The Evolution of ADHD: Examining the Last 25 Years — and the Future

In the arc of science, 25 years isn’t a long time. Yet, in the realm of attention deficit hyperactivity disorder (ADHD), the last quarter century has been pivotal, yielding myriad advances in our understanding of the condition. Thanks to ongoing research on diagnosis and treatment, we know more about the causes of ADHD, its trajectory, how it presents across different groups, and the treatments that work — plus those that don’t. We’ve learned a great deal about ADHD against a backdrop of increasing societal awareness of mental health.

As important as it is to recognize how far we’ve come, it’s crucial to acknowledge the long road ahead. Psychology, after all, is a relatively young science, and there is still so much we have to discover and improve upon — from dismantling stigma to creating equitable access to care for all.

Evolving ADHD: How Our Understanding Has Changed

While some aspects of ADHD haven’t changed significantly in the last 25 years — like the symptom groupings of inattention and hyperactivity/impulsivity outlined in various versions of the DSM — following are a few notable changes in the ways we diagnose and understand ADHD today.¹

From “Subtypes” to “Presentations”

In 1994, the DSM-IV designated three subtypes of ADHD — inattentive, hyperactive/impulsive, and combined. Over time, however, research proved the subtypes unreliable across development. That is, an individual who was diagnosed with the combined subtype as a child could go on to exhibit relatively more inattentive symptoms in adolescence or adulthood, to the point that they no longer meet criteria for the combined subtype. In recognition that ADHD symptoms may present differently across time, subtypes became “presentations” in the DSM-5, released in 2013.

The notion of a mental health condition presenting differently across individuals and across time is not new. The symptoms of depression, for example, have hundreds of different combinations, and we still call it depression. The 2013 update made room for this variability in ADHD.

[ADD Test: Could You Have Inattentive ADHD?]

Chronic Symptoms and Remission Rates

The last 25 years of research tell us that ADHD tends to be chronic; the majority of kids and teens diagnosed with ADHD will still meet clinical criteria for the condition in adulthood. Today, it’s generally accepted that ADHD doesn’t just “go away.”² There is some evidence that hyperactive/impulsive symptoms do remit or lessen to some degree over development. Inattentive symptoms largely persist into adulthood and may continue to cause impairment in a variety of ways, from work settings to relationships.

While researchers are still learning how ADHD might present and impact individuals in adulthood, both from a strength-based and impairment approach, more studies are needed on ADHD across the lifespan. ADHD in older adults, for example, isn’t well understood.

Comorbidities Are the Rule, Not the Exception

ADHD, we now know for sure, rarely presents in isolation — mood disorders, anxiety, learning differences, and substance use disorders are commonly comorbid with the condition.³ Shared underlying genetic and brain-based systems could explain the connection, but living with ADHD itself can also cause certain comorbidities to develop.

Consider that ADHD symptoms remain highly stigmatized; perceptions abound that children with ADHD simply aren’t trying hard enough and need to be disciplined. When a child with ADHD is on the receiving end of this kind of negative feedback from parents and other adults, they could go on to demonstrate oppositional, defiant, and/or argumentative behaviors toward adults — partly because they have come to believe authority figures aren’t on their side.

[Read: What Is Complex ADHD? Symptoms, Diagnosis & Treatment]

ADHD is also highly linked to peer rejection, academic difficulties, and a host of other negative developmental outcomes that could increase one’s risk for a depressive episode or anxiety about one’s abilities.¹ So, although individuals with ADHD may be biologically predisposed to comorbid diagnoses, environmental factors can facilitate their development as well.

Increasingly Complex Understanding of ADHD’s Etiology and Outcomes

Our understanding of risk factors for ADHD, including developmental and environmental factors, along with the developmental sequelae of ADHD, has evolved considerably.

Genetic, Environmental, and Epigenetic Research

We’ve seen huge advances in our understanding of gene influences on ADHD and other mental health disorders, and the way that environmental factors might exert large effect sizes on the presentation of symptoms. Advancements in epigenetics, the field of research that examines how the environment changes gene expression over time, has helped us move away from the idea of a single cluster of genes that determines ADHD.

There are, in fact, many, many genes that could play a role in the risk profile for ADHD — and those genes are perhaps also shared with many other mental health conditions. One thing is certain from this research: As science evolves, it suggests that the answers we seek — regarding whether there are objective markers of ADHD or genes that define it — are likely quite complex.

ADHD Outcomes

Evidence shows that ADHD, especially if untreated, affects multiple domains of life; individuals with ADHD are more likely to be in traffic accidents, to experience peer difficulties and tumultuous interpersonal relationships, and to drop out of school, be expelled from school, and experience academic failure earlier.³ The latter is particularly troubling when we consider that ADHD has historically been underrecognized and undertreated in marginalized and disadvantaged communities; academic difficulties and expulsions can start the school-to-prison pipeline, which disproportionately impacts Black youth.⁴ Individuals may end up incarcerated before ever learning that they have ADHD and that it was the root cause of their difficulties in school and early life.

Spotlight: Compelling ADHD Research Today

New Diagnostic Constructs

Researchers are working to capture certain presentations possibly in the form of modifiers or subtypes of ADHD. Cognitive disengagement syndrome (CDS), characterized by excessive mind-wandering, mental confusion, and slowed behaviors, has been proposed as a potential modifier for the ADHD diagnosis or a subtype. (CDS was previously referred to as sluggish cognitive tempo).⁵ Whether difficulties with emotional regulation as well as sleep difficulties represent subtypes or modifiers of ADHD are other topics of research.

The Search for Objective Markers of ADHD Symptoms

Diagnosing clinicians think of “FIDI” — frequency, intensity, duration, and impairment — when considering if a patient’s symptoms point to ADHD or, frankly, any other mental health condition. ADHD diagnoses today are still largely based on behavioral symptoms and, to some degree, the clinician’s subjective impressions of a patient’s experience. (That’s assuming the clinician completes a thorough, quality diagnostic interview.)

The question is: Are there better markers that can help us objectively diagnose ADHD? Could there be, say, task-based markers or biological markers that would allow us to index risk for ADHD or at least combine the results with a diagnostic interview to tell us, with high confidence, if a patient has ADHD? These questions have characterized the last few decades of ADHD research, and while there’s hope that we might reach an additive model at some point, the science is not there yet.

ADHD and Sex Differences

We’ve learned a lot about sex differences in ADHD and how symptoms potentially present differently across males and females. It’s commonly thought that females may be more likely to present with the inattentive cluster of symptoms and less likely to present with hyperactive-impulsive symptoms. At the same time — because of stigma, stereotypes related to gender role presentations, and clinician bias — when females do present with ADHD symptoms, those symptoms may be incorrectly or wholly attributed to anxiety or depression. Researchers are also studying whether ADHD in females has a different time of onset and severity.

Neuroscience of ADHD

Functional magnetic resonance imaging (FMRI) has emerged as a tool to identify brain areas, circuitry, or networks that might be implicated in ADHD. Some core research findings have stood the test of time: Frontal structures and networks of the brain appear to be underutilized/under-activated in ADHD. At the same time, the default mode network (DMN) — brain networks that are meant to be active when an individual is not focused on a task — has been found to be overactive in individuals with ADHD, and likely interferes when focus is required.⁶

A look at the field of neuroscience shows how open science has become in the last 25 years. Institutions are sharing their data sets to make for larger combined study data sets — valuable for testing and replicating findings of earlier research. There are also ongoing multiple large-scale national and multinational studies dedicated to understanding brain science as it relates to ADHD and various other mental health conditions.

ADHD Treatment: How Evidence Is Expanding to Fill Gaps

ADHD Treatment Then

In 1998, the evidence base for ADHD treatment was around medication, behavioral parent and school interventions, and combined multimodal treatment.⁷ Stimulant medication was known to be effective in addressing ADHD symptoms in children, particularly during school hours, by increasing focus and enabling students to complete academic tasks. It was also understood that coaching parents and teachers on certain behavioral skills could help them manage their child’s/student’s ADHD symptoms through the course of the day, even during “hot zones” (e.g., mornings, homework time, bedtime). Medication and behavioral treatment together were considered more effective than either one alone.

Treatment challenges and gaps identified at the time included the following:⁷

• The prevalence of non-evidence-based treatments being applied to ADHD. Take play therapy, for which there was no evidence that skills learned in the therapist’s office transferred to the outside world. This was true in 1998, and it’s true today. (This is not to say that there is no benefit to play-based interventions, only that there is no evidence that it helps ADHD.) The evidence base was also thin for applying standard individual cognitive behavioral interventions to target ADHD symptoms.
• The short-term effects of interventions. Be it medication or behavioral interventions, questions abounded about the sustained effectiveness of an ADHD treatment, especially once an intervention was removed.
• The symptom improvement ceiling. In terms of behavior, many interventions for ADHD at the time only brought children within one standard deviation of the typical range for children of their age.

ADHD Treatment in the Present

When developing evidence-based treatment practices, 25 years is a short span of time. From examining a potential intervention in a few cases to executing randomized research trials and replicating results, it takes considerable time and resources to show that a treatment works. Still, there have been important advances in ADHD treatment in the last quarter century.

How the ADHD Treatment Evidence Base Has Expanded⁸

• More focus on the factors affecting the success of established treatments: A key question researchers are asking today: Does addressing caregivers’ mental health concerns improve ADHD treatment outcomes for their children?
• Proven effectiveness of behavioral peer interventions and organizational skills training: Today, strong evidence shows that these interventions improve these common areas of impairment in children with ADHD.
• Greater understanding of sequencing of psychosocial and psychiatric interventions: It’s well established that medication and behavioral interventions together make for greater treatment outcomes. That said, if choosing to sequence, evidence indicates that starting with psychosocial treatment (parent training/school training) might produce better outcomes than starting on medication first.
• Interest in incorporating adolescent-specific techniques, like motivational interviewing and collaborative problem-solving, to better engage these individuals in treatment.
• Efforts to ensure diverse populations are represented in ADHD treatment research, though much more work is needed in this area.

Smoke But No Fire: ADHD Interventions with Weak Strength of Evidence

A handful of interventions have sprung up over the years, and some have gained popularity for their purported impact on ADHD symptoms. The reality is that, judging by studies, there is only weak evidence that the following interventions are effective enough to merit consideration as established evidence-based practices for ADHD.⁸

• Cognitive training — computer-based programs that encourage a child to practice certain skills in hopes of boosting executive functions — doesn’t seem to work for ADHD, though some encouraging findings show that adults can help mediate the transfer of these skills to real life.
• There is hope that at some point, research will indicate more clearly how and whether neurofeedback might be effective for ADHD. However, at this point, there is neither a standardized understanding of how neurofeedback can be applied nor evidence that it truly generalizes to real-world skills.
• Physical activity and taking omega-3 supplements can certainly form part of a healthy lifestyle, but studies do not indicate that these interventions specifically have a significant impact on ADHD symptoms.

Challenges — and Hopes — for the Future of ADHD

Ongoing challenges in the field of ADHD are as follows:

• ADHD is highly stigmatized. To this day, the validity of the diagnosis is still debated, and it’s still commonly called an excuse for laziness and lack of effort.
• Psychiatric interventions are also heavily scrutinized and stigmatized. Despite decades of research on treatments for ADHD, and the fact that ADHD medications are some of the most well-studied of any psychiatric medication class, there is still a lot of trepidation surrounding them. A shortage of child and adolescent psychiatrists and an incredible wealth of media narratives about the “evils” of psychiatry fuel stigma.
• Mental health parity and access to care remain grave concerns. Access to care is even more difficult for historically marginalized and/or underserved populations, as well as individuals of lower socioeconomic status.
• Psychosocial treatments require significant investment. Whether it’s behavioral parent training or organizational skills training, these treatments, while effective, are high-effort and usually require ongoing maintenance — a tough ask for patients and families.
• Use of unproven treatments sets the field and individuals back in many ways. When families and patients pursue interventions that claim to help ADHD, only to find that such interventions are ineffective, the result could discourage these individuals from seeking help and from thinking that they can be helped. At worst, it increases mental health stigma and leads to the development of comorbid mental health concerns.
• Negative life experiences tied to ADHD may decrease one’s ability and willingness to seek help. Individuals with ADHD (especially undiagnosed) are vulnerable to peer rejection, academic failure, and other unfortunate outcomes that can cut off avenues for help.

But across the board, the future of ADHD looks bright. There is much to be excited and hopeful for.

ADHD Science and Treatment Continue to Advance

Evolving tools and science will help us further understand ADHD and ultimately allow us to go beyond today’s largely behavior-based approach to diagnosing the condition. There is good reason to believe that the future of ADHD holds precision medicine — the ability to better delineate risk factors for the condition and a tailored course of treatment for individuals.

A major priority is expanding the mental health workforce and recruiting diverse and representative clinicians to meet patient treatment needs. The field is also envisioning novel ways to reach patients, such as capitalizing on telehealth. In the larger scheme of treatment, we see interest in the development of intensive interventions — treatments that are shorter in term but just as effective in reducing symptoms and impairment.

Societal Awareness of ADHD and Turning Tides

Yes, ADHD is stigmatized. But awareness and acceptance have undoubtedly improved over the last 25 years, and efforts are ongoing to fight stigma and build equity in mental health care. The changing ways we talk about mental health are evidence of these efforts; we’re opting for “neurodivergence” and other non-stigmatizing terms to capture individual differences and the inherent diversity of human brain function. For the future of ADHD, perhaps the greatest hope of all comes from the growing societal belief that mental health care is a fundamental human right.

ADHD Then and Now: Next Steps

• Read: Reflections on the Dark Ages of ADHD Misconceptions
• Read: The 15 Most Corrosive ADHD Myths
• Watch: Unlocking the Future of ADHD: Advances in Research, Diagnosis, & Treatment

The content for this article was derived from the ADDitude ADHD Experts webinar titled, “ADHD Then and Now: How Our Understanding Has Evolved” [Video Replay & Podcast #447] with Dave Anderson, Ph.D., which was broadcast on March 21, 2023. This article is part of our “25 Years of ADDitude” collection, which reflects on the past, present, and future of ADHD and ADDitude since the publication’s founding in 1998.

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