The first 3 KASs are related to the evaluation and diagnosis of ADHD. As noted, ADHD is the most common neurodevelopmental disorder. Pediatricians and other PCCs should play a key role in the evaluation and diagnosis of ADHD [8,9]. The process requires establishment of a sustained relationship with child and family. The child with a history of ADHD risks (e.g., extremely low birth weight, family history of ADHD) should be monitored in a primary care setting. Many parents bring their child to the primary care clinic with concerns about ADHD. Concerns may also be identified during routine screening at preventive visits. Additionally, parents may visit the clinic at the recommendation of a teacher or other caregiver. In these situations, the pediatrician or PCC should initiate an evaluation for ADHD.

A diagnosis of ADHD should be made based on DSM-5 criteria, including documentation of symptoms and impairment in more than one major setting. The clinician should identify the chief concerns and history of symptoms, and the family, medical, and psychosocial history should be reviewed. Relevant information may also be obtained from the diagnostic interview, school and other reports, and academic records. DSM-5–based rating scales could be helpful for collecting information. There are minimal changes in ADHD behaviors from the prior DSM publication (DSM-4); thus, other DSM-based rating scales can be used.

In the evaluation for ADHD, comorbid conditions should be screened for. A wide range of emotional or behavioral conditions, developmental conditions, and physical conditions can be comorbid with ADHD [10-17]. These conditions may affect the treatment for ADHD and also mimic ADHD symptoms. Detailed history-taking and a review of systems are required, which might reveal other disorders or problems (e.g., sleep problems, developmental delay, or trauma history). Hearing and visual problems also need to be screened for, and internalized symptoms, such as anxiety and depression, may be noticed during the interview with the child or adolescent. Information from the child’s school might reveal comorbid or mimicking conditions, such as depression and anxiety, disruptive behavior disorders, or learning disabilities. Recording clinical observations and conducting a physical examination are important as the patient may present with language disorders, developmental disorders, or other physical conditions such as genetic syndromes.

The fourth, fifth, and sixth KASs are related to the treatment of ADHD. ADHD is a chronic condition, such as asthma, and affected individuals have special health care needs (Fig. 2). The AAP suggested the principles of the chronic care model and the medical home for such chronic conditions (Fig.3) [18-20]. ADHD should be managed according to the same principles. This model may be beneficial, especially for parents with ADHD or those with a low socioeconomic status. Further, it may be helpful in maintaining ADHD treatment. It is important to establish a team approach involving the child and their family, school personnel, and mental health clinicians.

For children aged 4 to 5 years, parent training in behavior management (PTBM) and/or behavioral classroom interventions is recommended as a first-line ADHD treatment [21,22]. Weekly courses are designed to help parents learn age-appropriate developmental expectations, behaviors that strengthen the parent-child relationship, and specific management skills for problem behaviors. One example of evidence-based PTBM is parent-child interaction therapy, a dyadic therapy for parents and children. PTBM is a group or individual program on a weekly basis. The programs offer specific techniques in behavior management. PTBM is applicable even without a definite ADHD diagnosis and can help parents to learn age-appropriate development. Subsequently, it may inform the diagnostic evaluation for ADHD. Thus, PTBM is also recommended if an ADHD diagnosis is doubtful. Moreover, training intervention has recently emerged as an ADHD treatment modality, targeting specific deficient behaviors and skills. In this context, extensive training, practice, and coaching are provided. Overall, a combination of PTBM and training interventions may be most effective. PTBM and training interventions can also be applied to address behavior problems that do not fully meet the DSM-5 criteria.

Methylphenidate can be considered for children aged 4 to 5 years in the following cases: (1) moderate-to-severe ADHD that did not respond to behavioral interventions and (2) in areas in which evidence-based behavioral treatments are not available. However, the clinician needs to assess the benefits and harms of starting such medication. Only methylphenidate has sufficient evidence regarding its use in this age group [2,22]. However, it should also be noted that the evidence does not yet meet the approval level for the U.S. Food and Drug Administration (FDA). Other stimulant or nonstimulant medications have also not been adequately studied [23]; thus, they are not recommended for use in preschool-aged children.

For children aged six to 11 years, the guideline suggests the use of FDA-approved medications for ADHD, together with PTBMand/or behavioral classroom intervention (preferably both). An FDA-approved stimulant (methylphenidate or amphetamine) is the first choice in medication treatment [24]. These 2 stimulant medications have similar benefits and adverse effects; however, only methylphenidate is currently available in Korea. Meanwhile, FDA-approved nonstimulant medications include norepinephrine reuptake inhibitors (atomoxetine) and selective α-2 adrenergic agonists (e.g., guanfacine or clonidine) [25-28]. Nonstimulant medications have also demonstrated sufficient, albeit less robust, efficacy (i.e., the ratio of stimulants:nonstimulants effect size to control is 1.0:0.7) [29]. Behavioral treatment in combination with medication has positive effects [30,31]. This combined treatment approach is beneficial, especially for children with comorbid anxiety or living in low socioeconomic environments. The effects of behavioral therapies tend to persist, but the effects of medication cease when administration stops. Moreover, behavioral therapy allows for a lower medication dosage to be prescribed [32]. In school-aged children, school programming (educational intervention and/or accommodation) and supports are necessary parts of the treatment plan [20]. The clinician needs to collaborate with the child’s school to enhance supports and services.

For adolescents aged 12 to 18 years, FDA-approved medications, behavioral/training interventions, and educational interventions/supports are also recommended. In adolescents, a special concern should be taken to provide long-term medication coverage. Long-acting or supplemental short-acting medications can be helpful. Long-acting or additional short-acting medications can be helpful. The clinician needs to communicate bidirectionally with the adolescent patient. Transition to adult care should also be prepared.

Lastly, in its ADHD treatment guidelines, the AAP recommends that the clinician should titrate doses of ADHD medications to reach their maximum benefit with tolerable side effects. The Multimodal Treatment of Attention-deficit Hyperactivity Disorder (MTA) study demonstrated that, when the full range of methylphenidate was administered, ADHD symptoms improved in more than 70% of study participants [31]. Stimulants can be effectively titrated on a weekly basis; in urgent cases, this may be completed within a three-day period. Follow-up visits are recommended monthly until the optimal response plan is developed, then every 3 months thereafter within the first year. Subsequent visits are suggested at least twice a year. After several years, the medication can be tapered. A patient who does not respond to stimulants may still respond to nonstimulant medications. Atomoxetine elicits a maximal response approximately 4 to 6 weeks after initiation, while guanfacine and clonidine demonstrate maximal effects about 2 to 4 weeks after; however, only guanfacine and clonidine have been approved as adjunctive therapy to stimulants by the FDA [33]. Other combinations may be used on an off-label basis. The frequent adverse effects associated with stimulants include headache, stomachache, weight loss, and sleep disturbance. Uncommon and serious side effects of stimulants at high doses include hallucinations and other psychotic symptoms. The MTA study showed that height growth diminished in the range of 1 to 2 cm and was not compensated for after [31]. Increases in heart rate (HR) and blood pressure (BP) were clinically insignificant and mild [34]. The risk of sudden cardiac death was not increased [35-39]. Nevertheless, the clinician should monitor both the patient's HR and BP along with their height and weight. Before initiating therapy with stimulant medications, it is important to obtain the patient's history of cardiac symptoms and a family history of sudden cardiac death and cardiovascular symptoms. If these risk factors are present, the clinician should consider further evaluation. The frequent adverse effects of atomoxetine include somnolence, abdominal pain, and weight loss [40-42]. Height growth delays may existin the first one to 2 years but are compensated for after [43]. Increased suicidal thoughts have infrequently been found, and this black box warning should be noted. For guanfacine and clonidine, the adverse effects include somnolence, dry mouth, abdominal pain, dizziness, headache, bradycardia, and hypotension [8,44,45]. Because of rebound hypertension,these medications should be tapered off [46].

KAS 7 is related to comorbid conditions in patients with ADHD and was newly added in the 2019 ADHD guideline. The AAP highlights that the primary pediatrician needs to take responsibility for mild-to-moderate ADHD, anxiety, depression, and substance use. The accompanying PoCA suggests several validated scales for comorbid conditions. ADHD rating scales also include items for screening for comorbidities. AAP mental health initiatives provide the algorithm for broader mental health. KAS 7 is integrated with this algorithm. The primary pediatrician may not be trained or experienced enough to manage ADHD with comorbid conditions. Patients with complex ADHD with severe comorbidities should be referred to a specialist. Those with urgent conditions, such as suicidal attempt, self-injury, and temper outbursts, need to be transferred immediately. The primary pediatrician should still be prepared and participate as a team member in these situations.