Adult ADHD Is Underdiagnosed: Here’s What Pharmacists Need to Know

Attention-deficit/hyperactivity disorder (ADHD) is a chronic neurodevelopmental disorder that persists into adulthood in approximately 2% to 5% of adults worldwide.¹ Although historically conceptualized as a childhood condition, it is now well established that ADHD frequently continues across the lifespan, with symptoms evolving rather than resolving.

Adult ADHD is associated with substantial functional consequences, including impaired occupational performance, financial instability, relationship difficulties, and reduced quality of life. Adults with ADHD also experience significantly higher rates of psychiatric comorbidities, which can complicate diagnosis and management. As a result, adult ADHD is frequently misdiagnosed or masked by coexisting conditions, contributing to delays in appropriate treatment.²

Despite its prevalence and clinical impact, adult ADHD remains underdiagnosed and undertreated, underscoring the importance of accurate recognition, diagnosis, and evidence-based management by clinicians in both primary care and specialty settings.

Recognizing Inattention, Executive Dysfunction, and Impulsivity in Adults

Adult ADHD is characterized by persistent patterns of inattention and/or hyperactivity-impulsivity that interfere with daily functioning. In adulthood, inattention and executive dysfunction—manifesting as poor organization, impaired time management, difficulty initiating and completing tasks, and forgetfulness—are often more prominent than overt hyperactivity, which may present as internal restlessness rather than observable motor activity. Impulsivity may manifest as interrupting others, difficulty waiting, or impulsive decision-making, particularly in occupational, financial, and interpersonal contexts.

Adult ADHD frequently coexists with psychiatric comorbidities, including mood disorders, anxiety disorders, substance use disorders, and personality disorders, which can obscure the underlying diagnosis and contribute to delays in appropriate treatment.³ In addition, physical health conditions may impair cognitive functioning and mimic the executive dysfunction seen in ADHD. Medical conditions that should be considered in the differential diagnosis include sleep disorders, thyroid dysfunction, neurological conditions such as traumatic brain injury and early neurodegenerative disease, and nutritional and metabolic disorders including iron-deficiency anemia, lead toxicity, and vitamin deficiencies.⁴

How Adult ADHD Is Diagnosed: Criteria, Tools, and Clinical Evaluation

The diagnosis of ADHD in adults is clinical and based on a comprehensive assessment rather than a single diagnostic test. Diagnostic criteria require the presence of persistent symptoms of inattention and/or hyperactivity-impulsivity beginning in childhood, typically before age 12, that continue to cause clinically significant functional impairment in adulthood across 2 or more settings, such as work, school, or home. Because symptom expression often changes over time, adults may report fewer overt hyperactive behaviors and more prominent inattention and executive dysfunction, necessitating careful longitudinal history-taking.

The most widely used screening tool for adult ADHD is the Adult ADHD Self-Report Scale (ASRS-v1.1), developed by the World Health Organization, and includes the 6-item screener (ASRS-6) and the full 18-item version (ASRS-18).⁵ The ASRS-6 is commonly used in primary care settings for initial screening, whereas the ASRS-18 allows for more detailed symptom assessment and monitoring. More recently, the ASRS-5 was developed to align with the Diagnostic and Statistical Manual of Mental Disorders Fifth Edition criteria, incorporating updated language that better reflects adult symptom expression.⁶ Although these instruments support identification, they do not replace a structured clinical evaluation. A thorough diagnostic workup should also assess for psychiatric comorbidities and medical conditions that may mimic or mask ADHD to ensure accurate diagnosis and appropriate management.

First-Line Treatments for Adult ADHD: Stimulants and Behavioral Therapy

Treatment of adult ADHD involves a multimodal approach, with pharmacotherapy as first-line treatment supplemented by psychotherapy, including cognitive-behavioral therapy, and patient education. Stimulant medications are considered first-line pharmacologic agents due to their rapid onset of action and superior efficacy. These include methylphenidate-based formulations and amphetamines such as lisdexamfetamine (Vyvanse; Takeda) and mixed amphetamine salts. Stimulants exert their effects by blocking the reuptake of dopamine and norepinephrine, increasing their availability in the prefrontal cortex.⁷

In adults, amphetamine formulations including mixed amphetamine salts extended-release and lisdexamfetamine are often preferred in the absence of contraindications, as they demonstrate greater efficacy than methylphenidate (Relexxii; Vertical Pharmaceuticals LLC) in many patients.⁸ These medications significantly improve core symptoms such as attention, task initiation, and impulse control, resulting in improved functioning across occupational, academic, and interpersonal domains.

Amphetamine stimulants are available in immediate-release formulations lasting up to 6 hours and extended-release preparations providing symptom control for up to 12 hours. Selection is guided by patient preference, cost, and availability. Common adverse effects include dry mouth, insomnia, irritability, dysphoria, reduced appetite, weight loss, and headache. Stimulants may exacerbate tic disorders and cause dose-dependent increases in heart rate and blood pressure, necessitating routine cardiovascular monitoring. As Schedule II controlled substances, stimulant medications carry a high potential for misuse and dependence.

Medical contraindications include uncontrolled hypertension, significant structural heart disease, symptomatic cardiovascular disease, and untreated hyperthyroidism. Neuropsychiatric contraindications include active substance use disorders, bipolar 1 disorder, florid psychosis, Tourette disorder, and severe tic disorders.⁹

Titration and Monitoring

Stimulant treatment should begin at a low dose and be titrated at intervals of approximately 7 days based on clinical response and tolerability. During titration, patients should be monitored every 1 to 2 weeks using validated rating scales such as the Conners’ Adult ADHD Rating Scales or the Barkley Deficits in Executive Functioning Scale.¹¹ Tolerability assessments should include appetite, sleep, mood, anxiety, weight, blood pressure, and heart rate. Once stabilized, follow-up visits may occur every 3 months initially and at least annually thereafter. Long-term monitoring should also assess for the development of tolerance, which may be managed through dose adjustment, medication class changes, or supervised drug holidays.⁸

Non-Stimulants and Off-Label Drugs

Atomoxetine (Stattera; Eli Lilly and Co) and viloxazine (Qelbree; Supernus Pharmaceuticals) are the primary FDA-approved nonstimulant treatments for adult ADHD. These agents are preferred in patients with a history of substance use, stimulant contraindications, or poor stimulant tolerability. They are not controlled substances and provide continuous symptom coverage, although clinical efficacy is generally lower than stimulants and onset of benefit may take 4 to 6 weeks. Common early adverse effects include nausea, headache, and insomnia. Atomoxetine is associated with sexual dysfunction and requires blood pressure monitoring. Both agents carry boxed warnings regarding suicidal ideation in younger populations.¹²

Additional off-label options include extended-release guanfacine (Intuniv; Shire US Inc) and clonidine (Kapvay; Shionogi Pharma, Inc), which are less effective and commonly associated with sedation and hypotension. Bupropion (Wellbutrin; Bausch Health) is frequently used off label in patients with comorbid depression or substance use disorders.¹²

Access Issues in the United States

Significant barriers to ADHD treatment persist in the United States due to medication shortages, inconsistent pharmacy availability, and limited access to specialized care. Immediate-release stimulant formulations, particularly generic amphetamine/dextroamphetamine, are the most affected. Contributing factors include Drug Enforcement Administration manufacturing quotas, consolidation among generic manufacturers, and increased demand associated with expanded telehealth-based ADHD diagnoses.¹³

Pharmacy stock outages frequently require patients to contact multiple locations or travel long distances, disrupting treatment continuity. Partial prescription fulfillment and forced medication substitutions further complicate management and may compromise clinical stability.¹⁴

Improving Outcomes Through Early Diagnosis and Tailored Care

Adult ADHD is a complex neurodevelopmental disorder with significant functional and psychosocial consequences. Optimal outcomes depend on accurate diagnosis, careful differentiation from medical and psychiatric mimics, and individualized treatment strategies that balance the high efficacy of stimulant medications with safety considerations and alternative therapies. Addressing systemic challenges, including medication shortages, misuse risk, and inequities in access to care is essential. Integrating pharmacologic treatment with behavioral interventions and reducing structural barriers to care can substantially improve long-term outcomes and quality of life for adults with ADHD.

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