Attention-Deficit/Hyperactivity Disorder in Adults

Adult attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder of executive function associated with inattention, disorganization, and/or hyperactive/impulsive behaviors occurring in people 17 years or older.¹ Adult ADHD is a continuance of childhood symptoms, with 29% of cases persisting into adulthood.^2–4 Although some studies have suggested that a late-onset ADHD subtype can occur that is not a continuance from childhood, more data are needed, and this theory is not considered in the current diagnostic criteria.^5,6 Adults with ADHD are at higher risk of unemployment, educational underachievement, financial difficulties, substance misuse, criminality, divorce, motor vehicle crashes, workplace accidents, and overall mortality compared with the general population.^2,7,8

Research suggests that there is a genetic component to ADHD. Family, twin, and adoption studies have shown a heritability rate of 74%.⁹ More recently, ADHD has been linked with dozens of genetic mutations that do not cause ADHD in isolation, but as mutations increase so does risk of ADHD, disease severity, and manifestation of comorbid conditions with genetic overlap (e.g., depression, autism).¹⁰ This polygenicity is driving the development of polygenic risk scoring methods that would help with early disease identification.¹¹

In 2006, an estimated 4.4% of U.S. adults had ADHD.¹² The prevalence has increased to at least 14.6% based on 2022 data and affects adults across demographics.¹³ The increasing prevalence of adult ADHD may be due to a true increase or to an increase in diagnosis as more patients and clinicians become knowledgeable about the disorder. When ADHD was first described in 1902, it was believed to affect only children. The persistence of ADHD into adulthood was not recognized until the early 1990s.⁸ In 2013, the Diagnostic and Statistical Manual of Mental Disorders, 5th ed., (DSM-5) relaxed diagnostic criteria from symptom onset before 7 years of age to before 12 years. Diagnostic criteria for ADHD did not substantially change with the 2022 release of the DSM-5 text revision (DSM-5-TR).¹

Differential Diagnosis

To diagnose adult ADHD, clinicians must rule out other medical and psychiatric conditions that could account for the patient’s symptoms. Emotional dysregulation is common in ADHD, but there is substantial overlap with symptoms of other mental disorders. Because other mental disorders commonly co-occur with ADHD, it is important to screen patients for multiple mental health issues (Table 1). The DSM-5-TR Self Rated Level 1 Cross-Cutting Symptom Measure—Adult is a 23-item measure that assesses for signs of depression, anxiety/stress, mania, somatization, self-harm, psychosis, sleep issues, memory issues, personality disorders, and substance misuse.¹ Other conditions that may have symptom overlap with ADHD include prior traumatic brain injury, thyroid dysfunction, medication adverse effects, organizational skill deficits, environmental factors, and malingering.^1,8,12,14

Diagnostic Recommendations

For suspected cases of ADHD, a three-part approach to the assessment is recommended. First, the assessment findings can be considered negative if the patient reports no symptoms before 12 years of age,¹ although patients may not recall or have insight into symptoms before that age. Second, validated self-report and observer screening measures for ADHD symptoms can be completed and interpreted as positive or negative. One example is the Adult ADHD Self-Report Scale.^15–17 Third, the DSM-5-TR diagnostic criteria require the presence of several inattentive or hyperactive-impulsive symptoms in two or more settings that have a major impact on function.¹ Clinicians should be aware that some people with ADHD may appear high performing in one setting but spend a significant amount of time and effort maintaining that level of performance or have reduced performance in other settings. Also, many patients lack insight into their condition and are unable to wholly communicate their symptomatology.^15,18

If a patient’s presentation and screening results are suggestive of ADHD, they must then meet DSM-5-TR criteria for a formal diagnosis (Table 2).¹ There are several validated self-report diagnostic tools that have been derived from DSM-5-TR criteria^{8,16,17,19,20} (Table 3).

To avoid an inappropriate diagnosis of ADHD, collection of corroborating collateral information (e.g., childhood medical records, work evaluations, school transcripts, observer reports) is strongly recommended.^8,14 Free, research-supported observer forms include the Current Behaviour Scale – Partner Report and the retrospective Childhood Behaviour Scale – Parent Report.¹⁴

If a patient’s evaluation findings are consistent with ADHD, the diagnosis is further classified by presentation type, disease severity, and remission status.¹ ADHD’s presentation type and severity can change over time, and patients can go into remission. In the absence of a clear ADHD diagnosis, the patient may be referred to cognitive behavior therapy for distress regarding cognition or to brief psychoeducational counseling for concentration concerns.

Diagnostic Recommendations

Clarifying which symptoms are most distressing to the patient at the time of evaluation is important because there are often comorbid psychiatric concerns. Common psychiatric comorbidities, substantial symptom overlap with other disorders, and potential malingering complicate adult ADHD diagnosis. Diagnostic self-report tests tend to lack specificity and result in a high false-positive rate if used alone.^21–27 Given ADHD’s high heritability and persistence from childhood, however, a family history of ADHD in a first-degree relative or personal history of a childhood ADHD diagnosis greatly increases the likelihood of ADHD in an adult.^2–4,9 A comprehensive combination of a clinical evaluation, screening, diagnostic testing, and collateral information is often sufficient to make an accurate diagnosis in these cases.

In patients without a first-degree relative with ADHD or personal history of a childhood ADHD diagnosis, particularly if corroborating collateral information is lacking or confounding comorbid mental illness is suspected, neuropsychological diagnostic testing should be considered. Neuropsychological testing, which is performed by or under supervision of a licensed neuropsychologist or psychologist, incorporates symptom validity testing and performance measures (e.g., working memory, sustained attention, task omissions, commission errors, reaction time, response time variability) and can assist with diagnosis when combined with self-report and collateral information.^22,28–32 The financial burden of this testing to the patient should be a consideration. Medicare/Medicaid reimbursement rates for neuropsychological testing costs are $75 to $150 per hour. The process involves hours of testing and interpretation of results, and the overall cost of evaluation can reach thousands of dollars.^33,34

Although pharmacologic regimens are the first-line treatment for adult ADHD, psychotherapy is an option to avoid medication. Many types of therapy can help, but symptoms often improve with cognitive behavior therapy. There is also evidence that mindfulness and cognitive remediation are effective interventions for core symptoms. There is weaker evidence for the use of group dialectical behavior therapy and hypnotherapy due to the small sample sizes, lack of suitable control conditions, and a high risk of bias.³⁵ In many cases, cognitive behavior therapy for ADHD in adults addresses psychoeducation and adaptive coping skills, and involves the patient’s partner or family members.³⁶

Table 4 summarizes pharmacotherapy options for ADHD in adults.

Stimulant Medications

Stimulants are a first-line therapy for adult ADHD given the robust data supporting their effectiveness. Stimulants include permutations of amphetamine and methylphenidate. Although there are multiple formulations, a systematic review concluded that most adults with ADHD have a favorable response to stimulants, with some studies indicating a preference for amphetamines over methylphenidate.³⁷ Approximately 70% of adults with ADHD have immediate improvement in attentiveness and reduced distractibility, with moderate to large effect sizes. Effects are seen within 1 hour of administrating immediate-release or controlled-release formulations. Controlled-release formulations, which remain effective for 6 to 10 hours, may improve compliance because they require only once-daily dosing.³⁸

Potential adverse effects of stimulants include insomnia, headaches, elevated blood pressure, elevated heart rate, decreased appetite, weight loss, dry mouth, anxiety, and depression. Because of their potential to persistently increase blood pressure or heart rate, stimulants are contraindicated in those with uncontrolled hypertension, angina, a history of myocardial infarction, arrhythmias, significant heart valve disease, or cardiomyopathy. Before initiating stimulant therapy, electrocardiography may be recommended for some patients, based on their symptoms, conditions, and personal or family cardiovascular history. Stimulants are also contraindicated in those who are pregnant or have a history of tics, drug addiction, alcohol misuse, severe anorexia, or psychosis.^8,14,39

Stimulant Misuse and Diversion

Stimulant medications are classified as Schedule II substances by the U.S. Drug Enforcement Administration due to the high potential for abuse. They increase levels of dopamine in the brain, which has rewarding effects.⁴⁰ In 2021, more than 3.4 million people 18 years and older in the United States misused prescription stimulants, most commonly amphetamines.⁴¹ An estimated 66% of people who misuse prescription stimulants get the medications from family or friends with prescriptions, and 20% obtain prescriptions themselves by presenting to clinicians with exaggerated or fabricated symptoms.⁴² In adolescents and college students, nonmedical stimulant use may be as prevalent as medical use.⁴³

The risk of abuse is increased among persons with a history of substance use disorder.⁴⁰ Controlled-release formulations are harder to inject or snort than immediate-release formulations and thus are less likely to be abused. Prescription stimulants are most often abused to achieve intoxication, lose weight, self-treat mental illness, or improve cognition and productivity.^41,43 About 5% of people without ADHD who use stimulants for nonmedical purposes will increase their use, leading to substance use disorder and dependence.⁴⁴ Rates of overdose deaths from noncocaine stimulants have been exponentially increasing in the United States since 2012, with more than 32,500 deaths in 2021.⁴⁵ To prevent misuse of prescribed stimulants, controlled substance agreements and monitoring methods such as random urine drug screening, patient reevaluation at least every 3 months, and local prescription drug monitoring programs may be used.⁴⁶

Nonstimulant Medications

For those who do not respond to stimulants, have major adverse effects with stimulant use, or have a contraindication to stimulant use, nonstimulant medications approved by the U.S. Food and Drug Administration (FDA) for adult ADHD are atomoxetine and viloxazine (Qelbree), which are selective norepinephrine reuptake inhibitors.³⁷ One of the benefits of using nonstimulant medications for ADHD treatment in adults is a lower risk of abuse compared with stimulants.⁴⁷ They may also be beneficial for patients with concomitant anxiety. Although nonstimulants generally take longer than stimulants to reach full effect (about 4 weeks), some patients see improvement in ADHD symptoms in as early as one week.⁴⁸

For those who do not respond to stimulant treatment or FDA-approved nonstimulant options, off-label medications may be considered. Bupropion can be used for those with comorbid conditions such as depression, anxiety, and smoking. Clonidine and guanfacine (Intuniv), alpha-2 and alpha-2a adrenergic receptor agonists, respectively, are approved only for use in children and adolescents, but they have been used in adults despite limited evidence.^37,49 Similarly, the evidence is limited for tricyclic antidepressants, and they are not approved for ADHD at any age.³⁸

In adults with a new ADHD diagnosis, at least monthly follow-up is appropriate until the patient has adequate functional improvement.¹⁹ During these visits, it is important to address treatment expectations, medication adverse effects, vital signs (particularly blood pressure and heart rate in patients taking stimulants), medication effectiveness, and the need for dosing adjustments. Drug holidays during weekends and vacations are sometimes recommended, but the evidence is lacking.¹⁴

Many of the diagnostic tools in Table 3 can also be used to reassess patients for condition improvement while they are undergoing treatment optimization.^{8,14,19,20,50} If an individual becomes dependent on stimulants, rapid cessation may lead to withdrawal symptoms, including fatigue, uncontrolled body movements, irritability, and confused thoughts, which may take weeks to resolve. To reduce this risk, a taper is recommended to wean patients off high doses of stimulants.⁵¹

This article updates previous articles on this topic by Post and Kurlansik,⁵⁰ and Searight, et al.⁵²

Data Sources: Essential Evidence Plus, PubMed, MEDLINE, Cochrane database, American Academy of Family Physicians, UpToDate, and Centers for Disease Control and Prevention were searched using an extensive list of synonyms for ADHD treatment, diagnosis, and testing. Search dates: May 2023 to January 2024, and July 2024.

The opinions and assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the U.S. Air Force, the U.S. Department of Defense, or the U.S. government.