What is ADHD: A Complete Guide to Understanding ADHD in 2025

Written By Matthew Miceli

ADHD affects an estimated 404 million adults globally and 16.13 million adults in the United States alone as of April 2025. This common neurodevelopmental disorder impacts daily functioning through patterns of inattention, hyperactivity, and impulsivity. Despite growing awareness, challenges in adult diagnosis persist, with notable gender and ethnic disparities. This guide explores the current understanding of ADHD, including its neurological basis, diagnostic criteria, treatment approaches, and real-life impacts.

As a practicing psychologist with over 8 years of experience specializing in ADHD assessment and treatment, I've helped countless individuals discover whether they have ADHD and develop effective strategies for managing their symptoms. My passion lies in working with people who are unsure if they have ADHD and guiding them toward life-changing breakthroughs.

What is ADHD: Definition and Classification

So what is ADHD? Attention-deficit/hyperactivity disorder is a medical condition affecting brain development and activity. It specifically impacts attention, self-control, and behavioral regulation. Major medical organizations, including the American Psychiatric Association, recognize ADHD as a chronic condition that can significantly affect functioning across multiple life domains.

Contrary to outdated beliefs, ADHD isn't simply a behavioral problem or the result of poor parenting. Modern research shows it's a complex neurodevelopmental condition with genetic components and environmental influences that affect the development and functioning of specific brain regions. At Verdant Psychology, we understand the importance of recognizing ADHD as a legitimate medical condition requiring proper assessment and support.

The Evolution of ADHD Understanding: Insights from APA

Our understanding of ADHD has changed dramatically over time. Historically, ADHD was seen primarily as a childhood condition that children would eventually "grow out of." Early research focused mainly on white boys, which led to significant underdiagnosis in females and certain ethnic groups.

This historical bias continues to influence current diagnostic practices and tools, which often don't adequately address adult and female presentations of ADHD.

In recent decades, there's been growing recognition that ADHD frequently persists into adulthood. In 2013, the DSM-5 revised diagnostic criteria to better account for adult presentations, reducing the required symptoms for diagnosis in adults and increasing the age of onset from 7 to 12 years.

In my clinical practice, I've seen firsthand how these evolving understandings have impacted patients. Many adults come to me saying, "I've always felt different, but no one ever considered ADHD because I wasn't hyperactive or disruptive as a child." These individuals often experience profound relief when they finally receive an accurate diagnosis that explains struggles they've faced throughout their lives.

Types and Core Symptoms of ADHD According to Mayo Clinic

ADHD appears in three distinct types, each characterized by different predominant symptom patterns according to the Mayo Clinic:

Combined features is the most common presentation found at Verdant Psychology. To get a full diagnosis, reach out today by booking a consultation here.

Predominantly Inattentive Presentation

People with this type primarily struggle with attention-related symptoms including:

  • Difficulty sustaining attention on tasks or activities

  • Frequent careless mistakes in schoolwork, work, or other activities

  • Trouble following through on instructions and failing to finish duties

  • Difficulty organizing tasks and activities

  • Avoiding tasks requiring sustained mental effort

  • Frequently losing items necessary for tasks or activities

  • Being easily distracted by extraneous stimuli

  • Being forgetful in daily activities

This presentation is more common in girls and may be harder to identify as symptoms are less externally visible than hyperactive behaviors. The inattentive type may be more likely to persist into adulthood.

Predominantly Hyperactive-Impulsive Presentation

This type is characterized by symptoms of excessive activity and impulsivity:

  • Fidgeting or squirming when seated

  • Leaving seat when remaining seated is expected

  • Running or climbing excessively in inappropriate situations (or feelings of restlessness in teens and adults)

  • Difficulty engaging in quiet leisure activities

  • Being "on the go" or acting as if "driven by a motor"

  • Talking excessively

  • Blurting out answers before questions are completed

  • Difficulty waiting one's turn

  • Interrupting or intruding on others

This presentation is more commonly identified in boys due to the disruptive nature of these symptoms.

Combined Presentation

The combined type includes a mixture of both inattentive and hyperactive-impulsive symptoms. This is the most common presentation of ADHD and represents individuals who meet criteria for both symptom clusters.

Prevalence and Demographics

Global and U.S. Prevalence

As of 2025, an estimated 404 million adults have ADHD globally, according to extrapolations from 2020 research conducted by the Journal of Global Health. In the United States, approximately 16.13 million adults have ADHD. 

Gender Differences

ADHD has historically been diagnosed more frequently in males than females, with a ratio that has varied between studies but typically shows a male predominance. However, this disparity is now understood to reflect differences in symptom presentation rather than actual prevalence differences:

  • Boys tend to exhibit more hyperactive and impulsive behaviors, which are more noticeable and disruptive, leading to higher referral rates

  • Girls more commonly present with inattentive symptoms, which are less outwardly disruptive and may go unrecognized

This difference in presentation has contributed to significant underdiagnosis in females, as traditional diagnostic criteria and clinical attention have focused on the more visible hyperactive-impulsive symptoms.

Diagnosis Considerations

Diagnosing ADHD involves a comprehensive assessment process, as no single test can definitively identify the condition. The diagnostic evaluation typically includes:

Diagnostic Criteria

For a diagnosis of ADHD, symptoms must:

  • Be present before age 12

  • Occur in two or more settings (such as home, school, work)

  • Interfere with functioning or development

  • Not be better explained by another mental disorder

For children, at least six symptoms from either the inattention group or the hyperactivity-impulsivity group must be present. For adolescents age 17 and older and adults, at least five symptoms are required.

If you're considering whether you or a loved one might have ADHD, professional ADHD testing is crucial for an accurate diagnosis and appropriate treatment planning.

Diagnostic Challenges

Several factors complicate the diagnostic process:

  • Symptoms can overlap with other conditions

  • Adult ADHD may present differently than childhood ADHD, with decreased hyperactivity but ongoing struggles with impulsiveness, restlessness, and attention

  • Historical views of ADHD as a childhood condition have created barriers to adult diagnosis

  • Diagnostic tools and criteria have traditionally been developed based on male presentations, leading to underdiagnosis in females

Causes and Risk Factors

The exact cause of ADHD remains unknown, but research points to a complex interplay of factors:

Genetic Factors

ADHD has a strong genetic component, with heritability estimates ranging from 60-80%, making it one of the most heritable psychiatric conditions.

Neurobiological Factors

Brain imaging studies have identified differences in brain structure, function, and connectivity in individuals with ADHD, particularly in areas involved in attention, impulse control, and executive functions.

Environmental Risk Factors

Several environmental factors may increase ADHD risk:

  • Exposure to environmental toxins (such as lead) during pregnancy or early childhood

  • Maternal use of alcohol or tobacco during pregnancy

  • Premature birth or low birth weight

  • Brain injuries or traumas

It's important to note that ADHD can sometimes be confused with or co-occur alongside other conditions. If you're interested in understanding how ADHD relates to or differs from conditions like autism, our guide on signs of autism in adults may be helpful.

Impact on Daily Life and Functioning

ADHD affects multiple domains of life, with impacts varying across development:

Academic and Professional Impact

ADHD can significantly affect educational and career outcomes:

  • Children with ADHD often struggle with classroom behavior, assignment completion, and academic achievement

  • Adults with ADHD experience higher rates of unemployment and underemployment

  • Workplace challenges include disorganization, missed deadlines, difficulty prioritizing tasks, and problems with time management

Social and Relationship Functioning

ADHD can strain interpersonal relationships:

  • Impulsive behaviors and poor emotional regulation may lead to social difficulties

  • Maintaining friendships and romantic relationships can be challenging

  • Adults with undiagnosed ADHD experience greater disruptions in family, work, and social lives than those who have received a diagnosis

Emotional Well-being

ADHD is associated with various emotional challenges:

  • Poor self-esteem and increased self-criticism

  • Sensitivity to criticism

  • Higher rates of anxiety and depression

  • Emotional dysregulation

Daily Functioning Challenges

Among individuals with ADHD, several key challenges in daily functioning have been identified:

These firsthand accounts highlight the practical, day-to-day struggles that often aren't captured in clinical descriptions but significantly impact quality of life.

In my 8+ years working with ADHD patients, I've observed that these everyday challenges often cause the most distress. One patient described it perfectly: "It's not the big things that break me down—it's the constant small failures and the shame that comes with them." Helping patients develop personalized strategies to address these specific pain points is where I've seen the most meaningful breakthroughs in their quality of life.

Treatment Approaches

ADHD is highly treatable, with most individuals experiencing significant symptom improvement with appropriate interventions.

Medication

Pharmacological treatments are among the most effective interventions for ADHD:

  • Stimulant medications (such as methylphenidate and amphetamine derivatives) are first-line treatments

  • Non-stimulant medications (such as atomoxetine, guanfacine, and clonidine) are also effective for some individuals

  • Medication use for ADHD increased substantially during the COVID-19 pandemic, particularly among women, possibly due to reduced barriers to care through telehealth expansion

Behavioral Therapy

Various behavioral approaches help manage ADHD symptoms:

  • Cognitive-behavioral therapy

  • Parent training for families of children with ADHD

  • Organizational skills training

  • Social skills training

  • Educational accommodations and interventions

Multimodal Treatment

Research indicates that a combination of medication and behavioral therapy often yields the best results for most individuals with ADHD. Treatment plans should be personalized based on age, symptom presentation, comorbid conditions, and individual preferences.

In my practice, I've found that treatment is rarely one-size-fits-all. For some patients, medication provides the foundation they need to implement behavioral strategies effectively. For others, targeted therapy addressing specific executive function challenges makes the biggest difference. What's most rewarding is helping patients who've struggled silently for years discover strategies that allow them to thrive. One adult patient told me, "For the first time in my life, I feel like I'm driving my own car instead of being a passenger watching myself make mistakes."

ADHD Across the Lifespan

Childhood ADHD

ADHD symptoms typically first emerge in early childhood:

  • Often first identified in school-aged children (ages 3-6) when classroom disruptions or academic difficulties arise

  • Hyperactive symptoms may be more prominent in children

  • Can significantly impact educational achievement and social development

Adolescent ADHD

As children with ADHD enter adolescence:

  • Hyperactive symptoms may become less obvious but still present as internal restlessness

  • Academic demands increase, potentially exacerbating attention difficulties

  • Risk-taking behaviors may increase due to impulsivity combined with typical adolescent development

  • Social challenges may become more pronounced

Adult ADHD

ADHD often persists into adulthood, though symptom presentation may evolve:

  • Hyperactivity typically decreases but is replaced by feelings of restlessness

  • Attention difficulties and impulsivity often continue

  • Executive function challenges (planning, organization, time management) frequently become more problematic as adult responsibilities increase

  • Adults may develop compensatory strategies but still struggle in various life domains

Current Challenges and Future Directions

Diagnostic Improvements

There is a critical need to improve ADHD diagnostic practices:

  • Developing more sensitive tools for identifying ADHD in underdiagnosed populations, particularly women and ethnic minorities

  • Creating more accessible screening methods to overcome healthcare access barriers

  • The American Professional Society of ADHD and Related Disorders announced plans to develop the first U.S. guidelines for diagnosing ADHD in adults, addressing a "critical need for healthcare providers, patients, and the public"

Telehealth and Digital Interventions

The COVID-19 pandemic accelerated the adoption of telehealth for ADHD assessment and treatment:

  • Telehealth expansion reduced barriers to care, potentially contributing to increased diagnosis and treatment rates among adults

  • Digital screening tools and interventions show promise for improving access to ADHD services

Wrapping Up

ADHD is a complex neurodevelopmental disorder affecting millions of children and adults worldwide. Our understanding has evolved significantly, moving from viewing it as a childhood behavioral issue to recognizing it as a lifelong neurodevelopmental condition with biological roots.

Despite increased awareness and improved diagnostic practices, significant challenges remain, especially regarding the underdiagnosis of ADHD in women, adults, and certain ethnic groups.

Effective treatment combining medication and behavioral strategies can effectively manage ADHD symptoms and improve quality of life, but access to these interventions remains uneven. Future directions should focus on improving diagnostic tools, expanding treatment access, and better understanding ADHD across diverse populations and life stages.

After more than a decade specializing in ADHD assessment and treatment, I've witnessed countless breakthroughs as patients finally understand the neurobiological basis of challenges they've faced throughout their lives. The most rewarding part of my work is helping people who've always wondered "what's wrong with me?" discover that their brains are simply wired differently—not better or worse—and then equipping them with strategies to harness their unique strengths while managing their challenges.

If you believe you or a loved one may be experiencing symptoms of ADHD, Verdant Psychology offers comprehensive ADHD testing and evaluation services to help you get the answers and support you need. My passion is helping people who are unsure if they have ADHD find clarity and develop personalized strategies for success.

By addressing these challenges and seeking appropriate professional guidance, we can better support the millions of individuals affected by ADHD and help them reach their full potential.

Additional Resources

For more information about ADHD, consider exploring these authoritative sources:

Matthew Miceli
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