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November 14, 2023
Two new studies, examining entire nationwide populations on opposite sides of the world, have just reported findings on the association between hypertensive disorders of pregnancy (HDP) and subsequent ADHD in off spring. HDP includes chronic hypertension, pre-eclampsia, pre-eclampsia superimposed on chronic hypertension, and gestational hypertension.
According to the Mayo Clinic, Preeclampsia is a pregnancy complication characterized by high blood pressure and signs of damage to another organ system, most often the liver and kidneys. Preeclampsia usually begins after 20 weeks of pregnancy in women whose blood pressure had been normal. Left untreated, it can lead to serious complications for both mother and baby and can be fatal. This range of conditions affects more than one in twenty pregnancies worldwide. HDP hampers permeability of the placenta, which may reduce delivery of blood-borne oxygen and nutrients to the fetus, potentially affecting brain development. ADHD could thus theoretically emerge as a neurodevelopmental outcome.
To what extent is this borne out in national-wide population studies? Both Taiwan and Sweden have single-payer national health insurance systems that systematically track virtually every resident. One study team used the Taiwan National Health Insurance research database to examine a cohort of 877,233 children born between 2004 and 2008. The other study team used the Swedish national registers to explore a cohort of 1,085,024 individuals born between 1987 and 1996.
The Taiwanese study adjusted for the following covariate/confounders: year of birth, fetal sex, paternal age, maternal age, family income, urbanization level, maternal diabetes diagnosis, preterm birth, small for gestational age, and parental psychiatric disorders. The Swedish study adjusted for the calendar year of birth, offspring sex, maternal age, parity, height, body mass index, smoking, presentational diabetes, parental educational level, occupation, and marital status. In the Taiwanese population, children of mothers with hypertensive disorders during pregnancy were about 20% more likely to develop ADHD than those of mothers without such disorders. There was no significant difference between chronic hypertension and pregnancy-induced hypertension/pre-eclampsia.
In the Swedish population, children of mothers with hypertensive disorders during pregnancy were about 10% more likely to develop ADHD than those of mothers without such disorders. But the Swedish study also went a step further. It is incredibly difficult to identify all significant confounding variables. But if you have a large enough study population, one can examine the effect of restricting the analysis to siblings within the same families. In that way, one can control in large measure for familial confounding “ shared environment and heredity. In the subsample of siblings “ 1,279 exposed to HDP versus 1,607 not exposed “ those exposed to outerwear were 9% more likely to develop ADHD, but this outcome was not statistically significant.
Noting the reduced statistical power of the subsample, the authors nonetheless concluded, the magnitude of these associations might be too weak(for ADHD in particular) to be considered an important risk factor at the level of the general population Moreover, in a separate cohort of 285,901 Swedish men born between 1982 and 1992 who attended assessments for military conscription, mildly lower cognitive scores among those exposed to HDP in uteri vanished altogether (mean difference = 0) when limited to comparisons between full siblings (1,917 exposed versus 2,044 not exposed).
Judith S. Brand, Deborah A. Lawlor, Henrik Larsson, Scott Montgomery, "Association Between Hypertensive Disorders of Pregnancy and Neurodevelopmental Outcomes Among Offspring," JAMAPediatrics, published online ahead of print, https://doi.org/10.1001/jamapediatrics.2020.6856.
Kuan-Ru Chen, Tsung Yu, Lin Kang, Yueh-Ju Lien, Pao-Lin Kuo, "Childhood neurodevelopmental disorders and maternal hypertensive disorder of pregnancy," Developmental Medicine & ChildNeurology (2021), published online ahead of print, https://doi.org/10.1111/dmcn.14893.
"Preeclampsia," Mayo Clinic, https://www.mayoclinic.org/diseases-conditions/preeclampsia/symptoms-causes/syc-20355745.
For many ADHD patients, getting properly diagnosed and starting meds is only half the battle. The next step is figuring out the exact right dose. Historically, clinical guidelines have provided scant guidance on this critical step. This lack of direction can inadvertently foster two extremes in clinical practice: therapeutic inertia (settling for a subtherapeutic dose that leaves symptoms undertreated) or uncritical escalation (driving doses higher and higher beyond licensed limits without meaningful benefit).
To clear up this pharmacological gray area, an international team of researchers published the first comprehensive dose-effect network meta-analysis of ADHD medications in The Lancet Psychiatry. By pulling together a massive vault of clinical trial data, they mapped out exactly how efficacy and tolerability shift as doses increase.
Traditional meta-analyses evaluate head-to-head, pairwise data, comparing one drug at a specific dose directly against a placebo. However, this study utilized an advanced Bayesian hierarchical network model using restricted cubic splines.
This mathematical framework allowed the researchers to combine both direct trial data and indirect evidence simultaneously across 113 double-blind randomized controlled trials (RCTs). In total, the study evaluated data from 14,138 children/adolescents and 11,016 adults. By standardizing various formulations into basic equivalents (e.g., converting amphetamines to dextroamphetamine equivalents), they created a clear, unified map of dose ranges.
The study yielded distinct dose-response curves depending on the patient's age and the specific medication class. Rather than a linear trend in which "more medicine equals more benefit," most treatments reach a clear statistical plateau or ceiling.
For Children and Adolescents (under 18)
In the pediatric population, medications hit clear peak efficacy boundaries:
For both amphetamines and guanfacine, escalating the dosage past these points resulted in U-shaped curves, meaning further dose hikes yielded diminishing group-level symptom reduction.
For Adults (18 and older)
Adult profiles showed slightly different trajectories:
The ultimate goal of this landmark analysis is to guide shared decision-making between clinicians, patients, and families. The results send a dual message to the medical community:
A medication's true efficacy hinges on its tolerability, typically measured by how often patients discontinue treatment due to severe side effects. For amphetamines, this dropout risk scales linearly with dosage, notably exceeding placebo in children above 25 mg/day and becoming prominent in adults past 50 mg/day. In contrast, methylphenidate shows no clear dose-dependent dropout risk in pediatric patients, whereas adults face a steep risk curve: increasing the dose from 60 mg/day to 90 mg/day raises the dropout risk from 7.3% to 10.0% for only modest symptom relief. Finally, youth taking guanfacine experience a sharp climb in discontinuation risks, reaching a 9.8% median risk at 4 mg/day before data limitations obscure further trends.
The authors strongly emphasize that these findings represent group averages. Because individual metabolism, genetics, and comorbidities vary widely, some specific patients may legitimately require and tolerate higher off-label doses. However, if an unusually high dose is needed, the study suggests it should prompt a careful clinical pause, either to reassess for co-occurring conditions (like anxiety, autism, or sleep disorders) or to manage realistic expectations regarding what the medication can achieve.
The persistent shortage of ADHD medications has been more than a simple annoyance for patients at the pharmacy; the inconsistent availability of these medications has had deep impacts on the daily lives of those struggling without them. While public discourse has pointed fingers at over-prescribing or at restrictive DEA quotas, a recent economic evaluation in JAMA Health Forum suggests we’ve been looking in the wrong direction for an answer to what is causing this.
The reality of the shortage is less about increased demand and more about a fragile, globalized supply chain that snapped at a critical link.
Debunking the "Quota Myth":
The prevailing narrative suggested that the Drug Enforcement Administration (DEA) was stifling production by refusing to raise quotas. However, the data tells a different story. In 2022, manufacturers collectively met only about 70% of their allotted production quotas.
So we know that the problem wasn't that this DEA quota ceiling was too low. In fact, most manufacturers couldn't even reach it. Even when accounting for exports and domestic retail, production remained significantly below the legal limit. Even if the DEA had doubled its quotas, these medications still likely wouldn't have magically appeared on pharmacy shelves.
The most striking finding in the study is the correlation between the shortage and a sharp decline in the import of raw Active Pharmaceutical Ingredients (APIs). For the past decade, Germany has accounted for over 85% of US amphetamine imports. In 2022, these imports dropped by approximately 36.7%. When the API doesn't arrive at the factory, production for medium and small manufacturers grinds to a halt. Unlike larger pharmaceutical giants, these smaller players often lack the inventory cushion or flexibility to quickly pivot to a new supplier.
When the primary supply of amphetamine-based stimulants (like Adderall) faltered, it triggered a secondary crisis. Patients and clinicians, seeking alternatives, shifted toward lisdexamfetamine (Vyvanse) and methylphenidate (Ritalin/Concerta).
If we view this shortage purely through a regulatory or clinical lens, we miss the underlying cause of the crisis. The pharmaceutical industry has become a victim of its reliance on "just-in-time manufacturing” and highly concentrated sourcing. Because over 30% of APIs for the US market are produced in just one or two facilities globally, the system isn't just inefficient; it’s brittle. We are, in a sense, trapped in a system that prioritizes cost-reduction over the resilience required for public health.
The researchers suggest several policy shifts to prevent a repeat of this supply chain failure:
The ADHD medication shortage wasn't a failure of clinical oversight or a sudden surge in "TikTok-driven diagnoses”, as many have suggested. It was a failure of logistics. It reminds us that the path from a lab in Germany to a patient's hand in the US is far more precarious than we realized.
ADHD is a neurodevelopmental condition rooted in delayed or atypical maturation of the prefrontal cortex (the brain region that governs self-regulation). This maturational lag underlies the hallmark difficulties with attention, hyperactivity, and impulsivity, and also impairs what researchers call executive function: the cognitive toolkit we rely on for working memory, impulse control, mental flexibility, emotional regulation, and the ability to tolerate delays in reward.
The Background:
Standard treatments work through two main routes. Stimulant and non-stimulant medications are considered very safe and effective treatments, but are not without risk of side effects and are not appropriate for every ADHD patient. Behavioral and psychosocial interventions can improve self-regulation and social functioning, but they require sustained effort and produce variable results. These limitations have kept the search for better alternatives active.
One candidate that has drawn growing attention is transcranial direct current stimulation (tDCS). The technique is appealingly simple: a weak electrical current is applied to the scalp through small electrodes, modulating the excitability of neurons in the underlying cortex without requiring surgery, anesthesia, or significant discomfort. Its safety profile and ease of use have made it attractive to researchers.
The Study:
A newly published meta-analysis set out to give the technique its most rigorous test yet, pooling results from randomized controlled trials, including crossover designs, that compared active tDCS against sham stimulation in people with ADHD across all age groups.
The Results:
The findings were consistently null. Across seven trials enrolling 303 participants, tDCS produced no significant reduction in overall ADHD symptom severity compared with sham. Breaking symptoms into their components made no difference: neither hyperactivity/impulsivity nor inattention improved. Turning to executive function, 18 studies with 872 participants found no meaningful gain in inhibitory control, and 12 studies with 506 participants found the same for working memory. Smaller bodies of evidence, including three studies on cognitive flexibility (122 participants) and two on hot executive function, the motivational and emotional dimension of self-regulation (86 participants), similarly came up empty. Variation in outcomes across studies was small to moderate, and there was no evidence of publication bias skewing the picture.
The authors’ conclusion was succinct: tDCS was well tolerated but “did not demonstrate significant overall efficacy for core ADHD symptoms or executive functions.”
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