QoL is being increasingly recognized as an important component of a comprehensive assessment of the impact on children and young people of health problems, in general, and ADHD, in particular. However, the QoL concept remains problematic in a number of ways, with multiple competing definitions and measurement approaches [18
]. These issues complicate the interpretation of the existing data relating to QoL in ADHD. Notwithstanding these limitations, in the current review we have brought together the existing published data on QoL in ADHD. This allows us to assess the implications of these findings, reflect on issues of interpretation and identify areas for future study.
The current published evidence indicates that QoL is impaired in children with ADHD according to parental report. Across different measures of QoL parents consistently rate the QoL of their children with ADHD as between 1.5 and 2 SD below the appropriate population norms. Furthermore the evidence suggests that QoL impairment increases as the severity of disorder increases, and/or where it is complicated by the presence of comorbidity or psychosocial stressors. The most robust effects are found on the psycho-social
related measurement scales and those that assess impact on family life. Both inattentive and hyperactive/impulsive ADHD symptoms appear to be equally related to this reduction in QoL. Furthermore, there is evidence to support treatment effects on QoL that to some extent mirror their effects on ADHD symptoms, although with smaller effect sizes. While there is some evidence for child reported reductions in QoL this is less consistent than for parent ratings. There is also fairly consistent evidence that parents and children assess QoL differently, as evidenced by the, modest, correlations between parent and child reports, and that parents tend to rate their children with ADHD as having lower QoL than do the children themselves. While these may in part be related to the measures used (neither of the studies that used the child rated CHQ reported differences between ADHD and healthy children but all four of those that used other scales did) there are several other factors that could account for these findings. Inconsistencies between child and parent ratings of QoL may also reflect age, or sample differences as well as error or true differences. In contrast to children with other psychiatric conditions (e.g., depression), children with ADHD may have an over-optimistic view of their situation. A similar effect has been demonstrated in many studies of self-esteem and self-concept in children with ADHD where it has been hypothesized as being the result of a positive illusory bias
]. Children with ADHD are hypothesized to overestimate their own abilities and performance in order to protect a positive self-image [54
]. Experimental studies have supported aspects of this proposed mechanism [35
] and it may be important for similar studies to be designed with respect to child reports of QoL in ADHD. Klassen et al. [39
] have suggested several other possible reasons for the discrepant findings between child and parent reports of QoL; children may want to conceal their problems; they may ignore them in an attempt to cope with them; they may undergo a process of adaptation to disorder leading to a shift in their internal standards leading to changes in evaluation; they may be making systematic mistakes in rushing through the questionnaires because of their impulsive cognitive style. The finding of larger discrepancies between self- and parent-ratings in children with comorbid ODD/CD and those with additional psychosocial stressors may support the first two hypotheses. This pattern of discrepancy between informants also raises a fundamental conceptual issue given that, in its purest sense, QoL has a strong element of self evaluation. If this view was taken to its logical conclusion the child’s view would trump that of the parents. However, at this stage we suggest that a pragmatic approach should involve attempts to develop methods that allow the combining of both proxy and child ratings in order to provide a more comprehensive and integrated assessment [83
]. There will, however, need to be more work exploring the psychometric properties of child-report instruments both in general and in ADHD specifically. Future research, including head to head comparisons of parent and child ratings and experimental studies, should also address the differing ways by which children and parents construct the experience and impact of ADHD on the child’s QoL. Developmentally sensitive designs that can describe the impact of ADHD on QoL at different ages and the progression of QoL over time would also be very welcome. Large datasets, particularly those derived from community samples, should also be interrogated using data reduction techniques such as factor analysis to identify latent variables. Of particular interest will be studies that have used more than one measure of QoL whereby commonalities between different measures can be identified and possibly translated into new instruments with improved validity and reliability.
Relatively few child studies have compared QoL in ADHD either with QoL in other psychiatric disorders or with chronic physical disorders. Those studies that have been conducted have started to suggest that different disorders may result in different QoL profiles, however, more and larger studies will improve our understanding considerably.
More work is also required to improve our understanding of both the differences and interrelationships between the different levels of analysis that comprise a child’s overall functioning (e.g. ADHD symptoms, associated functional impairment and QoL) as these concepts are currently not well delineated either theoretically or on a practical level within the different measurement scales. Different questionnaires contain different mixes of items which tap into all three levels. This means that there is inevitably item-overlap between symptoms rating scales and QoL measures and it then becomes difficult to tease out any independent effects that the disorder or its treatment may be having on symptoms on the one hand and QoL on the other. This in turn begs the question as to whether an apparent treatment related change as measured by current QoL instruments actually adds anything to our understanding of treatment effects. Whilst we believe that measures of QoL can add considerable colour to the measurement of treatment outcome future research needs to address the contribution of these different elements in characterizing ADHD and its relationship to QoL. A major question to be addressed here would be; does the concept of QoL add any value to our understanding of ADHD over and above the concepts of symptoms and more specific functional impairment? One study [74
], explicitly studied aspects of this overlap and reported that the removal of potentially overlapping (symptom) items made little difference to the relationships between mental illness and QoL that they had previously established. There is the potential for similar analyses to be conducted with existing datasets and this may help to provide a more definitive answer to this question. This may suggest ways that the existing measures of QoL could be refined for use with ADHD populations or scored differently when used in this group. This may also result in a clearer delineation of the key characteristics that lay at the core of QoL that are independent of both symptoms and general functional impairment.
Even within the currently limited research into QoL in children with ADHD there is a lack of consistency in terms of the instruments used to measure QoL. These different instruments have been organized into substantially different sub-scale structures and content [18
] which has made it very hard to compare QoL across studies and disorders. These differences between the instruments and between researchers regarding their preferred measure are likely to reflect different opinions regarding the best conceptualization of QoL and emphasize the lack of an agreed core QoL paradigm. Sufficient data has not yet been published to perform a meaningful meta-analysis of studies and instruments from which steps could be taken towards the development of a core set of items that could in turn lead to the development of a common instrument. Of course as is frequently the case in psychological research the authors of the current measures of QoL will often have substantial academic and/or financial investment in their own tool and may therefore also be reluctant to engage in a process by which their own measure may be used less frequently in future studies. While it is not possible at this stage to recommend one measures as being superior to the others it would be beneficial for studies to be conducted that compared different measures in head to head designs in order that their performance in different groups and different contexts can be described. Studies in children and young people with ADHD that combine questionnaire and interview methods would also be helpful to support the validity of these measures in this group.
Most studies to date have relied on clinic-referred samples, and thus have the potential for referral and Berkson’s bias [9
]. This has led to a reduced range in outcomes and associated limitations on the power of statistical tests. Further studies are required, to anchor these effects within the wider population.
Most studies have used parental reports both for symptom severity and
QoL. This introduces the problem of shared-rater variance and may induce at least two possible sources of bias. This could result in a spurious association between ADHD symptoms and QoL and leaves both measures open to undue influence by parent characteristics: other than the very general data from the ADORE study mentioned above [68
], we are unaware of any studies that have investigated the effect of parental mental health on measures of their child’s QoL. Future studies should, as a matter of course, take independent ratings of QoL and symptoms. The choice of who should act as the second informant itself raises a number of issues. In the broader field of ADHD, teachers’ ratings are often used to address this problem. However, the low correlations found between ratings of QoL by the child or parent and teacher-reported symptoms may be accounted for by the fact that teachers are interested in and observe different maladaptive and adaptive behaviours in the classroom than parents do at home, or that they often only see the children when they are medicated. On the other hand, it is also possible that parents may have exaggerated both symptoms and impact on well-being.
Finally, treatment studies have, to date, been extremely limited in their scope. Studies have focused almost exclusively on one treatment modality (pharmacological) and one molecule (atomoxetine). Stimulants (amfetamines, methylphenidate) are also recommended for the treatment of ADHD [4
]. In view of the many measurement issues described above we are not yet at a stage whereby QoL measures can be considered as serious contenders as primary outcome measures in major clinical trials although this may change in the future. One particular psychometric issue that requires clarification in this respect is clarification of what constitutes a clinically meaning change for these measures. We do, however, strongly recommend that those designing and conducting future clinical trials, both pharmacological and psychosocial, should include measures of QoL as secondary outcome measures. Although we are aware of several ongoing RCTs of stimulant medication that are using QoL measures at present no systematic published data from RCTs on the impact of methylphenidate on QoL in ADHD, only one RCT of amfetamines and none with psychosocial treatment, this needs to be addressed urgently. It should also be noted that the total number of individual children that have had their QoL measured as a part of the atomoxetine development program is less than it may initially appear to the casual reader. Several of the meta analyses have included data from the same trials and all of the children in the long term open label follow-up study described by Perwin et al. [58
] were enrolled into the long term study following their having completed participation in an RCT and are therefore likely to be included in at least one other publication. The lack of systematic studies of psychological therapies either on their own or in multimodal combinations with medication is a further omission in our understanding of the impact of treatment on QoL.
Studies have, on the whole, had relatively short follow-up periods and it may be the case that some aspects of QoL will take more time for change and would therefore not be seen in these short-term clinical trials. However, Perwien et al.’s longer term study [58
] failed to show any additional improvement in QoL after the acute treatment period.
There has been no systematic analysis of the extent to which changes in QoL are mediated by symptom changes, changes in functional impairment or other factors. This task is complicated enormously by the fact that the concept of QoL appears to be somewhat confounded in current scales with ADHD symptoms and functional impairment.
Although it is likely that QoL, in relation to medication response, will probably be influenced by a mixture of positive treatment responses and side effects the role of adverse events, in determining QoL following treatment, has not yet been reported in any of the published studies.
Most studies have either had strict inclusion and exclusion criteria that have not allowed the recruitment of those with comorbid disorders or have failed to control for comorbid disorders such as ODD, anxiety and depression, either at baseline or when assessing the responsiveness of QoL to treatment, even though it is recognized that several subscales of the QoL measures contain items on behaviour problems, depressive symptoms and anxiety. At the same time, it seems clear that some of the QoL effects demonstrated in ADHD are clearly distinct from ADHD symptoms, e.g. peer and family relation impact.
The ADORE study [61
] collected naturalistic observational data on ADHD symptoms, impairment, comorbidity and QoL over a 2 years period on a large group of children and young people with ADHD who were receiving a wide range of pharmacological and non-pharmacological treatments. Data from the longitudinal portion of this study has been submitted for publication and will help to address many of these issues. However, it is also essential that further well designed clinical trials which utilise both child and parent proxy completed QoL measures are conducted and in particular head-to-head studies of different treatment packages with a broad range of outcomes over extended periods of time, with multiple testing points are required. These studies should be designed in such a way to allow the exploration of the natural history of changes in QoL following treatment as well as the mediating effects of symptom reductions and other factors on longer term changes in well-being.
In addition to acting as an outcome measure QoL measures could be helpful within the clinical setting as an indicator of clinical need and assist the clinician in identifying areas of life that are particularly difficult for a child in order that appropriate support can be engaged. ADHD impacts on many aspects of life and although clinicians now have much more information regarding the best ways to reduce ADHD symptoms it is also important for us to always be alert to the associated difficulties faced by these children and to consider how best we can improve their lives.
In summary, published studies to a degree support an impact of ADHD on QoL, which is at least as great as seen for many physical disorders. These effects are greatest, and most consistent, with parent ratings than child-self ratings. Future research needs to distinguish QoL effects from those related only to symptoms and functional impairment; study the differences between child and parent perceptions of ADHD and its impact; identify common elements across the multiple measures currently in use; use population as well clinical samples; include independent ratings of QoL and ADHD symptoms; study the effects of a broader range of treatments in a way that allows the assessment of mediating and moderating factors.