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March 5, 2022
Persons with ADHD have known to have high rates of psychiatric comorbidities. There is also growing evidence of somatic (non-psychiatric) comorbid disorders among youths with ADHD, such as metabolic syndrome (which can lead to type 2 diabetes) and chronic inflammation (such as asthma and allergic rhinitis). Much less is known, however, about comorbid conditions in adults with ADHD.
An international team of researchers looked for indicators of comorbid conditions in a nationwide cohort study using Swedish national registers. The target population was Swedish residents between the ages of 18 and 64 in 2013 and more specifically those who had been prescribed ADHD medication. They identified over 41,000 individuals who met these criteria, including over twenty thousand young adults aged 18-29 years, over sixteen thousand middle-aged adults aged 30-49 years, and over four thousand older adults aged 50-64. The remainder of the overall cohort were used as controls.
Young adults receiving ADHD medications were four times as likely to also be receiving somatic medications, and older adults were seven times as likely. The highest rate of co-medication -roughly five times more frequent than among controls - was for respiratory system medications. The second most common was for alimentary tract and metabolic system medications, with odds over four times higher than for controls. Cardiovascular system medications were the next most common, with odds among young adults receiving ADHD medications over four times those of controls, though reducing with age to being twice as common in older adults with ADHD. Patterns were similar among men and women.
Adults receiving ADHD medications were far more likely to also be receiving other psychotropic medications. Middle-aged adults were 21 times as likely to be dispensed such medications as controls, older adults eighteen times more likely, and younger adults fifteen times more likely.
For young adults prescribed ADHD medications, the most prevalent co-prescriptions were for addictive disorders, which were dispensed at over 26 times the rate for controls. For middle-aged and older adults, on the other hand, the most prevalent co-prescriptions were for antipsychotics, which were likewise dispensed at over 26 times the rate for controls. Results remained consistent for individuals who had an ADHD diagnosis in addition to an ADHD prescription.
In addition, individuals receiving ADHD medications were also on average taking more types of prescriptions, rising from 2.5 classes of medications at age 18 to five classes at age 64. For controls, the equivalent numbers were 0.9 types of medications at age 18, rising to 2.7 at age 64.
Looking at specific somatic medications prescribed, those for respiratory conditions were ones typically prescribed for asthma and allergic reactions, reinforcing a previously known association. Insulin preparations also had high rates of co-prescription, again further confirming the known association with obesity and diabetes.
On the other hand, the most commonly dispensed alimentary tract and metabolic system medications included proton pump inhibitors, typically prescribed for gastric/duodenal ulcers and gastroesophageal reflux disease. Sodium fluoride, prescribed to prevent dental caries, was also prominent. Neither of these is an established association and warrants further exploration.
Turning to psychotropic medications, the most frequent prescriptions were with drugs used to treat addictive disorders and with antipsychotics. Rates of opioid co-prescription were also notably high, a source of concern given the higher proclivity of persons with ADHD to substance use disorders.
Le Zhang, AndreasReif, Ebba Du Rietz, Tyra Lagerberg, Agnieszka Butwicka, Brian M. D'Onofrio, Kristina Johnell, Nancy L. Pedersen, Henrik Larsson, and Zheng Chang, "Comedicationand Polypharmacy With ADHD Medications in Adults: A Swedish Nationwide Study," Journal of Attention Disorders (2020),https://doi.org/10.1177/1087054720923725.
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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