Is it ADHD—or something else? The importance of careful assessment for the proper diagnosis and effective treatment of the third most common mental health disorder worldwide.
The prevalence of attention-deficit/hyperactivity disorder (ADHD) in the worldwide pediatric population has been stable over the past 30 years except in the United States, where cases have increased.1 According to a 2016 parent survey, approximately 6.1 million US children (9.4%) had received a diagnosis of ADHD.2 Worldwide, ADHD is the third most common mental health disorder, following depression and anxiety.3 Overall, girls (5.6%) are less likely to be diagnosed with ADHD than boys (12.9%).2
A 2021 global systematic review and meta-analysis suggested that the prevalence of persistent adult ADHD was 2.58% and the prevalence of symptomatic adult ADHD was 6.76%, with 139.84 million and 366.33 million affected adults worldwide in 2020, respectively.4 ADHD appears to impact men more than women. In adults, ADHD appears to decrease as an individual ages.4
Etiology is still not clearly understood; however, combinations of genetic, neurological, and environmental factors likely contribute to its pathogenesis and symptom expression.3 Genetic factors are implicated, but the mechanism of action is not completely clear. Family, twin, and adoption studies have strongly suggested that ADHD is highly inheritable. Moreover, genetic studies have documented the gene sets interfering with neurotransmitter pathways in the brain that implicate rare copy number variants or the collection of higher deletions, as well as the duplications impacting gene transcriptions that are more likely to be found in individuals with ADHD.3,5-7
Pre-, peri-, and postnatal environmental factors play a significant role in the development of ADHD. Some evidence suggests prenatal factors include the mother’s lifestyle during pregnancy.8 For example, prenatal alcohol exposure can lead to hyperactive, disruptive, and impulsive behaviors and increase the risk of psychiatric disorders.9,10 Maternal smoking during the prenatal developmental period has been linked to increased risk of ADHD11 and hyperactivity.12 Perinatal factors, such as very low birthweight, can result in a 2-fold increase in the likelihood of ADHD.13
ADHD is conceptualized as a disorder of childhood that gradually diminishes over the lifespan.8 However, several prospective longitudinal studies have challenged the prevailing assumption that childhood ADHD and adult ADHD affect the same individuals, and that they share the same neurodevelopmental vulnerabilities.14-16 The results of these studies suggest that more than two-thirds of individuals with adult ADHD never had childhood ADHD. Adult ADHD had been generally neglected in epidemiological studies, until recently, as researchers attempt to estimate the true prevalence of ADHD in adults. Furthermore, researchers are exploring whether ADHD is solely a neurodevelopmental disorder that presents in childhood, or whether ADHD can be acquired during other developmental periods. The prevalence of persistent adult ADHD from childhood and that of symptomatic adult ADHD were 2.58% and 6.76% in 2020, respectively.17
The diagnostic assessment of ADHD can be complicated, as inattention, impulsivity, and difficulties with concentration can be driven by myriad factors. It is well documented that children and adolescents diagnosed with ADHD often have 1 or more cooccurring disorders18 (Table 119).
According to a study by Elia and colleagues, oppositional defiance disorder was the most common comorbid disorder at 41%, followed by depression/dysthymia at 22% and general anxiety disorder at 15%.19
Approximately 60% to 100% of children with ADHD have 1 or more comorbid disorders that persist into adulthood. Autism spectrum disorder, with a comorbid rate of 42%, and learning disorders (math, reading, and spelling), account for 10% and 92% of comorbidities. Tourette syndrome accounts for 55% comorbidity. Children with ADHD experience major depression at a rate higher than children without ADHD (12% to 50%). Regarding anxiety symptoms, children with ADHD have a prevalence rate between 15% and 35%.20
In adults with ADHD, the most common cooccurring psychiatric disorders are bipolar disorder, depression, anxiety disorders, substance use disorders (SUDs), and personality disorders.21 ADHD has a high cooccurring prevalence with bipolar disorder: Estimates range between 9.5% and 21.2%, with bipolar I disorder being more likely.22 ADHD and depression commonly cooccur at even higher rates, ranging from 18.6% to 53.3%.23 Individuals with ADHD are also at higher risk for developing anxiety disorders than the general population, with rates approaching 50%.24-26 SUDs are likely the most common cooccurring condition with ADHD—specifically, alcohol and/or nicotine, cannabis, and cocaine use.27
Research support for the intersection of ADHD and personality disorders is scant compared with the support of other psychiatric cooccurring conditions. However, reports indicate that personality pathology is present in approximately 50% of adults with ADHD—most commonly cluster B and C personality structures—and up to 25% of adults with ADHD have 2 or more personality conditions.28
Diagnosing ADHD can be a complicated process. It is imperative to obtain historical information such as academic performance records and previous psychological testing reports, if ever tested.
There are several significant barriers to diagnosis and treatment in ADHD, including overlapping symptomology between ADHD and mood and anxiety disorders, SUDs, learning disabilities, information processing disorders, auditory processing disorders, and psychosocial factors. It is important to note that some individuals overcome ADHD-related deficits by developing and mastering compensating skills. This also can impact the accuracy of ADHD diagnosis.
Evidenced-based assessment includes multi-informant/multimethod procedures and validated measures. This approach should be guided by current research and include test data to support clinical observations and, ultimately, an accurate ADHD diagnosis. Table 2 highlights several measures used in ADHD assessments.
Treatment considerations should be informed by functional outcomes including symptom reduction, increased quality of life, and improved daily, academic, and occupational functioning.29 Efficiency at working or studying, maintaining stable relationships, containing or curbing impulsivity, and being satisfied with life overall are indicators of improved functioning. Moreover, adherence to treatment is key to successful management of ADHD.
First-line treatments for ADHD are pharmacologic: stimulants and nonstimulants. Stimulant medications include methylphenidate, mixed amphetamine salts, and lisdexamfetamine dimesylate. Nonstimulants used in ADHD treatment include atomoxetine and alpha-2-adrenergic agonists. Table 3 highlights several ADHD medication options, although the effectiveness of psychopharmacological treatments is beyond the scope of this paper.
For children and adolescents, a well-established body of evidence supports the effectiveness of psychosocial treatments, including behavioral management interventions (eg, parent training, classroom interventions, peer-based interventions), training interventions (eg, cognitive training, neurofeedback, organization), cognitive behavioral therapy (CBT), and physiological treatments (eg, play and other physical activities).30-33 CBT, the preferred nonpharmacological treatment for adult ADHD, consistently reduces its core behavioral symptoms.34
Usually first diagnosed in childhood and sometimes persisting into adulthood, ADHD has extensive implications for academic achievement, relationships, finances, and employment. In addition, untreated ADHD carries greater risk of accidental injuries and substance abuse. Thus, careful assessment is of utmost importance to properly diagnose and then treat the disorder.
Dr Blassingame is an assistant professor and licensed clinical psychologist at Harris Health System in the Menninger Department of Psychiatry and Behavioral Sciences at Baylor College of Medicine in Houston, Texas. Dr Buitrago is a psychology fellow at Baylor College of Medicine.
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