Attention-deficit/hyperactivity disorder (ADHD) is characterized by persistent patterns of inattention, hyperactivity, and impulsivity, typically manifesting during childhood and often persisting into adulthood. Globally, the prevalence of childhood ADHD is estimated at approximately 5%, with rates similar to those reported in South Korea [1,2]. ADHD symptoms frequently continue into adulthood, with approximately 60% of individuals diagnosed as children still experiencing symptoms similar to adults [3].

Many studies have suggested that impulsivity and hyperactivity symptoms in individuals with ADHD tend to diminish with age, whereas inattention symptoms are relatively persistent [4]. One of the hallmark features of adult ADHD. Deficits in attention make it difficult for individuals with ADHD to sustain their focus on tasks, and they are more easily distracted in situations requiring concentration, making it difficult to complete everyday tasks [5].

These symptoms significantly impair social, academic, and occupational functioning during adulthood. Academic underachievement is a major challenge faced by adults with ADHD. Adults with ADHD are less likely to pursue higher education compared to the general population, with attention-related ADHD symptoms contributing to lower performance in reading, spelling, and mathematics [6]. Secondly, workplace challenges are common, with difficulties in deadlines, maintaining efficiency, and adhering to professional standards. Frequent mistakes and difficulties in interpersonal relationships further compound these issues [7]. Finally, ADHD symptoms often interfere with social relationships, romantic partnerships, and marital stability, thus requiring greater effort to maintain a healthy family life.

Adults with ADHD also struggle with time management and organization in their daily lives. They often focus excessively on the present, making it difficult to plan and achieve long-term goals through sustained effort [5]. Given that ADHD frequently persists into adulthood, long-term treatment for adult ADHD is essential. Effective management of adult ADHD has been shown to positively impact academic achievement, occupational success, interpersonal relationships, antisocial behavior, and mood symptoms such as depression and anxiety [8]. While pharmacotherapy is effective in rapidly improving core symptoms of inattention and hyperactivity, it often fails to address every challenge faced by individuals with ADHD [9-11]. Many adults with ADHD continue to experience residual symptoms despite medication, highlighting the need for complementary interventions such as cognitive behavioral therapy (CBT) [12].

CBT plays a crucial role in managing adult ADHD by addressing deficits in executive functioning, such as difficulties with inattention and organization [12]. It positively impacts the ability to maintain structured routines and achieve personal goals while also improving impulse control, organized living, and self-management. Through CBT, individuals learn to observe and analyze their own behavior, thereby reducing impulsive reactions. Additionally, by acquiring skills in planning schedules and setting priorities, individuals can enhance their daily efficiency. CBT aims to identify and modify negative behavioral patterns, helping individuals develop positive behaviors and healthier stress-coping strategies. It enhances self-efficacy by enabling individuals to achieve their goals in daily life systematically, thereby promoting self-confidence and independence [11,13-15].

Group-based CBT involves multiple participants in a collective setting sharing their experiences and addressing core ADHD symptoms using CBT techniques. This approach allows participants to exchange experiences, build empathy for the challenges they face, and gain confidence through mutual support from the group [15]. Despite the benefits of group-based CBT, there are relatively few randomized controlled trials based on well-structured CBT programs. Therefore, we aimed to empirically evaluate the effectiveness of group-based CBT in managing symptoms and improving function in adults with ADHD, thereby providing foundational data to inform long-term treatment strategies for adult ADHD.

A total of 24 participants (10 males and 14 females) completed a group-based CBT program for adult ADHD. The mean age was 27.71±5.92 years and the average age at diagnosis was 24.86±6.89 years. Educational attainment varied, with most participants completing a college-level education (66.7%). Employment status was equally distributed among students (33.3%) and employed individuals (33.3%); 25.0% were unemployed. Most participants were single (66.7%). Nine participants (37.5%) had comorbid mood disorders, including eight with depression and one with bipolar disorder. Most (83.3%) patients received pharmacotherapy. The average FSIQ was 108.14±16.71 (Table 1).

Following the intervention, ADHD symptoms significantly improved, as measured by both the ASRS and K-AARS (Table 2 and Figure 1). The ASRS showed significant reductions across all subdomains, including a decrease in total score from 39.7±8.1 to 28.7±11.6, with both Parts A and B also significantly improved (p<0.001). On the K-AARS, notable improvements were found across all subscales except for hyperactivity. Functional impairment also significantly improved (K-AARS impairment subscale: mean reduction 3.6, p<0.001), reflecting positive changes in daily functioning. To confirm the robustness of these findings, a linear mixed-effects model controlling for demographic and clinical covariates was used, which showed consistent and significant symptom reduction in the ASRS and K-AARS (Table 3).

To explore the role of cognitive ability, participants were stratified into three FSIQ groups: high (≥110), average (90-109), and below average (<90). Significant reductions were observed in ASRS and K-AARS scores in all groups, although the magnitude and consistency varied. The average-IQ group showed the broadest improvements across the subscales, whereas the below-average group showed fewer significant changes (Table 4).

To evaluate the association between treatment adherence and symptom improvement, participants were categorized into three groups based on session attendance: 100% attendance (n=14), 70%-99% attendance (n=8), and <70% attendance (n=2). Both the 100% and 70%-99% attendance groups demonstrated significant improvements across most ASRS and K-AARS domains. In contrast, the <70% group showed minimal changes, with only the total ASRS scores reaching significance (p=0.049) (Table 5).

The impact of comorbid depression was evaluated by comparing outcomes between participants with (n=8) and without (n=15) depression. Both groups showed significant improvements in the ASRS and K-AARS scores, with similar patterns across subscales, except for hyperactivity (Table 6).

Stratified analyses revealed consistent treatment effects across subgroups. Greater reductions in ASRS scores were observed among participants with lower FSIQ scores, whereas the largest K-AARS improvements were observed in the average-IQ group. Participants with full attendance and comorbid depression also showed greater reductions than their counterparts. The detailed results of the subgroup analyses are presented in Supplementary Table 2.

This study investigated the effectiveness of a 10-session group-based CBT program for managing the symptoms of adult ADHD, as measured by the ASRS and K-AARS. The results demonstrated significant improvements across multiple symptom domains on both scales. Importantly, treatment outcomes varied depending on the participants’ cognitive abilities and attendance rates, suggesting that these factors may influence the therapeutic response.

The intervention led to meaningful improvements in inattention, disorganization, and overall functional impairment as measured by the K-AARS impairment index. These symptom domains were strongly associated with academic and occupational difficulties. Notably, the significant improvement in functional impairment highlights the intervention’s real-world effectiveness, as impairment is a core diagnostic criterion for adult ADHD and a primary target for treatment. These findings align with previous meta-analytic evidence indicating that CBT can significantly reduce core ADHD symptoms in adults, particularly inattention and disorganization, which are among the most impairing aspects of the disorder [24,25]. Improvements in these areas are likely to enhance daily functioning, underscoring the clinical value of targeting executive dysfunction in CBT.

Although not included in the DSM-5 diagnostic criteria for ADHD, emotional dysregulation showed significant improvement. Given the strong association with adverse functional outcomes and comorbid emotional disorders, this finding is clinically relevant. Previous research has emphasized the importance of addressing emotional symptoms in ADHD treatment to improve the overall quality of life [26]. These findings suggest that structured CBT may simultaneously address both core symptoms and associated emotional difficulties, extending its benefits beyond symptom reduction to include improved emotional self-regulation [25].

Interestingly, hyperactivity did not improve significantly, which may reflect a developmental trajectory. Previous longitudinal studies have shown that hyperactive behaviors tend to decline or become internalized with age, whereas inattention and executive dysfunction remain persistent and impaired. These findings highlight the importance of focusing treatment efforts on the domains of inattention, disorganization, and emotional dysregulation in order to optimize functional outcomes in adults with ADHD.

Participants with an average IQ (90-109) demonstrated the most consistent and robust improvements. In contrast, those with high IQ (≥110) showed more selective gains, particularly in inattention and APD/CD/ODD, while emotional dysregulation, impulsivity, and disorganization did not significantly improve. This pattern suggests that cognitive ability may moderate treatment outcomes. While higher intelligence is often assumed to enhance responsiveness to CBT, the empirical findings remain mixed. For example, Haaga et al. [27] found no linear relationship between IQ and CBT outcomes in patients with mood and anxiety disorders, indicating that higher intelligence alone does not consistently predict better therapeutic outcomes. Similarly, Mostert et al. [28] reported that adults with ADHD and IQ ≥115 showed fewer executive function deficits, potentially due to compensatory strategies, which may reduce the observable benefit of structured CBT. Participants with below-average IQ (<90) also showed meaningful improvements, although the effects were less pronounced than in the other groups. Due to the small sample size, these findings should be interpreted with caution. Nevertheless, these results are consistent with previous research suggesting that individuals with lower cognitive ability may experience reduced benefits from CBT, likely due to the cognitive demands involved [29]. Overall, these results highlighting the importance of considering cognitive profiles when implementing CBT for adult ADHD. While the intervention appears to be broadly beneficial, tailoring the approach based on cognitive capacity may optimize treatment outcomes.

Treatment adherence, as reflected by session attendance, emerged as a critical factor influencing the therapeutic outcomes in this study. Consistent with prior research showing a dose-response relationship between CBT session exposure and symptom improvement in adults with ADHD, our findings demonstrated that the degree of improvement varied by attendance level [19,30,31]. Participants with full attendance exhibited broader and more consistent symptom reductions, particularly in executive functioning domains such as disorganization and emotional dysregulation. In contrast, even partial absences (e.g., missing one or two sessions) were associated with diminished gains in these domains. These results underscore the cumulative value of attending all sessions in a sequentially designed CBT program, in which later modules build upon earlier skills. As highlighted in previous studies, the acquisition and generalization of CBT techniques require repeated rehearsal and sustained exposure to core strategies [14]. High session attendance may therefore reflect treatment engagement and sufficient exposure for skills to consolidate and translate into real-world improvements. These findings underscore the importance of maintaining treatment adherence throughout the intervention. Strategies such as motivational support, flexible scheduling, and booster sessions may benefit adults with ADHD experiencing organizational difficulties. Moreover, as noted by Skliarova et al. [32], session attendance may serve not only as a proxy for treatment engagement, but also as an indicator of how participants perceive the relevance and utility of the intervention.

Given the prognostic importance of psychiatric comorbidities in adults with ADHD, we conducted an additional analysis to examine whether comorbid depression moderated treatment outcomes. The results showed that CBT was equally effective regardless of the depression status, supporting prior evidence that comorbid depression does not diminish the efficacy of CBT in reducing ADHD symptoms. Previous studies have shown that CBT remains effective even when controlling for depression severity [11]. Furthermore, high session attendance has been associated with greater symptom improvement irrespective of comorbid depression [24], whereas severe depression has been linked to poorer outcomes, possibly due to reduced adherence [33]. The current findings may partially reflect sample characteristics and selection effects, as participants with stable depressive symptoms were more likely to enroll and complete the program. Those with severe or untreated depression may have been excluded or may have dropped out early. Although depression severity was not formally assessed, the high session completion rate suggests that most participants were in a clinically stable condition, which may have contributed to the consistent treatment responses observed across the groups.

Despite the significant contributions of this study, several limitations should be considered. First, it used a retrospective chart review design. While this design allows for real-world assessment of a clinical program, it inherently limits control over confounding variables and introduces potential selection bias. These limitations should be considered when interpreting the findings. Second, the study did not include a control group, which limited the ability to compare and verify treatment effects. However, the primary objective of this study was to evaluate the pre- and post-treatment changes in ADHD symptoms following group CBT, and clinically meaningful results were confirmed using this approach. Third, changes in ADHD symptom were assessed solely using self-report measures (ASRS and K-AARS), which may have been subject to response bias. However, while previous studies have assessed impairment in ADHD symptoms using measures such as CGI-S34 or adult attention-deficit/hyperactivity disorder quality of life scale35 the significance of this study lies in the fact that it is the first to evaluate the severity of impairment based on DSM-5 diagnostic criteria using the impairment subscale of K-AARS. Future studies should include clinician-rated or multi-informant assessments to improve objectivity. Fourth, although the relatively small sample size affected the generalizability of the findings, this exploratory study provides valuable foundational data. Future studies should adopt randomized controlled designs with larger and more diverse samples to validate and extend these results. Lastly, although comorbid mood disorders such as depression and bipolar disorder were identified, the severity of depressive symptoms was not assessed; however, the participants’ ability to attend and complete the majority of CBT sessions suggests that their depressive symptoms were likely well-managed and not in an acute or severe state.