September 26, 2024

Norwegian Population Study of Adolescents Finds Interpersonal Trauma Much More Likely Than Situational Trauma to Lead to ADHD Diagnosis

Potentially traumatic experiences (PTEs) refer to events where someone is exposed to situations that involve threats to life, serious injury, or danger to themselves or others. These events can include things like accidents, violence, or the death of someone close. PTEs are significant because they can have lasting effects on a person's mental health.

A research team from Norway, working with a collaborator from the U.S., used their country’s universal health care system to study how PTEs affect the mental health of children and adolescents in Hordaland County, which includes the city of Bergen. They wanted to see how experiencing PTEs influenced the likelihood of these young people seeking help from child and adolescent mental health services (CAMHS) or being diagnosed with psychiatric disorders, including ADHD.

In 2012, the study invited all 19,439 teenagers born between 1993 and 1995 in Hordaland County to participate. These teens were 16 to 19 years old at the time. Out of this group, 9,555 teens agreed to let the researchers link their personal data with the National Patient Registry (NPR), which keeps track of health records. There was no significant difference in the types or number of PTEs between those who agreed to this data sharing and those who did not.

After removing participants with incomplete information, the researchers were left with 8,755 teens. These teens’ psychiatric diagnoses, including ADHD, were taken from the NPR. The researchers asked the participants if they had ever experienced specific traumatic events, such as:

  • A serious accident or disaster
  • Violence from an adult
  • Witnessing violence against someone they cared about
  • Unwanted sexual actions
  • The death of someone close to them

If a participant reported experiencing the death of someone close, they were asked to specify who it was (a parent, sibling, grandparent, other family member, close friend, or romantic partner). One limitation of the study was that it did not ask about bullying, which could also be a traumatic experience.

Key Findings

The researchers divided the teens into three trauma groups based on their experiences:

  1. Low Trauma Group (88% of participants): These teens had not experienced anything more traumatic than the death of a grandparent.
  2. Interpersonal Trauma Group (6% of participants): These teens had experienced or witnessed violence, and some had also been exposed to sexual abuse, accidents, or the death of family members.
  3. Situational Trauma Group (6% of participants): These teens had experienced accidents and multiple deaths (including of close friends), but had less exposure to violence.

Other Important Factors

Teens in the situational and interpersonal trauma groups were more likely to see their economic situation as worse than those in the low trauma group. For example, 11% of the situational trauma group and 17% of the interpersonal trauma group considered themselves economically worse off, compared to just 6.1% of the low trauma group. Also, fewer parents of teens in the two higher trauma groups had higher levels of education, which can impact family support and resources.

ADHD and Trauma

After adjusting for gender and parental education, the researchers found that:

  • Teens in the situational trauma group were more than twice as likely to be diagnosed with ADHD compared to those in the low trauma group.
  • Teens in the interpersonal trauma group (who had experienced or witnessed more violence) were more than twice as likely to be diagnosed with ADHD compared to those in the situational trauma group.

The effect was even stronger when comparing the interpersonal trauma group to the low trauma group. Teens in the interpersonal trauma group were almost five times more likely to be diagnosed with ADHD than those in the low trauma group.

Study Limitations

One limitation of the study is that while the researchers acknowledged that sex and socioeconomic status (SES) are important factors in the relationship between trauma and psychiatric disorders, they did not directly adjust for SES. However, they did indirectly account for it by considering the education levels of the parents, which is closely related to SES.

Conclusion

The study showed that adolescents who experience more interpersonal trauma (like violence or sexual abuse) are at a significantly higher risk of being diagnosed with ADHD. The findings suggest that it’s important to pay special attention to teens who experience both situational and interpersonal traumas, especially those exposed to interpersonal violence. Early intervention and support could be key to helping these adolescents manage their mental health.

Annika Skandsen, Sondre Aasen Nilsen, Mari Hysing, Martin H. Teicher, Liv Sand, and Tormod Bøe, “Associations Between Distinct Trauma Classes and Mental Health Care Utilization in Norwegian Adolescents: A National Registry Study,” Child Psychiatry & Human Development (2024), https://doi.org/10.1007/s10578-024-01671-9.

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South Korean Nationwide Population Study: Prenatal Exposure to Acid-suppressive Medications Not Linked to Subsequent ADHD

Acid-suppressive medications, including proton pump inhibitors (PPIs) and histamine-2 (H2) receptor antagonists, are often prescribed during pregnancy to treat heartburn and gastroesophageal reflux disease. 

Research shows changes in the gut microbiome can negatively affect neurodevelopment. Since acid-suppressive medications alter gut microbiota, maternal use during pregnancy may impact offspring’s neurodevelopment. Because PPIs and H2 receptor antagonists readily cross the placental barrier, they could potentially influence fetal neurodevelopment.  

The link between prenatal exposure to acid-suppressive medications and major neuropsychiatric disorders is not well understood. With the use of these medications during pregnancy rising, it is important to assess their impact on children's long-term neurodevelopment. This study examined whether maternal use of acid-suppressive drugs is associated with increased risk of neuropsychiatric disorders in children, using a large, nationwide birth cohort from South Korea. 

South Korea operates a single-payer health insurance system, providing coverage for over 97% of its citizens. The National Health Insurance Service (NHIS) maintains a comprehensive database with sociodemographic details, medical diagnoses, procedures, prescriptions, health examinations, and vital statistics for all insured individuals. 

A Korean research team analyzed data from over three million mother-child pairs (2010–2017) to assess the risks of prenatal exposure to acid-suppressing medications. They applied propensity scoring to adjust for maternal age, number of children, medical history, and outpatient visits before pregnancy, to minimize confounding factors. That narrowed the cohort to just over 800,000 pairs, with half in the exposed group. 

With these adjustments, prenatal exposure to acid-suppressing medications was associated with 14% greater likelihood of being subsequently diagnosed with ADHD. 

Yet, when 151,737 exposed births were compared to the same number of sibling controls, no association was found between prenatal exposure and subsequent ADHD, which suggests unaccounted familial and genetic factors influenced the preceding results. 

The Take-Away:

Evidence of these medications negatively affecting pregnancies is mixed, mostly observational, and generally reassuring when these medications are used appropriately. Untreated GERD and gastritis, however, have known risks and associations with the development of various cancers. With no evidence of an association with ADHD (or for that matter any other neuropsychiatric disorder), there is no current evidence-based reason for expectant mothers to discontinue use of acid-suppressing medications.  

February 6, 2026

The 'Medication Tolerance' Myth in ADHD: What the Evidence Actually Says

For years, a persistent concern has shadowed the treatment of Attention-Deficit/Hyperactivity Disorder (ADHD): Does the medication eventually stop working? Patients often report that their symptoms seem to return despite consistent use, leading to "dose escalation" or "medication holidays." A new systematic review from Sam Cortese’s team  published in CNS Drugs finally puts these concerns to the test by synthesizing decades of empirical research.

Before diving into the findings, you must understand two often-confused phenomena:

  • Tachyphylaxis (Acute Tolerance): A rapid decrease in response to a drug, often occurring within a single day (24 hours).
  • Tolerance: A gradual reduction in responsiveness over long-term exposure, requiring higher doses to achieve the original effect.

The review analyzed 17 studies covering over 10,000 individuals, and the results provide a much-needed reality check for the clinical community.

The researchers found preliminary evidence that acute tolerance (tachyphylaxis) can occur within a 24-hour window.

  • Subjective Effects: Studies showed that "drug liking" or feelings of euphoria from stimulants often peak and fade faster than the actual drug concentration in the blood.
  • Clinical Impact: This phenomenon is why some older, flat-release formulations were less effective than modern "ascending" delivery systems (like OROS-methylphenidate), which are designed to overcome this daily dip in efficacy.

The most important finding is that tolerance does not commonly develop to the therapeutic effects of ADHD medication in the long term. In one landmark study following children for up to 10 years, only 2.7% of participants lost their response to methylphenidate without a clear external explanation.  Doses, when adjusted for natural body growth, remained remarkably stable over years of treatment.

Consistent with the lack of therapeutic tolerance, the body does not become tolerant to the physical side effects of stimulants.  Increases in heart rate and blood pressure typically persist for as long as the medication is taken.  This underscores why clinicians must continue monitoring cardiovascular health throughout the entire duration of treatment.

If it’s Not Tolerance, What Is It?

If "tolerance" isn't real, why do some patients feel their medication is failing? The review suggests clinicians look at these alternative explanations:

  1. Natural Symptom Fluctuations: ADHD is not a static condition; symptoms naturally wax and wane over time regardless of treatment.
  2. Limited Compliance: Missed doses or inconsistent timing are often the real culprits behind "failing" efficacy.
  3. Life Events & Transitions: New jobs, academic pressures, or stressful life changes can increase the "functional demand" on a patient, making their current dose feel insufficient.
  4. Co-occurring Conditions: The emergence of anxiety, depression, or substance use disorders can mask or mimic a return of ADHD symptoms.

Why This Matters

These results provide clinicians the confidence to tell patients that their medication is unlikely to "wear out" permanently. Rather than immediately increasing a dose when symptoms flare, the first step should be a "clinical deep dive" into the patient's lifestyle, stress levels, and adherence.

For researchers, the review highlights a major gap: most existing studies are small, dated, or of low quality. There is a dire need for robust, longitudinal studies that track both the brain's response and the patient's environment over several years.

For people with ADHD, while your body might get "used to" the initial "buzz" of a stimulant within hours, its ability to help you focus and manage your life remains remarkably durable over the years.

Population Study Finds Association Between Extended Methylphenidate Use By Children and Subsequent Obesity

South Korean Nationwide Population Study Finds Association Between Extended Methylphenidate Use By Children and Subsequent Obesity–Little to No Effect on Adult Height

South Korean Nationwide Population Study Finds Association Between Extended Methylphenidate Use By Children and Subsequent Obesity–Little to No Effect on Adult Height

The Background:

Concerns remain about how ADHD and methylphenidate (MPH) use might affect children's health and growth, and especially how it may affect their adult height. While some studies suggest disrupted growth and a possible biological mechanism, the impact of ADHD prevalence and MPH use is still unclear. Children with ADHD may develop unhealthy habits – irregular eating, low physical activity, and poor sleep – that can contribute to obesity and reduced height. MPH’s appetite-suppressing effect can lead to skipped meals or overeating. Since growth hormone is mainly released during deep sleep, chronic sleep deprivation could plausibly slow growth and impair height development; however, a clear link between ADHD, MPH use, overweight, and shorter stature has never been firmly established. 

The Study:

South Korea has a single payer health insurance system that covers more than 97% of its population. A Korean research team used the National Health Insurance Service database to perform a nationwide population study to explore this topic further. 

The study involved 34,850 children, of whom 12,866 were diagnosed with ADHD. Of these children, 6,816 (53%) had received methylphenidate treatment, while 6,050 (47%) had not. Each patient with ADHD was precisely matched 1:1 by age, sex, and income level to a control participant without ADHD. The sex ratio was comparable in all groups.The team used Body Mass Index (BMI) as an indicator of overweight and obesity. 

The Results: 

The researchers found that being diagnosed with ADHD was associated with 50% greater odds of being overweight or obese as young adults, and over 70% greater odds of severe obesity (BMI > 30) compared to matched non-ADHD controls, regardless of whether or not they were medicated.

Those diagnosed with ADHD, but not on methylphenidate, had 40% greater odds of being overweight or obese, and over 55% greater odds of becoming severely obese, relative to matched non-ADHD controls. 

Methylphenidate users had 60% greater odds of being overweight or obese, and over 85% greater odds of becoming severely obese, relative to matched non-ADHD controls. 

There were signs of a dose-response effect. Less than a year’s exposure to methylphenidate was associated with roughly 75% greater odds of becoming severely obese, whereas exposure over a year or more raised the odds 2.3-fold, relative to matched non-ADHD controls. Using MPH increased the prevalence of overweight from 43.2% to 46.5%, with a greater prevalence among those using MPH for more than one year (50.5%).

It is important to note that most of this effect was from ADHD itself, with methylphenidate only assuming a predominant role in severe obesity among those with longer-term exposure to the medicine. 

As for height, children with ADHD were no more likely to be short of stature than matched non-ADHD controls. Being prescribed methylphenidate was associated with slightly greater odds (7%) of being short of stature, but there was no dose-response relationship. 

Conclusion: 

The team concluded, “patients with ADHD, particularly those treated with MPH, had a higher BMI and shorter height at adulthood than individuals without ADHD. Although the observed height difference was clinically small in both sexes and age groups, the findings suggest that long-term MPH exposure may be associated with growth and body composition, highlighting the need for regular monitoring of growth.” They also point out that “Despite these findings, the clinical relevance should be interpreted with caution. In our cohort, the mean difference in height was less than 1 cm (eg, maximum −0.6 cm in females) below commonly accepted thresholds for clinical significance.”  Likewise, increases in overweight/BMI were small. 

One problem with interpreting the BMI/obesity results is that some of the genetic variants that cause ADHD also cause obesity.  If that genetic load increases with severity of ADHD than the results from this study are confounded because those with more severe ADHD are more likely to be treated than those with less severe ADHD.

Due to these small effects along with the many study limitations noted by the authors, these results should be considered alongside the well-established benefits of methylphenidate treatment.

February 2, 2026