Health-related quality of life and burden of illness in adults with newly diagnosed attention-deficit/hyperactivity disorder in Sweden

Attention-deficit/hyperactivity disorder (ADHD) is estimated to affect between 2.5 and 5.0% of adults worldwide [1‐3]. Although originally considered to be a disorder of childhood, ADHD is now recognized to persist into adulthood in approximately 65% of cases [4‐7]. While many adults with newly diagnosed ADHD may have experienced symptoms as children [6], two recent studies have suggested that, in some cases, ADHD symptoms may not manifest until adulthood [8, 9]. Results from a study in Sweden demonstrated that the number of adults diagnosed with ADHD increased year on year from 2006 to 2011 [10], and in 2013 ADHD was diagnosed in 2.7% of adult psychiatric patients in Sweden [11]. Despite the increasing recognition of ADHD in the adult Swedish population, a recent registry study reported that patients with psychiatric symptoms may undergo years of treatment before receiving an ADHD diagnosis [11]. Nylander et al. found that diagnosis of ADHD in adults took, on average, 3 years from the initial point of contact with psychiatric services, although in some cases diagnoses were delayed for as long as 10 years [11]. Delays in diagnosis were particularly apparent if the signs and symptoms of ADHD were attributed to other psychiatric disorders, for example, anxiety disorders, which often co-occur with ADHD [11]. These findings highlight the need for increased recognition and understanding of ADHD as an adult psychiatric disorder. Similarly, the European Network Adult ADHD published a consensus document in 2010, with the aims of increasing awareness of ADHD in adults and improving patient care across Europe [12].

The effects of ADHD can have a significant negative impact on many aspects of adult life, from social and emotional well-being to professional development and financial security [13, 14]. Despite this, few studies have investigated the burden of disease in adult patients with ADHD. Swedish patient records and archives provide a rich source of data for investigating burden of illness in adults with newly diagnosed ADHD. The diagnostic procedure for adults comprises a clinical interview to assess the frequency and duration of ADHD symptoms, as well as a full neuropsychiatric investigation of functional impairments from both clinical and social perspectives. This retrospective chart review study utilized the five-dimension EuroQol questionnaire (EQ-5D) [15] to develop a predictive model of health-related quality of life (HRQoL) in adults with newly diagnosed ADHD, based on their ADHD symptoms, psychiatric comorbidities, and socioeconomic characteristics.

Adult patients with newly diagnosed ADHD experienced a considerable disease burden and substantially impaired HRQoL in this retrospective chart review. Psychiatric comorbidities were common in the study population, and linear regression analysis identified comorbid anxiety and depression as key factors contributing to poor HRQoL. MADRS-S score was the strongest predictor of EQ-5D index score, implying an association between severe depression and poor HRQoL in adult patients with ADHD. Other variables, including low educational attainment, low levels of employment, and female sex were also associated with poor HRQoL in the study population.

Both the strengths and weaknesses of this study should be considered when interpreting the results. The study included a moderately large number of patients and integrated in-depth analyses of patients’ neuropsychiatric evaluations with a variety of patient- and clinician-reported measures, including HRQoL. The variety of information extracted from the EMRs enabled the investigation of a wide range of potential factors impacting HRQoL in adult patients with ADHD. HRQoL was assessed using the EQ-5D, a validated generic HRQoL tool that provides health utility estimates and is recommended by the UK National Institute for Health and Care Excellence [22]. The use of the generic EQ-5D permits comparisons with reference populations and patients with other diseases [22].

There are, however, several limitations that should be noted. First, data for some parameters were missing for a substantial proportion of patients, which may have introduced bias. To address this, a multiple imputation model was utilized to estimate missing data for the regression model. However, this method may also influence results, particularly when sample sizes are limited. Data were missing for fewer than 20% of the total patients across both sites for all imputed variables except ASRS-v.1.1 score, which was missing for 88% of Liljeholmen patients (Additional file 1: Table S1). This implies that the ASRS-v.1.1 may not be part of the routine diagnostic procedure at Liljeholmen. The high proportion of imputed data for this variable in the linear regression model precludes any reliable conclusions concerning the relationship between ASRS-v.1.1 score and HRQoL in adult patients with ADHD. Secondly, covariates for the statistical models were selected based on the data available, but other factors influencing HRQoL may not have been captured in the study. Thirdly, comorbid psychiatric diagnoses were based on the MINI for all psychiatric disorders except autism. Inclusion of autism as a separate covariate in the analyses may have led to underestimation of the impact of psychiatric comorbidities on patients’ HRQoL. Other limitations to consider are the absence of a comparative control sample of EQ-5D index scores from the Swedish population and the recruitment of patients only in the city of Stockholm.

The findings of the present study strongly suggest that adult patients with ADHD experience reduced HRQoL, and support the conclusion that the manifestations of ADHD are associated with considerable disease burden. The mean EQ-5D index score in the patient population was 0.63 (SD, 0.28), which is markedly lower than published EQ-5D index scores for the healthy adult population in Sweden (range, 0.74–0.89) [23] and in the UK (mean, 0.86; SD, 0.28) [24]. Similarly, low EQ-5D index scores have been reported for patients with other chronic conditions including asthma, chronic obstructive pulmonary disease, diabetes, epilepsy, heart failure, and stroke (overall mean index score, 0.73) [25]. The mean EQ-5D index score in the present study is also within the range reported in a systematic review of HRQoL in adults with psoriasis (0.52–0.9) [26], but higher than that reported for people with spinal complaints (0.39) [27]. The applicability of the present study’s findings to cultural/social groups outside Stockholm is uncertain, although a recent study involving seven countries concluded that the impact of ADHD on patient well-being is consistent across different socioeconomic groups [13]. Furthermore, the EQ-5D scores in the present study are similar to those reported for adult patients with ADHD in other European countries [28, 29], suggesting a broad relevance of the present findings.

To our knowledge, this is the first study to use linear regression to identify specific factors that may influence HRQoL in adult patients with ADHD. Comorbid anxiety and depression, together with patient-rated severe depressive symptoms, were identified as the strongest predictors of poor HRQoL. Given that these diagnoses are frequently comorbid with ADHD, the potential negative impact of these disorders upon patients’ HRQoL should be considered in their clinical management. Adjusted mean EQ-5D index scores were also significantly higher in men than in women, who made up 57% of the patient population. A preponderance of women is uncommon in studies of ADHD, which is diagnosed more frequently in men than in women [2]. Gender is not thought to modulate the phenotypic presentation of ADHD [30], but higher rates of comorbid anxiety disorders have been reported in women than in men [31], which could contribute to the gender difference in HRQoL in the present study.

Psychiatric disorders other than depression and anxiety were common, affecting 19% of the patient population. However, only 3% of the patients in the present study were diagnosed with comorbid bipolar disorder. This is in contrast with the results of the National Comorbidity Study which reported a bipolar disorder prevalence of 19.4% among adults with ADHD [32]. It is possible that the unusually low frequency of bipolar disorder may have influenced the relationship between comorbid psychiatric disorders and HRQoL in the present study, and further studies in patients with comorbid bipolar disorder may be warranted. Over two-thirds of the patient population (77%) also reported at least one somatic comorbidity. Pain was the most frequently reported somatic comorbidity. Individuals with ADHD are more prone to accidents and injuries [33], may be more sensitive to pain [34], and may experience motor inhibition problems and heightened muscle tone [35]. Multiple studies have identified a high incidence of joint hypermobility in individuals with ADHD [36], which may also have contributed to the high prevalence of pain in the present study. Adults with ADHD are more likely to have somatic disorders, and are more likely to use non-psychiatric healthcare services, than those without ADHD [37]. In particular, somatic disorders such as obesity, sleep disorders, and asthma frequently co-occur with ADHD [38]. ADHD symptoms and functional impairment may make people with ADHD more vulnerable to somatic diseases and may affect their ability to obtain appropriate diagnosis and treatment for somatic disease. Optimum care for patients with ADHD may involve an integrated and multidisciplinary approach for identifying and treating co-occurring psychiatric and somatic disorders [39].

Other predictors of poor HRQoL included poor educational achievement and not having a main income derived from employment. In the present study, primary school was the highest level of education reached for 37% of adults with newly diagnosed ADHD, and only 13% were educated to university level. In comparison, equivalent levels in the general Stockholm population in 2014 were reported to be 16 and 45%, respectively [40]. Having an average or higher intelligence score (denoted by a WAIS-IV score of more than 85) was not significantly associated with improved HRQoL, implying that the challenges faced by patients with ADHD in school extend beyond deficits in intellectual functioning. The present results also suggest that difficulties continue into the workplace. Despite a median age of 33 years, fewer than half of the patients were able to support themselves financially through employment or self-employment, and 22% were reliant on sickness benefit as their main source of income. Thus, the present study highlights the significant impact that poor performance in school and the workplace can have on HRQoL and emphasizes the need for early diagnosis and effective clinical management of ADHD symptoms from a young age. The present study was not designed to investigate the impact of ADHD medication on HRQoL in individuals with ADHD, but a recent systematic review concluded that ADHD medication may help to reduce functional impairment and to improve HRQoL deficits [41].

European guidelines recommend an individualized, multimodal approach to treatment of ADHD in adults, including psychological treatments and medication [12]. In the present study, over two-thirds (77%) of patients were prescribed pharmacological treatment for ADHD. This figure is in line with guidance from the Swedish National Board of Health and Welfare indicating that ADHD medication is likely to be effective and appropriate in the majority of patients [42].

In summary, the findings of this non-interventional, retrospective study indicate that undiagnosed ADHD contributes to poor HRQoL in adults presenting with psychiatric symptoms. Furthermore, the impact of ADHD on HRQoL may be exacerbated by psychiatric comorbidities such as anxiety and depression. Adults with newly diagnosed ADHD and comorbid depression or anxiety may require particular care and resources in their management.