Discussion and limitations
Without exception, all plausible scenarios for England and Germany point to a further increase of expenditures for ADHD medication. The striking extent of the projected increase may appear counterintuitive, but it is easily explained by the simultaneous and multiplicative effects exerted by four variables, i.e., increases in diagnosis prevalence, treatment prevalence, treatment intensity, and the shift to more expensive new products. Over a wide range of assumptions, all projections concur indicating a strong impact of this increase on the individual drug budgets of physicians treating patients with ADHD.
Some important limitations of the present analysis warrant discussion. First, the present analysis does not purport to convey value judgments. It has little to nothing to say about the clinical appropriateness of the prescriptions analyzed; its mere focus is on their budgetary impact.
Second, there is substantial uncertainty around future events. Compounds in development may be discontinued, marketed drugs may be withdrawn because of serious adverse events, safety concerns may slow down diffusion of new products, and so on. The dynamic health policy environment is yet another factor. However, it would hardly be a prudent response to uncertainty to abandon planning and taking a proactive role in the pursuit of efficient service provision.
In strategic management, scenario analysis is a well-established tool to deal with environmental uncertainty [65]. The practice of scenario planning implicitly acknowledges that "best guesses" of future events may be wrong. Therefore, any scenario should not be confused with a forecast of the future. Multiple scenarios are pen-pictures of a range of plausible futures (Figures 3 and 4). Though each individual scenario has an infinitesimal probability of actual occurrence, combined a range of scenarios can shed light on possible future outcomes. This in turn should enable to plan for the range of futures that could, plausibly, unfold.
A third important limitation of this study concerns its restricted scope. Although pharmaceutical spending is likely to rise faster than other ADHD-related expenditures, it is certainly not the only cost component to be considered in a complete budgetary impact analysis [30,66]. Even more importantly, cost analyses illuminate just one half of the health economic equation; they do not provide information on "value for money", frequently analyzed in terms of cost-effectiveness [67]. Cost-effectiveness analyses of ADHD treatment strategies, however, have been rare [68], are only now beginning to appear [69-71], and have generally been limited to a one-year time horizon [72].