Reaching ADHD Treatment Targets?

Abstract

In a recent epidemiological study, Grøntved et al. present important results on the temporal changes of the rates in prevalence and incidence of ADHD diagnosis and use of ADHD medication in Denmark over the past two decades [1]. The authors have applied stringent, robust, and sound methods in analyzing individual-level data available from the Danish nationwide registers. Their main findings include consistent increases in the prevalence and incidence of diagnosis of ADHD and corresponding increases in pharmacological treatment across sex and age groups from 2000 to 2022. The most notable increase in recent years is observed in young adult women. They found that 3.03% of the total population living in Denmark was given a clinical diagnosis of ADHD or had received treatment with ADHD medication in 2022. Among children and adolescents aged 6–18 years, it was 4.0%; in adults aged 18–27 years, it was 7.1%; in adults aged 27–35 years, it was 6.1%; and in adults aged 35–50 years, it was 3.5%, all as observed in 2022.

The study offers valid and precise estimates of the number of individuals diagnosed with ADHD or treated with ADHD medications within the entire Danish population and of the increases in those rates over a 20-year period. Such high-quality population-based estimates of the yearly prevalence and incidence of ADHD are much needed, as these measures of occurrence focus on the absolute risk, answering the question “What is the actual percentage?” Many articles in news media [2, 3] and also some scientific studies [4] only focus on the relative increase in number of diagnosed or treated over a certain time period, not on the prevalence rate. Similarly, a former Minister of Health in Denmark [5], and some governmental reports from authorities have raised concerns about the relative increase in the use of ADHD medication, while others have reported incorrect prevalence rates of clinical diagnoses of ADHD, as they have relied on too simplistic methodologies [6]. The study by Grøntved et al. overcomes such methodological limitations and reports valid and less biased estimates of the rates of prevalence and incidence of ADHD diagnosis and treatment. This is important, because in order to evaluate whether there is reason for concerns about over-diagnosing or overtreatment of ADHD, one needs to compare the rates of diagnoses and use of ADHD medication with the expected occurrence of the disorder.

Studies on the underlying occurrence of ADHD in the population suggest that 6%–7% of all children and adolescents fulfill diagnostic criteria for the disorder [7], and the occurrence in the population seems to have been stable for several decades [8, 9]. In adults, 4%–5% of the population fulfill diagnostic criteria for ADHD [10]. These studies also show that children and adolescents fulfilling diagnostic criteria for ADHD are less common in girls than in boys (1:2 sex ratio), whereas in adults there is no difference (sex ratio 1:1).

Hence, the prevalence rate reported by Grøntved et al. on the diagnosis of ADHD in children aged 6–18 years (4.02% in total; 2.7% in females and 5.3% in males) is a little lower than the expected occurrence of the disorder, and the sex difference is as expected (1:1.97). These results concur with previous findings [11] and are reassuring as they suggest that in Denmark, ADHD is not over-diagnosed nor overtreated among children and adolescents, as it may be in some countries, such as the United States, Canada, and Iceland [12-14]. In many of those countries, children who are the youngest in their class are more likely to be diagnosed with ADHD or treated with ADHD medication as compared to the eldest in the class [15]. Denmark is one of the few countries where such associations were not found [16, 17].

In contrast, the prevalence of ADHD among adults aged 18–35 years reported by Grøntved et al. (6%–7%) may raise some concern, as this is slightly above the expected rate. In 2012, the prevalence in males aged 18–27 years had reached the expected 4%–5% already, and in females it was reached in 2019. Still, the incidence of ADHD in that age group has continued to increase in both sexes, especially so in females. The high increase in incidence of ADHD among young adult females observed within the last 5 years is likely linked with the fact that for decades girls with ADHD were less likely to be identified and diagnosed [18], as it was previously considered a childhood disorder only affecting boys. When these misconceptions eventually were rectified, it meant that many girls were diagnosed as teenagers [19], and this diagnostic delay in part also explains the sharp increase in the incidence that we now see in adult females.

The study by Grøntved et al. supports previous research documenting that in Denmark, ADHD is not over-diagnosed or overtreated in children and adolescents. This is likely related to the fact that most children are diagnosed at regional hospital departments, after extensive interdisciplinary assessments [20] by medical doctors trained as specialists within child and adolescent psychiatry, clinical psychologists, nurses, and social workers, and often also pedagogical staff performing direct observation of the child in its everyday environment. So in Denmark, we seem to reach the target in diagnosing and treating ADHD among children and adolescents.

Clinical assessment of ADHD in adults can be a challenging task. Diagnosis currently relies on clinical interviews and self-report or informant-report scales, which are vulnerable to bias and malingering, increasing the risk of misdiagnosis. Further, it is often difficult to obtain valid information on the severity and number of ADHD symptoms, and on the level of impairment the person experienced in childhood. Despite these challenges, most assessments of adults with ADHD are not performed by an interdisciplinary team, as it is the case for most children and adolescents. Rather, most adults are diagnosed by psychiatrists in private practices, often based on a mono-disciplinary assessment. Furthermore, assessment of adults with ADHD was only recently included in the training to become a licensed psychiatrist [21], in spite of many psychiatrists experiencing an overwhelming number of referrals for assessment of ADHD [22]. The clear increase in the incidence of ADHD in adults could be linked with this imbalance between the level of need for assessment and the level of capacity, combined with a lack of formal training and too simple diagnostic practices in adult services. The planning of future health services should take this into account, with emphasis on better clinical training of specialists and broader interdisciplinary assessments of adults with ADHD.

A way to improve diagnostic accuracy in adults with ADHD is to develop new technologies and to identify biological markers for improvement. Multimodal approaches combining behavioral and physiological data represent a promising solution to improve diagnostic precision. In particular, recent advances in virtual reality (VR) and artificial intelligence enable more objective, ecologically valid assessments. For instance, attention tasks in immersive VR environments—such as a virtual seminar room with real-life distractors—have been shown to reliably differentiate adults with ADHD from healthy controls [23]. Emerging machine learning models that integrate data from such real-life-like VR scenarios, including cognitive performance, gaze behavior, head movements, and self-reported inattention, may further enhance diagnostic accuracy. Together, these tools enable a shift toward more precise, multidimensional assessment strategies to aid diagnostic accuracy for adult ADHD.

To conclude, the paper by Grøntved et al. concurs with other recent findings and adds new detailed information on this clinically important area. Collectively, data suggest that we have to be aware of potentially overshooting the target among adults, with an increased risk of over-diagnosing and over-treating ADHD in those age groups, especially in females. Such a development is unfortunate, in that it may, for example, jeopardize the availability of services and dilute the significance of the diagnosis. Clinicians should comply with the standards for the assessment of ADHD, as recommended in international guidelines [24]. To avoid the growing risk of over-diagnosing and over-treating adult ADHD, we must ensure that assessments in adulthood cases mirror the interdisciplinary rigor applied clinically in childhood cases, anchored in standardized protocols and strengthened by emerging novel technologies like VR that offer objective, ecologically valid insight into behavior and physiology.

This paper was conceptualized by S.D., who also wrote the first draft. M.B.P., K.W.M., and K.K.C.M. revised the draft, and all four authors approved the final version.

K.W.M. has received honoraria from Lundbeck, Gedeon Richter and Angelini in the past three years. SD, MBP, and K.K.C.M. declare no conflicts of interest.