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ADHD Explained

By Anna Witkin |
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Considering that global prevalence estimates range from 5-10%, ADHD is remarkably poorly understood and vaguely described. One of the key difficulties in defining ADHD is that the primary symptoms of impulsivity, distraction, and restlessness are experienced by many adults and virtually all children to varying degrees. Is ADHD truly a neurodevelopmental disorder or are we pathologizing children who exhibit normal childhood traits?

ADHD Prevalence Estimates Range From 5-10%

While children diagnosed with ADHD have been found to be at a higher risk for adverse outcomes such as substance misuse, poor academic performance, and interaction with law enforcement, it is unclear to what extent the root cause is intrinsic or extrinsic. It is likely some combination of being forced to function in an environment to which they are poorly suited and being innately predisposed.

These distinctions are important to consider as there is real harm in labeling up to 10% of children fundamentally and inherently defective. Before delving into the minutia of diagnostic and treatment criteria, parents and providers alike should step back and remember that different does not mean inferior, and society benefits from neurological diversity.

However, it must be noted that certain combinations of traits can be advantageous in some environments and disadvantageous in others. In the hypercompetitive world of the American education system, kids with ADHD face significant challenges which may cause considerable distress. It is incumbent upon healthcare providers, parents, and teachers to assist and support these children as necessary without medicalizing their personality or development.

What is ADHD?

In this context, we can now consider what ADHD is and how it may be treated. ADHD can reasonably be defined as a behavioral condition that affects attention, hyperactivity, or impulsivity. It should, however, be noted that ADHD exists on a broad spectrum of severity. It is also essential to distinguish between the definition, diagnostic criteria outlined by the DSM-V, and diagnostic standards used by practitioners.

ADHD Is a Behavioral Condition That Affects Attention, Hyperactivity, or Impulsivity

ADHD Symptoms

Traits

General Symptoms

Symptoms Seen Ages 13 and Above

Inability to control attention

Hyper-focus

Unfinished tasks

Lost homework

Sensitivity to noises / smells

Lost belongings

Under-achieving

Failure to complete homework

Chronically late

Rigidity regarding studying environment

Hyperactivity

Trouble sleeping

Fidgeting

Movement without purpose

Talking constantly

Trouble sitting still

Losing / breaking phone

Needing frequent breaks from academic work

Impulsivity

Hurting others

Accidental injuries

Interrupting

Trouble maintaining friendship

Inability to delay gratification

“No filter” in conversation

Car accidents / tickets

Engaging in high-risk behaviors

Self-harm

Other

Time blindness

Procrastination

Inflexibility

 

The above chart outlines some of the most common symptoms of ADHD across all ages and those specific to older children and adolescents. It must be emphasized that while many of us can relate to portions of this list of symptoms, that does not mean we all have ADHD. The number, frequency, severity, and persistence of symptoms is what determines if the threshold is met for a diagnosis of ADHD. Most critically, the symptoms must reach a level that interferes with daily functioning. This may take the form of a bright child not passing their classes because they never turn in homework, or a talented athlete being benched because they are distracted by the crowd and lose sight of the ball. Prompt and accurate diagnosis is the first step in preventing this loss of potential.

ADHD Testing

To meet DSM-V criteria for ADHD, an individual must exhibit symptoms for at least 6 months and in at least 2 different settings. If under the age of 17 there must be at least 6 of 17 symptoms present, while only 5 of 17 are required if over 17. These symptoms are grouped into categories: inattentive, hyperactive, or impulsive. Importantly, these symptoms must present before age 12 (regardless of the age at time of diagnosis), and must cause functional impairment (i.e. social, academic, or occupational). They also must not be attributable to other factors such as substance use or mood disorder.

Trained professionals may diagnose ADHD by observation of behavior and analysis of questionnaires completed by longer-term observers (often parents or teachers). Psychoeducational testing (often called neuropsychological testing) can be a valuable adjunct to diagnosis, although there is no single test or profile of test results that is an entirely reliable indicator of ADHD. Testing can be conducted in person or via telehealth, and professional organizations have concluded these options are equally reliable in producing meaningful and valid results.  Although physicians sometimes diagnose ADHD by observing a patient and speaking with family members, this is generally considered insufficient for formal diagnosis and should not be the sole basis for treatment.

ADHD Meaning

A common misconception is that those with the diagnosis are unable to focus on anything; the fundamental issue in ADHD is rather one of difficulty regulating attention, and these individuals often can focus with great intensity (sometimes bordering on obsession) on tasks that interest them, but can struggle immensely to attend to those that do not. Their capacity to hyper focus can in fact be an asset if they are allowed to find and pursue what they are passionate about.  

A Common Misconception is That Those With the Diagnosis are Unable to Focus on Anything

It is also important to note that an individual can be diagnosed with either the Impulsive/ Hyperactive subtype or the Inattentive subtype and there is an inherent heterogeneity to the diagnosis. Even within each subtype individuals can present very differently. There has been a recent focus on the differences in presentation between boys and girls with ADHD. Furthermore, the course of symptomatology is highly variable between individuals and impossible to predict. While for some symptoms regress entirely in adulthood, others continue to struggle throughout their life. These complexities and variabilities challenge the diagnostic process and likely result in overdiagnosis in many populations and underdiagnosis in others.

ADHD in Women

ADHD has traditionally been believed to be much more common in boys than girls, but there is growing concern that girls are being vastly underdiagnosed and thus undertreated. Young boys may be diagnosed more often in part because they tend to present with the hyperactive / impulsive subtype, which results in disruptive behaviors that prompt referrals. Girls more often have the inattentive type of ADHD and may be underperforming or struggling in quieter ways. Furthermore, girls and women are more likely to internalize their troubles leading to symptoms of anxiety and depression, which can lead to diagnoses of mood disorders while obscuring the signs of underlying ADHD.

Adult ADHD

While ADHD has long been considered a disorder of childhood, recent data suggests that roughly one-third of children with ADHD continue to meet diagnostic criteria through adulthood, while around 65% still experience significant symptoms (Young et al., 2020, p. 2). Perhaps the prevalence of adult ADHD has been underestimated because of the inherent difficulties in its diagnosis. Firstly, due to their neurocognitive maturity, adults are less likely to be hyperactive and are more likely to display features of the subtler inattentive type of ADHD (Zalsman and Shilton, 2016, p. 71). Furthermore, the symptoms of ADHD can be difficult to identify in adults as they may be masked by coping mechanisms developed over many years. Thus, adult ADHD often presents with symptoms of anxiety and depression secondary to their struggle with untreated ADHD.

Eating Disorders and ADHD

It has recently become apparent that there is a significant correlation between ADHD and eating disorders, with ADHD youth being roughly six times as likely to be diagnosed with an eating disorder as their peers without ADHD (Curtin et al., 2013, p. 195). Possibly as a result of increased impulsivity, individuals with ADHD are especially likely to develop disorders involving binge eating, namely bulimia nervosa and binge eating disorders (Ziobrowski et al., 2018, p. 53). Identification of eating disorders in young people with ADHD is important as it may have a significant bearing on treatment decisions.

ADHD Medication

Recent trends in ADHD diagnosis make it abundantly clear that diagnostic procedures are inconsistent at best and systematically flawed at worst. Prevalence of ADHD in children and adolescents has shot up an alarming 41% in the past decade, and by high school it is estimated that one in five boys have been diagnosed (Hinshaw, 2018, p. 294). Given the improbability that this represents a true increase in prevalence and considering that ADHD could hardly be considered a disorder if it affected 20% of boys, we are left with the inevitable conclusion that rampant overdiagnosis is occurring.

Recent Trends in ADHD Diagnosis Make it Abundantly Clear That Diagnostic Procedures are Inconsistent at Best and Systematically Flawed at Worst

Further suggestive of error-prone diagnostic practices are consistent findings that the youngest children in each grade are considerably more likely to be diagnosed with ADHD than their older peers (Kazda et al., 2021, p. 4). This finding suggests that many children are being diagnosed with ADHD who are simply being asked to perform beyond their neurocognitive maturity, and that this may be a driving force in the apparent rise in prevalence.

CDC surveys have found that the percentage of children under 17 who have ever received an ADHD diagnosis varies dramatically by region of the country. Some southern states reach rates as high as 16.6%, which is roughly three times that in most western states. It is illogical to assume that these differences are due to massive variation in prevalence of ADHD by state, so these findings must represent highly inconsistent practices in diagnosis. Similar inconsistencies have been found in stimulant dispensing practices for the treatment of ADHD: rates reached 13.6 per 100 in Alabama, and only 1.0 per 100 in Hawaii (Board et al., 2020, p. 5).

 CDC Surveys Have Found That the Percentage of Children Under 17 who Have Ever Received an ADHD Diagnosis Varies Dramatically by Region of the Country

The astronomical rise in the rates of ADHD diagnoses, psychostimulant prescription, and non-medical stimulant abuse on both the national and global scale demands a critical examination of diagnostic criteria and indications for medical treatment. As of 2007, worldwide prevalence of ADHD has been estimated at 5.29% in children and 4.4% in adults (Carolan, 2022, p. 315). A 2020 study found that roughly 13% of adults between 18 and 29 years of age used prescription stimulants within the past year, and estimated that 16 million US adults and 2.8 million US children took prescription stimulants (Board et al., 2020, p2). Recent estimates have placed the rate of nonmedical prescription stimulant use among US college students at an alarming 25% (Carolan, 2022, p. 315), while approximately half of all 10–18-year-olds in the US have participated in prescription stimulant diversion either by receiving diverted medications or diverting their own prescription (Board et al., 2020, p. 3).

Group 10709

Faced with such staggering numbers, physicians and mental health professionals must now make a concerted, unified effort to understand the complex landscape within which psychostimulants are used and abused. Toward this end, the following will address some of the key facets of the most commonly prescribed stimulants for ADHD: amphetamines, methylphenidate, and lisdexamphetamine. We must consider not only the evidence amassed over the 70-plus year history of these compounds, but also the weight of the still significant unknowns and the caution necessitated by the unanswered questions that remain.

History of ADHD Medication and Treatment

Stimulants, the class of compounds that includes amphetamines (Adderall), methylphenidate (Ritalin), caffeine, methamphetamine, and cocaine, all work by increasing the concentration of catecholamines (epinephrine, norepinephrine, and dopamine) in the brain. When these signaling molecules are released from neurons, they activate pathways that have effects such as increasing alertness, sociability, focus, heart rate, and blood pressure.

While all stimulants share this basic mechanism, they vary considerably in the particulars of their activity and the magnitude of their effects. Cocaine and methamphetamine both reach high concentrations in the brain relative to the bloodstream and result in massive surges in dopamine concentration in synapses. These surges are responsible for the euphoria users experience and the addiction and cravings that often follow. Ritalin and Adderall produce a gentler increase in dopamine which does not produce the same high and results in a significantly lower potential for addiction.

Ritalin and Adderall have very similar effects in the body, but there is a slight difference in their mechanism of action. Both medications inhibit transporters that are responsible for the reuptake of dopamine and norepinephrine from the synapse, thus increasing their extracellular concentration. Adderall, however, has the additional effect of increasing the release of dopamine from the neuron, and produces a modestly larger increase in dopamine concentration.

Lisdexamfetamine (Vyvanse) is a recent addition to the stimulant repertoire that promises to be even safer and more resistant to abuse than its predecessors. This compound is pharmacologically inactive until it is metabolized by red blood cells to d-amphetamine (Heal et al., 2013, p. 489). This process occurs in a rate-limited fashion that means the active compound is released slowly and steadily beginning at the time of ingestion, making it virtually impossible to rapidly concentrate it in the brain and thus extremely difficult to abuse.

Non-Stimulant ADHD Meds

Stimulants are definitively first-line in the medical management of ADHD due to their significantly higher efficacy than non-stimulants, which are generally used only in individuals who don’t tolerate stimulants (Zalsman and Shilton, 2016, p. 72). Atomoxetine is the most commonly used non-stimulant and may be of benefit to individuals with ADHD and comorbid anxiety disorders as it has been shown to be therapeutic for both (Kooij et al., 2019, p. 23). Clonidine and guanfacine are rarely used as they produce only modest improvements in symptoms when used in isolation.

ADHD Meds by Age

Although stimulants such as methylphenidate have been FDA approved for children 3-5 years of age, psychosocial interventions are always first line in children under 6 and medications should not be considered in any but the most extreme circumstances (Mattingly et al. 2021, p. 210). While individual responses to medication vary, methylphenidate is observed to be more effective in school-age children while amphetamines appear to produce a better response in college through adulthood (Mattingly et al., 2021, p. 210). Non-stimulants are not considered first-line in any age group.

Extended-release formulations are available for both methylphenidate and amphetamine and are a popular choice in many age groups as they don’t require repeated dosing throughout the day, which can make adherence less difficult in children and adolescents. In adolescents and adults extended-release options also offer the benefit of being less subject to diversion and abuse as large doses are difficult to administer.

Medication

Brand Name

Mechanism

Indications

Possible Side Effects

Amphetamine

Adderall

CNS stimulant

ADHD, narcolepsy, obesity, depression, chronic pain

Insomnia, decreased appetite, nausea

Methylphenidate

Ritalin, Concerta

CNS stimulant

ADHD, narcolepsy, depression

Insomnia, decreased appetite, nausea

Lisdexamfetamine

Vyvanse

CNS stimulant

ADHD, binge-eating disorder

Insomnia, decreased appetite, nausea

Atomoxetine

Strattera

Non-stimulant

ADHD

Abdominal pain, nausea, tiredness, dizziness

Guanfacine

Intuniv, Tenex

Non-stimulant

ADHD, hypertension

Tiredness, dry mouth, constipation, headaches, hypotension

Clonidine

Catapres

Non-stimulant

ADHD, hypertension, drug withdrawal

Dry mouth, dizziness, headaches, hypotension, tiredness

Is ADHD Medication Safe?

There is a substantial volume of data suggesting that stimulants taken as prescribed for ADHD are safe in the short term (i.e. under 2 years) with very few exceptions. Significant adverse events are extremely rare, and the most commonly reported side effects are generally mild to moderate.  However, precaution should always be applied when taking stimulants, as studies by no means rule out 2nd and 3rd order potential negative side effects. Stimulants may cause slight increases in heart rate and blood pressure, but there is currently no evidence to suggest that this increases risk of cardiovascular events (Alpert, 2019).

Precaution should always be applied when taking stimulants, as studies by no means rule out 2nd and 3rd order potential negative side effects

The most common side effects should hardly be considered side effects. Considering that amphetamines have been used to treat narcolepsy since 1935, and that both amphetamine and methylphenidate can be prescribed today to treat hypersomnia, fatigue, and binge eating, it is no surprise that their use is associated with decreased appetite and insomnia. Sleep disturbances are common in untreated ADHD, and often there is no reported decrease in sleep quantity or quality on stimulants.

Depressed appetite may be more problematic as it seems to negatively impact children’s growth in the short term. Growth slowing in the first 6 months of treatment is relatively common, but normalizes in the long term (Zachor et al., 2006, p. 172). There is a strong body of evidence providing reassurance that even with long-term stimulant use there is no statistically significant decrease in adult height.   

Despite persistent concerns over potential for addiction and overdose with prescription stimulants, the evidence suggests that these risks are minimal. While psychological dependence (i.e. feeling reliant on a substance) is certainly possible, there is little evidence for actual physiological addiction, which requires the presence of tolerance and withdrawal. At therapeutic doses, tolerance to these stimulants does not occur, and individuals can remain on the same dose for years with no decrease in effectiveness.

Similarly, apart from a rebound effect consisting of lethargy and increased appetite when the medication is stopped, there appears to be very little risk of true withdrawal even after prolonged use (Krinzinger et al., 2019, p. 963). It is in fact very common for children to only take medications on weekdays or to take a drug holiday over summer breaks with no adverse effects.

Does ADHD Medication Work?

Studies investigating the effect of a single dose of methylphenidate on individuals with ADHD have found marked improvements in neuropsychological functioning in relation to their unmedicated ADHD peers. Methylphenidate has been shown to acutely increase activation and connectivity in regions of the brain involved in planning, attention, and inhibitory control (Berberat et al., 2021, p. 2). A single dose of methylphenidate produces moderate improvements in the ability to stop and start tasks, switch between tasks on demand, and inhibit motor responses. Furthermore, these improvements have been found to correlate with individuals’ self-reported decrease in ADHD symptoms (Vertessen et al., 2022, p. 642).

Comprehensive meta-analyses of the literature provide strong evidence for protective effects of stimulant treatment of ADHD across several categories. Perhaps the strongest body of evidence is for the decreased risk of substance misuse with stimulant treatment. In a study of 40,000 individuals with ADHD followed over 4 years, there was a statistically significant decrease in substance misuse in the treated population vs. the medication-naïve population (Chang et al., 2014, p. 6). Of note, there was a positive correlation between longer duration of stimulant treatment and decreased rate of substance misuse (Chang et al., 2014, p. 6).

Children with ADHD often perform poorly in academic settings relative to their IQ-controlled peers, but meta-analyses have shown an improvement in academic performance with stimulant treatment (Arnold et al., 2020, p. 76). Furthermore, stimulants have been shown to reduce the rates of criminality, mood disorders (depression and bipolar disorder), suicide attempts, traumatic brain injuries, motor vehicle accidents, and fractures (Boland et al., 2020, p. 23). These effects were found not only in comparing treated individuals with untreated individuals, but also in comparing periods when a given individual was adherent or non-adherent to their medication (Boland et al., 2020, p. 23).

While these findings are encouraging, it is important to remember that effect sizes are variable and there are potential confounding factors at play. Individuals with access to treatment and medication may be more likely to come from higher-resource families able to provide additional advantages contributing to favorable outcomes.

Neuroimaging advances have provided us with a window into what may be different in the brains of individuals with ADHD and how stimulants may attenuate those differences. Regions of the brain heavily involved in dopamine signaling (primarily in the basal ganglia and prefrontal cortex) have been found to be smaller in volume in children with ADHD than in healthy controls (Tripp and Wickens, 2009, p. 580). Recent studies indicate that the volumes in these regions normalize with stimulant treatment, ultimately resembling the control population more than the unmedicated ADHD group (Pretus et al., 2017, p, 1239).

How do you Treat ADHD Without Medication?

Stimulant medications are effective treatment options for ADHD, but there are other interventions that should be considered either in place of or in addition to pharmaceuticals. Academic accommodations, increased physical exercise, parental education, limiting sugar / processed food, and good sleep hygiene all benefit children with ADHD and may be sufficient in those with milder presentations. While newer treatment options such as meditation and biofeedback have not yet been proven to be effective, they show some promise for the future. Research has shown that medication has an overall greater effect size than any other intervention when used in isolation, but studies have shown that a combination of behavioral interventions and medication produces the most significant improvement in functioning and reduction in symptomatology (Hinshaw, 2018, p. 307).

The Medicalization of Childhood

It is also patently unethical to medicate children for the convenience of parents and teachers, or at the behest of parents determined to give their child a competitive advantage academically that the child themself likely has no interest in. A critical prerequisite for writing a stimulant prescription for a child must be that it is for their own benefit, not the benefit of their school or family.

The challenge for providers, parents, and teachers is thus to accurately assess to what extent a child is struggling due to ADHD, what adverse outcomes the child is at risk for, and what interventions may mitigate those risks. Given that we often cannot modify their environment, our aim should be to help each individual function their best within the constraints of an environment to which they may be poorly suited, while acknowledging that they are different not defective.

Conclusion

Every medication or drug of abuse has a unique profile of risks and benefits that can vary considerably depending on the individual to whom it is administered; a debilitating adverse effect in one patient could be the primary intended benefit in another. Thus, it is irrational to either demonize a chemical compound or deem it universally safe and effective. To avoid such reductive thinking, we must approach the compendium of information available to us with a balance of skepticism and open-mindedness.

There is strong short-term evidence that stimulants are safe both cardiovascularly and neuropsychiatrically, and a growing body of long-term evidence suggesting the same. However, more longitudinal data is needed to feel confident that stimulant use in childhood does not have adverse effects later in life, particularly as there are still so many unknowns about neurodevelopment.

The evidence does suggest that stimulant use decreases ADHD symptomatology in the short-term and improves long-term outcomes in several key categories. However, the possibility of confounding factors detracts from these findings. There is promising evidence suggesting that stimulants attenuate the structural abnormalities found in the brains of children with ADHD, but these findings are currently more correlative than causative and sometimes lack statistical power.

The current scientific and medical knowledge suggests that psychostimulants are generally safe, and effective at mitigating ADHD symptoms. However, there are still questions and unknowns, and prescribing pharmaceuticals to children should always be preceded by a thorough analysis of risks and benefits. While stimulants may be a useful component of treatment, particularly in severe cases, they should not be administered reflexively to everyone with an ADHD diagnosis.

Ideally, reasonable behavioral, lifestyle, and academic interventions should all be in place before resorting to pharmaceuticals; however, environmental factors often prevent this from being feasible. This is a crucial source of tension surrounding stimulant prescription, and one that must be addressed on an individual basis. Non-pharmaceutical interventions are particularly important in children who meet diagnostic criteria for “mild ADHD” who are likely perfectly healthy and are being saddled with a label that should not apply to them.

Non-pharmaceutical interventions are particularly important in children who meet diagnostic criteria for “mild ADHD” who are likely perfectly healthy and are being saddled with a label that should not apply to them.

We ask elementary school children to sit quietly and focus on school for ten hours per day only to label them disruptive or disabled for failing to do so. Expecting children to behave in ways that are challenging for many adults and subsequently diagnosing them with a disorder when they cannot amounts to the medicalization of childhood.

For children who are further along the normal spectrum of childhood traits including restlessness and distractibility, the gulf between how their brain is expected to work and how it actually functions is even wider. This incompatibility does not mean the brains of children with ADHD are broken or inferior, it simply means they are even less suited to perform in a system unsuited to children’s brains to begin with.

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Anna Witkin

Anna Witkin is a contributing writer for Polygon. Anna holds a BA from UC Berkeley, a Masters in Biomedical Science from Tufts, and researched ADHD and other learning differences during her time at Dartmouth School of Medicine studying for her MD.