#88. Benefits, Null Effects, and Harmful Effects of ADHD Medications

Stimulants to treat ADHD apparently do not improve learning and can have serious harmful side effects.

Aug 09, 2025

Dear friends,

By MissLunaRose12 /CC /Wikimedia Commons..

In Letter #87 I presented evidence that ADHD, though called a “disorder,” is better thought of as a personality characteristic, which can vary from person to person in degree and, for most, is problematic or not depending on the environmental context. For many if not most children diagnosed with ADHD, the primary problem is adjustment to the demands of forced schooling. Most diagnoses originate because of behavioral problems in school, where demands are made that run counter to the nature of childhood.

Rates of diagnosis increase when schooling is made more rigid; and many people find that their ADHD problems diminish or even vanish when they leave conventional schooling for home schooling or graduate and go on to a life where they can choose activities more compatible with their interests and personality. Research (described in Letter #87) shows that most people diagnosed with ADHD are good at focusing on tasks that interest them, but are easily distracted from boring tasks, the kinds of tasks that predominate in school. Admittedly, this is not true for all people diagnosed with ADHD.

For a small percentage the trait is so strong that it is a problem no matter the context, and for them drug therapy may be in order regardless of the risks. But, I contend, we are crazy to believe that conformity to our increasingly toxic school system is so important that we are willing to drug huge numbers of our nation’s children, especially boys, primarily to conform to it. As I pointed out in Letter #87, 23% of American boys have been diagnosed with ADHD by or before age 17, and most of that group are taking or have taken strong, brain-altering drugs primarily so they can adapt to the strictures of school.

Now, in this letter, I summarize research findings concerning effects of the drugs used to treat ADHD. Currently two drugs are most common. One is a mix of d-amphetamine and l-amphetamine, sold most often under the brand name Adderall. The other is methylphenidate, sold most often under the brand name Ritalin. These drugs act in similar ways on the brain, promoting the release of the neurotransmitters dopamine and norepinephrine and inhibiting their reuptake into neural endings. The drugs are referred to as stimulants, because one of their effects is to promote alertness. When amphetamines are used recreationally, or abused, they are commonly called “speed,” because of their energizing effect, and they can be addictive. For good reasons, it is illegal to use amphetamines or methylphenidate without a prescription.

In what follows, I describe some of the effects of these drugs that researchers have documented to date. I begin with the behavioral effects for which they are prescribe and then move on to short- and long-term harmful effects.

The drugs immediately reduce ADHD symptoms but may not do so in the long term.

The reason these drugs are so popular is because, in many cases, though not all, they quickly reduce the symptoms that led to a diagnosis of ADHD. Countless studies have shown that, on average, kids treated with stimulants after a diagnosis of ADHD become more organized, focused, and compliant, especially in school, than they were before. This is what led many researchers early on to consider amphetamines and methylphenidate to be wonder drugs for ADHD. This finding should perhaps not be surprising. One of the reasons people have long used and abused speed is because it helps them focus on tasks that are otherwise uninteresting.

Subsequent longitudinal research, however, took some of the shine off that wonder. The most systematic large long-term study to date is the Multimodal Treatment Study of Children with ADHD (MTA). For this, a group of more than 500 children diagnosed with ADHD were randomly assigned to different treatment conditions for a period of 14 months and then were assessed periodically for a period of 16 years. At first, the drugs seemed to have remarkably positive effects. Those getting the drugs were doing better on all behavioral measures pertaining to ADHD symptoms than those not getting a drug. However, by the 3-year follow-up, and again at the 8-year follow-up, there were no discernable behavioral differences among the groups (Jensen et al., 2007; Molina et al, 2009. There was no difference based on the 14-month initial treatment condition, nor was there any difference based on the degree to which they had continued or not continued taking the drugs after that initial period. In the 8-year follow-up assessments, those in the different treatment groups were indistinguishable from one another by every measure—including “grades in school, arrests, psychiatric hospitalizations, and other clinically relevant outcomes.”

Overall, all groups improved in behavior over time following the first assessment after the drug regimen began, but those not taking a drug improved more, wiping out the early advantage produced by the drug. It is not clear if this loss of effect was because the drug effects diminished with continued use or because natural maturity, as the kids grew older, resulted in diminished need for the drugs. The researchers concluded that the only discernable long-term effect of the drugs in their study was on height of the participants. Those regularly on a drug were about one inch shorter on average than those in the no-drug condition. At the 16-year follow-up, when they were young adults, those in the initial drug treatment groups were still on average an inch shorter than the others (Swanson et al, 2017).

In a recent interview with New York Times writer Paul Tough (here), James Swanson, the lead researcher who initiated the long-term MTA study, reported sadly that the only thing the study proved for sure about effects of stimulants for ADHD over time is that they suppress growth. He expressed regret about his initial enthusiasm for the drugs and the effect such enthusiasm may have had in overselling them.

The drugs improve classroom behavior but apparently do not improve learning.

The main purpose of school, presumably, is for children to learn academic material. The initial assumption of those prescribing drugs for ADHD, and certainly of parents who agreed to the drugging of their children, was that the drug would not only promote more organized, compliant, less disruptive classroom behavior but, in doing that, would lead to more learning. To date, however, there appears to be no good evidence supporting this assumption and considerable evidence against it. Drug treated kids are more likely to attend to and complete their seat work and homework, but test scores do not increase beyond those of untreated kids. Several controlled studies have attempted to show that the drugs improve learning in ADHD kids and have failed. In such studies the kids on drugs look like they are learning more because they were more focused in class, and in in some cases the kids themselves believe they are learning more, but test scores reveal no improvement in knowledge or skills compared to the control condition of ADHD kids not on drugs. Here, briefly, are two such experiments.

Leanne Tamm and her colleagues (2017) identified a sample of 216 children in grades 2-5 who had been diagnosed with ADHD and were also significantly behind their classmates in reading and randomly sorted them into three treatment conditions: medication alone; extra reading instruction alone; and both medication and extra instruction. The children were subsequently assessed for improvement in their ADHD symptoms (as rated by teachers and parents) and for improvement in reading. The results were that medication alone reduced their ADHD symptoms but did not improve reading; reading instruction alone improved their reading but not their ADHD symptoms; and the combined treatment improved both, but it did not improve reading more than did instruction alone. Stated differently, for ADHD-diagnosed children who were given extra training in reading, the drug treatment improved classroom behavior but did not improve the effectiveness of the lessons. The unmedicated kids learned as much, on average, from the reading lessons as did the medicated kids, even though by all appearance they paid less attention to the lessons.

William Pelham and his colleagues (2022) conducted a conceptually similar experiment with 173 children, ages 7 to 12, in a therapeutic summer camp. Each camper participated in two three-week-long sets of classes in science, social studies, and vocabulary. In a balanced design, some were medicated for the first three-week session and not the second, and some were medicated for the second session but not the first. The result was that, based on test scores, the children learned just as much of the content of each course when not medicated as they did when medicated. Again, medication may have improved attention to the material as it was taught, but it did not improve encoding or retention.

It seems paradoxical that medicated ADHD kids who seem to be working harder and paying more attention in class, when tested, exhibit no more learning than unmedicated ADHD kids who are more disorganized. A possible resolution of the paradox derives from an experiment in which non-ADHD adults were asked to solve complex problems after taking a dose of methylphenidate, d-amphetamine, modafinil (all of which are used to treat ADHD) or a placebo (Bowman et al, 2023). The result was no average difference among the conditions in number of problems solved, but an analysis of the moves they made in solving the problems, and the time they took to solve them, showed that those in the placebo condition were more efficient in finding solutions. They made more initial correct choices, thereby exhibiting better logic, and solved the problems in less time. The researchers concluded that the drugs increased effort and persistence but reduced efficiency in solving the problems. If the same is true for ADHD kids, then the drugs might increase the effort kids put into studying but reduce the efficiency of that effort. Perhaps increased effort compensates for reduced efficiency, resulting in no overall difference in test scores.

The drugs used to treat ADHD are sometimes called “smart drugs,” but research such as that just described suggests that they increase motivation and sustained effort but may decrease, not increase, cognitive ability. It might be more appropriate to call them “dumb drugs.” Other research has revealed that college students who are not diagnosed with ADHD often take Adderall or Ritalin (illegally) as a means of enabling them to put in long hours of effort required to write a term paper or study for an exam (Vrecko, 2013). In interviews they report that, with the drugs, they find such tasks to be interesting, even exciting, and can fully immerse themselves in them. Without the drugs, they find the tasks boring, burdensome, and are easily distracted. Whether or not one has ADHD, the drugs seem to have the effect of enabling one to focus intently, with interest, on work that would otherwise seem boring and aversive.

The drugs can have a multitude of short-term and long-term harmful effects.

For some kids, stimulants have intolerable side effects, no matter which drug and no matter the dose (within a clinically effective range). My ADHD-diagnosed stepson was one of them. He said the drugs made him feel hollow and humorless, not at all himself, and I have read and heard reports from others who rejected the drugs for such reasons. Many find that the drugs reduce their appetite and result in unhealthy degrees of weight loss. In fact, in the 1950s and ‘60s, before the ADHD era, amphetamines were widely prescribed for weight loss. For many, the drugs produce insomnia, which is no surprise given that they are stimulants. Moreover, amphetamines can be addictive, and some who have taken Adderall for periods of weeks or more experience withdrawal symptoms when they discontinue it. All these effects vary, for unknown reasons, from person to person. For some they are intolerable, for others they may be just annoyances.

A large recent study conducted at McLean Hospital in Massachusetts revealed that Adderall (amphetamines), but not Ritalin (methylphenidate), markedly increased the odds of having episodes of psychosis or mania in ADHD-diagnosed patients (Moran et al, 2024). The effect was dose-dependent; those on a high dose (>30 mg) were more than five times as likely to experience such episodes as those on no drug or on Ritalin. This finding is especially troublesome, given the recent trend in the U.S. toward increased use of Adderall and decreased use of Ritalin, especially for adults (Moran et al., 2024).

Another recent study, this one in South Korea, revealed that methylphenidate (Ritalin) increased the incidence of depression, by about 50%, for ADHD-diagnosed children (Oh et al., 2022). The depression subsided if the treatment was discontinued. The researchers did not assess amphetamines (Adderall) for this effect, perhaps because amphetamines are rarely prescribed for children in South Korea.

The effects I’ve listed so far are short-term, which can be reversed by discontinuing the drug. Potentially more concerning are long-term effects, which show up only after prolonged drug use. I already mentioned one such effect, reduction in growth if given during childhood. A more debilitating possible effect, for which there is increased evidence, is Parkinson’s Disease.

Parkinson’s is a brain disease that rarely appears before age 60 and more often appears after age 70. It is characterized at first by tremors and tics and then, over time, by larger uncontrolled movements and loss of ability to move in a coordinated way, as well as a constellation of other symptoms. It is caused by degeneration of dopamine-using neurons in an area of the brain called the basal ganglia—the same neurons on which amphetamines and methylphenidate act to reduce the symptoms of ADHD.

Experiments with laboratory animals have long shown that amphetamines and methylphenidate are toxic to dopaminergic neurons in the basal ganglia; they damage and even destroy large numbers of those neurons (Baumeister, 2017). In one study, for example, squirrel monkeys that had been treated with amphetamines for four weeks—at a dose designed to create plasma concentrations comparable to that for drug treatment in humans—were found to sustain neural degeneration in the basal ganglia, which did not recover over time (Ricaurte et al., 2005).

Because Parkinson’s usually only appears in old age, and because the great majority of people treated with stimulants for ADHD have not yet reached that age, data are still scarce concerning the effect of these drugs on Parkinson’s in humans. However, a large study in Utah found that patients between the ages of 21 and 49 who had been treated for ADHD over long periods with stimulants were nearly four times as likely to have developed a disease of the basal ganglia similar to Parkinson’s (but not as extreme) as were ADHD patients who had not been medicated (Curtin et al., 2018). Other studies have likewise shown an increased rate of movement disorders, presumably representing damage to the basal ganglia, in adults after long-term treatment with amphetamines or methylphenidate (Nam, 2022). Such studies have led to predictions that, as the early cohorts treated with ADHD drugs age, we will see increased incidences of Parkinson’s Disease, especially among men (because boys and men have received the drugs much more often than girls and women).

Concluding Thoughts

So, where are we? On the plus side, stimulants used to treat ADHD result in more orderly, focused, less disruptive behavior, which is especially valuable for adapting to school requirements and, for some, can be valuable for adapting to many other contexts as well. On the negative side, although they increase focus in studying and solving problems, evidence suggests that they decrease cognitive efficiency, resulting, on average, in no net increase in learning or problem-solving success. Moreover, for some, the drugs have short-term negative effects, which fortunately are reversible if one stops using the drugs. These include (for some) suppression of spontaneity and humor, loss of appetite, insomnia, depression and, more rarely, episodic psychosis or mania.

A well-established long-term effect of the drugs, when taken in childhood, is reduction in height, which may or may not be regarded as negative. (Though I’m compelled to add that any drug that reduces growth must be having a variety of potentially negative physiological effects, some of which have yet to be discovered.) Finally, the drugs are known to destroy certain neurons in the brain and, through that means, cause brain-based movement disorders in some who have used the drugs over a long period, and there is reason to believe that, as early users of the drugs age, we will find that they increase the rate of Parkinson’s Disease.

For some people, at the extreme of ADHD symptoms, the benefit of the drugs outweighs the risks, but those are a relatively small percentage of the huge numbers of people, including small children, who are being prescribed the drugs today. Any physician or psychiatrist prescribing such drugs, and any parent considering such drugs for a child, or any teacher recommending such drugs, or any child or adult who might begin taking such drugs, should understand and consider seriously the risks. Drug companies don’t get rich by telling you about the risks of their drugs (which are in small letters or spoken very rapidly); they get rich by exaggerating the benefit. Not all medical authorities who prescribe the drugs are adequately aware of the risks, as they get much of their information from the drug companies. If school is the main reason for starting your kid on a stimulant, I strongly recommend that you consider some alternative to conventional public school, such as homeschooling, which may be a far better fit for your child’s personality (see here).

And now, what do you think? If you have had experiences with ADHD, with or without medication, feel free to share them in the comments section below. This Substack is, in part, a forum for discussion. Your thoughts and questions are valued and treated respectfully by me and other readers, regardless of the degree to which we agree or disagree. Readers’ thoughtful comments and questions add to the value of these letters for everyone.

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