories, which creates an unbalanced and misleading presentation.  

Newspapers frequently publish stories that send the message:  “Beware!  Doctors are practicing medicine in a way that will harm you and your family.”   They then use case studies to prove their point.  The title of the article is, itself, emotional clickbait designed to get more readers and advertising revenue.  Don’t be confused by such journalistic trickery.

What Should We Conclude?

Here’s a balanced way to read the article.  It is true that some patients are prescribed more than one medication for mental health problems.  But the article does not tell us whether this prescribing practice is or is not warranted for most patients.  I agree that the use of antipsychotic medications needs careful justification and close monitoring.  I also agree that patients on multiple medications should be monitored closely to see if some of the medications can be eliminated.  Many prescribers do exactly that, but the WSJ did not tell their stories.  

It is not appropriate to conclude that ADHD medications typically cause combined pharmacotherapy or to suggest that combined pharmacotherapy is usually bad. The data presented by the WSJ does not adequately address these concerns.  It does not prove that medications for ADHD cause dangerous medication cascades.

We have to remember that even when a journalist analyzes data, that is not the same as a peer-reviewed scientific study. Journalism pretending to be science is both bad science and bad journalism.

Oppositional Defiant Disorder, Autism, and ADHD: New Research Examines the Connection

Oppositional Defiant Disorder (ODD)—a pattern of chronic irritability, anger, arguing, or defiance—is one of the most challenging behavioral conditions families and clinicians face. 

A new study involving 2,400 children ages 3–17 offers one of the clearest pictures yet. Using parent-reported data from the Pediatric Behavior Scale, researchers compared how often ODD appears in Autism spectrum disorder (ASD), ADHD-Combined presentation (ADHD-C), ADHD-Inattentive presentation (ADHD-I), and those with both ASD and ADHD.

Results

ADHD-Combined + ODD: The Highest-Risk Group

Children with ADHD-Combined presentation show both hyperactivity/impulsivity and inattention.  They had the highest ODD rates of any single diagnosis: 53% of kids with ADHD-Combined met criteria for ODD.

But when autism was added to ADHD-Combined, the prevalence jumped to 62%. This group also had the highest overall ODD scores, suggesting more severe or more impairing symptoms. 

This synergy matters: while autism alone increases ODD risk, the presence of ADHD-Combined is what pushes prevalence into the majority range. Other groups showed lower, but still significant, rates of ODD:

  • Autism + ADHD-Inattentive: 28%
  • Autism Only: 24%
  • ADHD-Inattentive Only: 14%

These findings echo what clinicians often see: children with inattentive ADHD, while struggling significantly with attention and learning, tend to show fewer behavioral conflict patterns than those with hyperactive/impulsive symptoms.

It is important to note that ODD is considered to have two main components. Across all diagnostic groups, ODD consistently broke down into these two components: either Irritable/Angry (emotion-based) or Oppositional/Defiant (behavior-based). But the balance between these components differed depending on diagnosis. Notably, Autism + ADHD-Combined showed higher levels of the irritable/angry component than ADHD-Combined alone. The oppositional/defiant component did not differ much between groups. This suggests that autism elevates the emotional side of ODD more than the behavioral side, which is important for clinicians to note before tailoring interventions.

Understanding ADHD , ASD, & Comorbidity:

The study notes that autism, ADHD, and ODD often cluster together, with 55–90% comorbidity in some combinations.

As the authors explain, The high co-occurrence of ADHD-Combined in autism (80% in our study) largely explains the high prevalence of ODD in autism.” 

Clinical Implications: Why This Study Matters

The researchers point to a straightforward recommendation: clinicians shouldn’t evaluate these conditions in isolation. A child referred for autism concerns might also be struggling with ADHD. A child referred for ADHD might have undiagnosed ODD. And ignoring one disorder can undermine treatment for the others.

Evidence-based interventions (behavioral therapy, parent training, school supports, and/or medication) can reduce symptoms across all three diagnoses while improving long-term outcomes, including overall quality of life.

November 21, 2025

What Sleep Patterns Reveal About Mental Health: A Look at New Research

Background:

Sleep is more than simple rest. When discussing sleep, we tend to focus on the quantity rather than the quality,  how many hours of sleep we get versus the quality or depth of sleep. Duration is an important part of the picture, but understanding the stages of sleep and how certain mental health disorders affect those stages is a crucial part of the discussion. 

Sleep is an active mental process where the brain goes through distinct phases of complex electrical rhythms. These phases can be broken down into non-rapid eye movement (NREM) and rapid eye movement (REM). The non-rapid eye movement phase consists of three stages of the four stages of sleep, referred to as N1, N2(light sleep), and N3(deep sleep). N4 is the REM phase, during which time vivid dreaming typically occurs. 

Two of the most important measurable brain rhythms occur during non-rapid eye movement (NREM) sleep. These electrical rhythms are referred to as slow waves and sleep spindles. Slow waves reflect deep, restorative sleep, while spindles are brief bursts of brain activity that support memory and learning.

The Study: 

A new research review has compiled data on how these sleep oscillations differ across psychiatric conditions. The findings suggest that subtle changes in nightly brain rhythms may hold important clues about a range of disorders, from ADHD to schizophrenia.

The Results:

ADHD: Higher Spindle Activity, Mixed Slow-Wave Findings

People with ADHD showed increased slow-spindle activity, meaning those brief bursts of NREM activity were more frequent or stronger than in people without ADHD. Why this happens isn’t fully understood, but it may reflect differences in how the ADHD brain organizes information during sleep. Evidence for slow-wave abnormalities was mixed, suggesting that deep sleep disruption is not a consistent hallmark of ADHD.

Autism: Inconsistent Patterns, but Some Signs of Lower Sleep Amplitude

Among individuals with autism spectrum disorder (ASD), results were less consistent. However, some studies pointed to lower “spindle chirp” (the subtle shift in spindle frequency over time) and reduced slow-wave amplitude. Lower amplitude suggests that the brain’s deep-sleep signals may be weaker or less synchronized. Researchers are still working to understand how these patterns relate to sensory processing, learning differences, or daytime behavior.

Depression: Lower Slow-Wave and Spindle Measures—Especially With Medication

People with depression tended to show reduced slow-wave activity and fewer or weaker sleep spindles, but this pattern appeared most strongly in patients taking antidepressant medications. Since antidepressants can influence sleep architecture, researchers are careful not to overinterpret the changes.  Nevertheless, these changes raise interesting questions about how both depression and its treatments shape the sleeping brain.

PTSD: Higher Spindle Frequency Tied to Symptoms

In post-traumatic stress disorder (PTSD), the trend moved in the opposite direction. Patients showed higher spindle frequency and activity, and these changes were linked to symptom severity which suggests that the brain may be “overactive” during sleep in ways that relate to hyperarousal or intrusive memories. This strengthens the idea that sleep physiology plays a role in how traumatic memories are processed.

Psychotic Disorders: The Most Consistent Sleep Signature

The clearest and most reliable findings emerged in psychotic disorders, including schizophrenia. Across multiple studies, individuals showed: Lower spindle density (fewer spindles overall), reduced spindle amplitude and duration, correlations with symptom severity, and cognitive deficits.

Lower slow-wave activity also appeared, especially in the early phases of illness. These results echo earlier research suggesting that sleep spindles, which are generated by thalamocortical circuits, might offer a window into the neural disruptions that underlie psychosis.

The Take-Away:

The review concludes with a key message: While sleep disturbances are clearly present across psychiatric conditions, the field needs larger, better-standardized, and more longitudinal studies. With more consistent methods and longer follow-ups, researchers may be able to determine whether these oscillations can serve as reliable biomarkers or future treatment targets.

For now, the take-home message is that the effects of these mental health disorders on sleep are real and measurable.