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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.”
Francesca Anns, Stephanie D’Souza, Conrad MacCormick, Brigit Mirfin-Veitch, Betony Clasby, Nathan Hughes, Warren Forster, Eden Tuisaula, and Nicholas Bowden, “Risk of Criminal Justice System Interactions in Young Adults with Attention-Deficit/Hyperactivity Disorder: Findings From a National Birth Cohort,” Journal of Attention Disorders (2023), 1-11, https://doi.org/10.1177/10870547231177469.
Children with disabilities are known to be at heightened risk of violence compared to their non-disabled peers. To what extent does this hold true for ADHD?
Denmark has a single-payer health insurance system through which health data about virtually the entire population can be cross-referenced with population, crime, welfare, and other registers through unique individual person numbers.
A Danish study team accessed national registers to examine the relationship between ADHD and criminal victimhood among nine yearly birth cohorts totaling more than 570,000 children and adolescents.
Of these, 557,521, among them 12,040 with ADHD, were not reported as being exposed to violence, and 12,830, among which 1,179 with ADHD, were exposed to violence.
From the raw data, children and adolescents with ADHD were more than four times as likely to be exposed to violence than their typically developing peers.
The team then adjusted for other disabilities, family risk factors, gender, birth year, and ethnic background.
With these confounders out of the way, children and adolescents with ADHD remained more than twice as likely to be exposed to violence than their typically developing peers.
To place this outcome in further perspective:
Certain family risk factors further aggravated the odds:
Perhaps surprisingly, substance abuse by family members had no effect whatsoever after adjusting for confounders.
Child abuse includes any of the following inflicted on a minor under 18 years old: physical or emotional harm, sexual abuse, or neglect.
It is known to be associated with environmental factors such as poverty, parents or neighbors with a history of violence, and gender inequality.
Chronic mental disorders in minors are also associated with child abuse. To what extent, if any, might that be true of ADHD?
Taiwan has a single-payer national health insurance system that covers more than 99.6% of all residents, enabling nationwide population studies.
A local research team used data from almost two million Taiwanese in their country’s National Health Insurance Research Database (NHIRD) spanning 15 years (2000-2015) to carry out a matched-cohort study.
All diagnoses of ADHD were made by board-certified specialists such as psychiatrists, pediatricians, neurologists, or physiatrists with a specialty in child and adolescent development.
3,540 children and adolescents between 6 and 18 years old with a diagnosis of ADHD were matched on a one-to-three basis with 10,620 peers from the NHIRD without an ADHD diagnosis.
The team adjusted for age, gender, location of residence (Northern, Central, Southern, and Eastern Taiwan), urbanization level of residence, level of hospitals as medical centers, and monthly insured premium. They further adjusted for comorbid conditions: intellectual disability, autistic disorder/pervasive developmental disorder, conduct disorder (CD)/oppositional defiant disorder (ODD), other developmental disorders, childhood emotional disorder, Tourette syndrome/tics disorders, and involuntary urination and defecation.
Overall, children and adolescents with an ADHD diagnosis were 1.8 times as likely to be abused as those without an ADHD diagnosis.
Unmedicated children and adolescents with an ADHD diagnosis were three times more likely to be abused. ADHD medication cut that risk in half.
That held true whether the medication used was methylphenidate or atomoxetine. Methylphenidate appeared to be slightly more effective than atomoxetine, and the combination of methylphenidate and atomoxetine slightly more effective yet, but these differences were not statistically significant.
The team concluded, “The results support that pharmacotherapy may attenuate the risk of child abuse in ADHD patients.”
Taiwan's National Health Insurance program is a single-payer system that covers 99.6% of the island's 23 million residents. It includes family relationships.
This enabled a Taiwanese study team to examine the comorbidity of psychiatric disorders among close relatives in the entire population over eleven years, beginning at the start of 2001 and concluding at the end of2011.
For greater certainty of diagnosis, only persons twice diagnosed with the same psychiatric disorder were included as index individuals. There were 431,887 index patients, 152,443 of whom were ADHD index patients.
These index patients were then compared with all of their first-degree relatives (FDRs): parents, children, siblings, and twins. This produced 1,017,430 patient-FDR pairs, of which 401,301 were ADHD patient-FDR pairs.
Next, four controls were matched by age, gender, and type relative to each case, resulting in 4,069,720 control pairs.
After adjusting for age, gender, urbanization, and income level, ADHD patients were seven times more likely than controls to have first-degree relatives with ADHD. They were also seven times more likely to have FDRs with major depressive disorder, four times more likely to have FDRs with autism spectrum disorder, twice as likely to have FDRs with bipolar disorder, and 80%more likely to have FDRs with schizophrenia.
A new study from Japan suggests that infants born with craniosynostosis are significantly more likely to be diagnosed with ADHD later in childhood. Craniosynostosis is a condition in which the bony plates of the skull fuse prematurely, leading to increased intracranial pressure.
The Background:
Craniosynostosis affects roughly one in every 2,000 births. When the skull’s natural seams close prematurely, it can restrict brain growth and increase intracranial pressure, potentially reducing blood flow to the brain. Because the condition is relatively rare, it has been difficult to study at scale until now.
The Study:
To overcome this, researchers tapped into a large Japanese insurance database compiled by JMDC, Inc., which holds records on around 20 million people, or about 15% of Japan’s population. Drawing on two decades of data, the team tracked over 338,000 mother-child pairs. Children with related genetic syndromes or chromosomal conditions such as Down syndrome were excluded to keep the focus on craniosynostosis itself.
Of the children studied, around 1,145 had craniosynostosis, and 7,325 were diagnosed with ADHD. After accounting for factors like sex, birth year, maternal age, mental health history, pregnancy infections, and birth complications, children with craniosynostosis were found to have roughly 2.4 times the risk of a subsequent ADHD diagnosis compared to those without it.
To test whether shared family genetics or home environment might be driving the association rather than the skull condition itself, the researchers conducted a separate analysis among siblings. The elevated risk remained at 2.2 times. The consistency of the finding across both analyses strengthens the case for a genuine biological link.
The Results:
The results point to raised intracranial pressure and restricted cerebral blood flow as plausible mechanisms, though the study’s observational design means causation cannot be confirmed. Ultimately, these findings highlight the need for proactive, long-term care strategies for those born with craniosynostosis. By establishing a solid link between premature skull fusion and a significantly higher risk of ADHD, the research demonstrates that medical care for this condition should not end once the skull's physical structure is addressed.
The Takeaway:
Pediatricians, neurologists, and parents can use this data to implement early, routine behavioral and developmental screening for these children as they grow. This additional support would ensure that those who do develop ADHD can receive timely interventions, educational aids, and therapies, ultimately improving their long-term developmental outcomes.
Children and adolescents with ADHD come into contact with child welfare services (CWS) far more often than their peers. There are many contributing factors to consider, including the fact that hyperactivity and impulsivity frequently lead to behaviors that are considered disruptive and cause academic and social difficulties. Many of these children are also growing up in households marked by parental conflict and/or single-parent arrangements. All of these circumstances can compound vulnerability and, historically, increase the likelihood of CWS involvement.
Background:
In Norway, Child Welfare Services operate at the municipal level and are legally required in every local authority. Their scope spans investigation, family support, and, where necessary, out-of-home placement and ongoing monitoring. Grounds for intervention include abuse, neglect, behavioral or psychosocial difficulties, and inadequate care-giving. Norwegian CWS works closely with health, education, and social services and places a strong emphasis on keeping families together. Compared with systems in countries such as the United States, Poland, Romania, and the Czech Republic, the Norwegian approach sets a lower bar for intervention and leans toward home-based support, while setting a higher bar for out-of-home placements. This model is shared by other Nordic countries, as well as Germany and the United Kingdom.
Research into whether ADHD medication affects child welfare caseloads is remarkably sparse. A single Danish study previously found that medication treatment accounted for much of an observed decline in foster care cases, but no study had examined medication’s broader impact on CWS involvement, covering both supportive interventions and out-of-home placements.
Norway’s universal single-payer health system and comprehensive national registers make population-wide research of this kind feasible. Drawing on these resources, a Norwegian research team set out to test whether ADHD medication reduces children’s contact with CWS and their need for out-of-home placement.
The Study:
This study included all 5,930 children and adolescents aged 5 to 14 who received a clinical ADHD diagnosis from Child and Adolescent Mental Health Services between 2009 and 2011. Each was followed for up to 4 years post-diagnosis, the upper age limit being 18, at which point CWS jurisdiction ends. This group was compared with more than 53,000 peers who had no CWS contact during the same period.
The results showed a meaningful, though not dramatic, association between medication and reduced CWS contact. At one year, treated children had approximately 7% fewer contacts with CWS; by two years, that figure had risen to around 12%. The effect then narrowed, settling at roughly 7–8% reductions at the three- and four-year marks.
The picture for out-of-home placements is considerably less convincing. The research team highlighted a 3% reduction at two-year follow-up, but this finding barely crossed the threshold of statistical significance, and no effect was observed at the one-, three-, or four-year follow-up points.
The Take-Away:
The authors concluded that pharmacological treatment for ADHD is associated with reductions in both supportive CWS services and out-of-home placements among children affected by clinicians’ prescribing decisions in Norway. A more cautious reading of the same data, however, would emphasize an overall reduction in CWS contact of roughly 8%, while treating the out-of-home placement finding as, at best, inconclusive.
Stimulant medications, such as methylphenidate (Ritalin) and amphetamines (Adderall), are among the most widely prescribed drugs in the world. In the United States alone, prescription rates have climbed more than 50% over the past decade, driven largely by growing awareness of ADHD in both children and adults. Yet stimulants also have a long history of non-medical use, and concerns about their psychological risks persist among patients, families, and clinicians alike.
Two major studies now offer the clearest picture yet of what that risk actually looks like, and who it may affect.
The Background:
Before turning to the research, it helps to understand the landscape. A notable share of stimulant users misuse their medication: roughly one in four takes it in ways other than prescribed, and about one in eleven meets criteria for Prescription Stimulant Use Disorder (PSUD). Counterintuitively, most people with PSUD aren’t obtaining drugs illicitly — they’re misusing their own prescriptions.
This distinction between therapeutic and non-therapeutic use turns out to be critical when evaluating psychosis risk.
The Study:
A comprehensive meta-analysis by Jangra and colleagues pooled data across more than a dozen studies to compare psychotic outcomes in people using stimulants therapeutically versus non-therapeutically. The contrast was striking.
Among therapeutic users (more than 220,000 individuals taking stimulants at prescribed doses under medical supervision), psychotic episodes occurred in roughly one in five hundred people. When symptoms did appear, they typically emerged after prolonged treatment or in individuals with pre-existing psychiatric vulnerabilities, and they usually resolved when the medication was stopped.
Among non-therapeutic users (over 8,000 participants across twelve studies, many using methamphetamine or high-dose amphetamines), nearly one in three experienced psychotic symptoms. These episodes tended to be more severe, involving persecutory delusions and hallucinations, with faster onset and a greater likelihood of recurrence or persistence.
The biology underlying this difference is well understood. When stimulants are taken orally at guideline-recommended doses, they produce moderate, gradual changes in neurotransmitter activity central to attention and executive functions. The brain tolerates these changes relatively well. Non-therapeutic use, by contrast, often involves much higher doses that are frequently delivered through non-oral routes such as injection or smoking. This produces a rapid, excessive surge in dopamine activity, which is precisely the neurochemical pattern associated with psychotic symptoms.
The takeaway here is not that therapeutic stimulant use is risk-free, but that risk is strongly modulated by dose, route of administration, and individual psychiatric history. Clinicians are advised to monitor patients with pre-existing mood or psychotic disorders, particularly carefully.
A Nationwide Study Focuses on Methylphenidate Specifically:
Where the meta-analysis cast a wide net, a large-scale population study by Healy and colleagues drilled into a specific and clinically pressing question: does methylphenidate (the most commonly prescribed ADHD medication, also known as Ritalin) increase the risk of developing a psychotic disorder?
To find out, the researchers analyzed Finland's national health insurance database, tracking nearly 700,000 individuals diagnosed with ADHD. Finland's single-payer system made this kind of comprehensive, long-term tracking possible in a way that fragmented healthcare systems rarely allow.
Critically, the team adjusted for a range of confounding factors that have clouded previous research, including sex, parental education, parental history of psychosis, and the number of psychiatric visits and diagnoses prior to the ADHD diagnosis itself (a proxy for illness severity). After these adjustments, they found no significant difference in the risk of schizophrenia or non-affective psychosis between patients treated with methylphenidate and those who remained unmedicated. This held true even among patients with four or more years of continuous methylphenidate use.
The Take-Away:
When considered together, these studies offer meaningful reassurance without encouraging complacency.
For patients and families weighing ADHD treatment, the evidence suggests that methylphenidate used as prescribed does not increase psychosis risk, even over years of use. The rare cases of stimulant-associated psychosis in therapeutic settings are typically linked to high doses, pre-existing vulnerabilities, or both, and tend to resolve with discontinuation.
For clinicians, the findings reinforce the importance of baseline psychiatric assessment before initiating stimulant therapy, ongoing monitoring in patients with mood or psychotic disorder histories, and clear patient education about the risks of dose escalation or non-oral use.
The picture that emerges is one of a meaningful distinction between a medication used carefully within its therapeutic window and a drug misused outside of it. This distinction matters enormously when communicating risk to patients, policymakers, and the public.
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