The socioeconomic burden of adult attention-deficit/hyperactivity disorder in Spain

Data sources

Relevant data regarding the prevalence of adult ADHD in Spain and its impact on the healthcare, social, economic, and legal domains were obtained from the scientific literature using the PubMed search engine and selected based on their representation of Spain or any of its regions, or, otherwise, on study methodology. Thereafter, an Advisory Board of a multidisciplinary group of experts on ADHD, including a hospital psychiatric department chief, a prison health service physician, a hospital psychiatric department psychologist, a mental health service social worker, the director of the ADHD association of patients, and a former hospital manager and psychiatrist, was convened to agree on which of the presented data points were to be included in the socioeconomic model. Whenever experts considered that a data point was not representative of the Spanish adult population with ADHD and/or no alternative data point was available in the scientific literature, especially regarding healthcare resource consumption, assumptions were made.

Population

Estimates of the burden of diagnosed and undiagnosed ADHD were based on prevalence data. Accordingly, to estimate the burden of diagnosed adult ADHD in Spain, a 0.5% prevalence was used (12). Moreover, to estimate the burden of undiagnosed adult ADHD in Spain, the difference between the estimated prevalence of adult ADHD in Spain (3.3%) (4) and the prevalence of diagnosed adult ADHD in Spain (0.5%) was used, yielding a prevalence of 2.8%. Applied to the adult population of Spain (≥18 years) on July 1, 2019 (13), it was estimated that, at the time, there were 1,279,861 adults with ADHD in Spain, of which 193,918 were diagnosed (15%) and 1,085,943 were undiagnosed (85%).

Costs

The economic model included two types of costs, one-time and recurrent annual costs, given the characteristics of the first, which are timely and lack an annual frequency. Costs are of tangible and/or intangible nature, the latter of which were estimated from financial proxies (e.g., willingness to pay for an effective alcoholism therapy). Overall, healthcare costs were estimated by multiplying the number of annual resources consumed by their unit costs, while the remaining costs were estimated by further applying prevalence reference data (e.g., multiplying the prevalence of addictions in patients with ADHD by the number of annual addiction therapy consultations and their unit cost). Estimates of the healthcare burden associated with ADHD medication were based on the cost of treating an average patient with each one of the active agents used to treat ADHD and their market share (14), considering that between 10.0% and 27.3% of adult patients with ADHD are undergoing treatment (based on estimates by the Advisory Committee and Takeda, respectively). For each active agent, the presentations with the maximum daily dose as detailed in their summary of product characteristics were selected (15-17), and among them, the ones with the lowest cost per mg (retail price + taxes) (18). Moreover, costs associated with labor productivity were estimated using the human-capital method, by which work time lost as a result of illness is valued at the market wage. A detailed description of the variables and unit costs included in the socioeconomic model has been provided in Tables 1 and 2.

Unit costs were obtained from the median rates for health services published in the official bulletins of the Spanish Autonomous Communities, official statistics (published by the Spanish National Institute of Statistics and the Spanish Ministry of Health, Consumer Affairs, and Social Welfare), the scientific literature, and market prices. Prices were updated to 2019 Euro according to the corresponding general or medical Consumer Price Index (19), except for medication costs, which were obtained on September 10, 2020, from the medication database of the General Council of Official Associations of Pharmacists.

Results are presented as mean costs per adult patient with ADHD and total costs of ADHD within domains, broken down into one-time costs and recurrent annual costs. Moreover, to estimate the burden of ADHD on the healthcare system, the analysis was broken down into three distinct time periods to account for differences in resource consumption: diagnosis, post-diagnosis follow-up (first year), and post-diagnosis long-term follow-up (following years). While the diagnosis time period and the first year after diagnosis incurred one-time costs, the following years were associated with recurrent annual costs. Results are also presented as total costs of adult ADHD in Spain, which were obtained by multiplying the mean cost per patient by the prevalence of diagnosed and/or undiagnosed ADHD according to the bottom-up method (4,13). Given the lack of studies on the consumption of healthcare resources by undiagnosed adults with ADHD, the one-time and annual total cost of undiagnosed ADHD was obtained by excluding healthcare costs from the one-time and annual cost per adult patient diagnosed with ADHD and applying such costs to the estimated number of undiagnosed adults with ADHD.

Sensitivity analysis

A sensitivity analysis on assumption-based data points was carried out to account for worst and best-case scenarios, relative to a reference scenario (Tabs 1 and 2).

Healthcare burden

The estimated cost per adult patient with ADHD to establish a diagnosis amounted to €577, increased up to €3,534 in the first year following diagnosis, and slightly decreased to €3,396 per year during the following years. Costs associated with hospitalizations accounted for approximately 50% of the burden on the healthcare system for both the first and the following post-diagnosis years (Fig. 2A).

Social burden

The estimated cost per adult patient with ADHD within the social domain amounted to an annual cost of €4,438 and a one-time cost of €431. Costs associated with substance abuse accounted for 74.23% of the annual social burden, specifically those associated with smoking (46.20%) and alcoholism (21.20%). In addition, problems with intimate relationships accounted for 16.44% of the social burden. Moreover, the cost of a divorce at any given time in the patients’ life further contributed to the overall social burden (Fig. 2B).

Economic burden

The estimated cost per adult patient with ADHD within the economic domain amounted to an annual cost of €7,795, of which 53.35% were costs associated with work absenteeism, followed by wage reductions with respect to those without ADHD (31.76%) and work presenteeism (11.46%). One-time costs were not identified within this domain (Fig. 2C).

Legal burden

The estimated cost per adult patient with ADHD within the legal domain amounted to an annual cost of €23 associated with traffic tickets. Most importantly, one-time costs amounted to €3,351, of which 62.23% were associated with imprisonment and 32.78% with driving license withdrawals at any given time in the patients’ life (Fig. 2D).

Sensitivity analysis

Overall, the results of the sensitivity analysis showed that recurrent annual costs associated with diagnosed adults with ADHD could vary up to 6%, while one-time costs could vary up to 21% with respect to the reference scenario. More specifically, one-time costs associated with the legal domain could vary up to 39% with respect to the reference scenario (Tab. 4). This large variation within the legal system was primarily associated with variations in the percentage of patients with ADHD who have ever been imprisoned (3.5% to 15%). Moreover, the mean cost per day of imprisonment depends on the number of years that the patient spends in prison, which could further increase variability.

This is the first report on the socioeconomic burden of adult ADHD in Spain (7). The results highlight a large socioeconomic impact, which was estimated to incur an annual cost of €15,652 and a one-time cost of €7,893 per adult patient diagnosed with ADHD (€3,035 million and €1,531 million for Spain, respectively). Given the large rates of adult ADHD underdiagnosis, estimated at 2.8% (4), the socioeconomic impact is expected to be much higher (at least €13,309 million and €4,107 million, respectively). These results are not easily comparable to previous studies on the economic burden of ADHD. A recent systematic review on the global economic burden of ADHD reported a large variability across countries possibly associated with differences in healthcare systems, resource utilization, cost components, populations, and data sources (7). Therefore, any comparisons with previous studies should be interpreted with caution.

Overall, the estimated total annual cost per adult patient diagnosed with ADHD in Spain was above previous reports ranging between $US 831 (€536) to $US 20,538 (€13,247) per person (7,20). Moreover, the present study included one-time costs that increased the overall burden of adult ADHD in Spain, providing a more holistic estimate of costs. However, while previous studies on the economic burden of ADHD have typically focused on only one aspect of cost (e.g., healthcare costs) (7), the present study examined the burden of adult ADHD from a multidimensional perspective, estimating costs incurred within the healthcare, social, economic, and legal domains. Particularly important for adults with ADHD, this multidimensional analysis provides a more comprehensive description of the burden and may prevent the underestimation of costs (2,7). However, it should be noted that overestimation of costs was also prevented by taking a conservative approach within the analysis (e.g., costs that could possibly be incurred by undiagnosed adults with ADHD were not quantified, such as healthcare costs derived from traffic accidents, fights, or drug consumption).

The results of previous studies that considered costs within four major domains (direct costs, indirect costs, education system costs, and justice system costs) closely resembled those reported in the present study. Accordingly, an annual cost per person of $US 20,538.95, of which 72% was attributed to work-related productivity costs, has been previously reported (7). Moreover, Sciberras et al (21) reported an annual cost per person of $US 15,664 of which 81% was attributed to work-related productivity costs. Though the latter estimated costs across the lifespan, the majority of costs were associated with adulthood (21). As the results of these studies, the estimated annual cost per patient in the present study was mainly attributed to work-related productivity costs within the economic domain (i.e., costs associated with mean wage reductions compared to non-ADHD, absenteeism, and presenteeism). However, only 45% of published studies on the economic burden of ADHD have captured indirect costs (i.e., work-related productivity) (7).

On the other hand, healthcare costs have been widely studied within economic burden studies (7). In this domain, the present study estimated an annual cost of €3,395.83 (21% of the total annual costs) and a one-time cost of €4,110.88 (52% of the total one-time costs) per patient diagnosed with ADHD. The latter included all medical consultations leading to diagnosis and those of the first-year post-diagnosis follow-up, contributing to the large one-time healthcare costs. However, these costs may be compensated with an appropriate treatment, which may have an impact on costs within other domains. Moreover, medication was estimated to be only 10% of the annual healthcare costs. This is particularly important for undiagnosed (i.e., untreated) adults, which accounts for 85% of adult patients with ADHD in Spain (4,13). In this regard, previous studies have shown that appropriate medication may reduce the risk of substance abuse (22,23), criminality (24), traffic accidents (25), and suicide attempts (26) in patients with ADHD, which may positively impact work-related productivity and other economic and/or legal issues.

However, the results of this study should be interpreted with caution given its limitations. First of all, the estimated burden of adult ADHD applies specifically to Spain and is therefore not representative of other countries. Within the healthcare domain, the large variability reported for the management of ADHD across regions of Spain may infer a large variability of costs as well. However, the present study did not include an interregion analysis of costs, which should be considered in future studies. Notwithstanding, a reasonable range for the consumption of healthcare resources was included in the sensitivity analysis to account for this variability. Moreover, healthcare costs incurred were mainly associated with ADHD follow-up and treatment and as such were only applied to adult patients with an ADHD diagnosis (0.5%) (12) for the estimation of total costs. Therefore, total costs incurred by adults with ADHD who are yet to be diagnosed and treated were underestimated, as the healthcare domain was not accounted for in these patients. Accordingly, future studies are encouraged to estimate the burden of adult ADHD before and after diagnosis, as it was not possible in the present study given the lack of scientific literature on the matter. Moreover, future studies should consider ADHD as a lifespan disorder in which any action taken during initial stages may drastically affect the course of the disorder and its burden (8).