Dorien Bangma

204 | CHAPTER 8 the influence of these medication in current results is probably negligible. The use of other types of medications was not sufficiently studied in current study. Another limitation is that the total administration time of the questionnaires was longer than initially expected. On average, participants needed 56 minutes to complete all questionnaires. The sequence of questionnaires was, however, equal for all participants (see Materials and Methods). Nevertheless, especially for individuals with attentional problems, this duration may have been of influence on the pattern of answers on the questionnaires. Participants were able to pause the program and complete the questionnaires at a later point in time, which on the one hand might have reduced the effects of inattention and fatigue, but, on the other hand, also contributed to the relatively long administration time of the questionnaires. In this respect, it is interesting that the ADHD groups did not differ in the average administration time ( F (3,506) = .33; p = .808). A third limitation is that the use of different recruitment and compensation modalities might have resulted in differences in clinical or demographical characteristics and motivation between participants recruited via an online research panel (n = 474) and participants recruited via other modalities (n = 818). Additional analyses comparing participants recruited via these two modalities, however, indicated no significant differences between groups with regard to retrospective and current symptoms of ADHD. Furthermore, no marked differences in the main findings were found between these modalities (data not published). Another limitation is that no direct causal conclusions can be drawn about the observed associations between the dependent and independent variables in current study. This is a common problem in cross-sectional studies and especially when studying personality and psychopathology (Trull, 2011; Widiger, 2011). In the current study, it is conceivable that there is an overlap in the studied constructs of personality, impulsive buying and decision styles, that these constructs simultaneously influence each other or that these constructs share an underlying etiology (Widiger, 2011). Prospective longitudinal research is, therefore, recommended to further investigate the causality between personality and financial decision styles and impulsive buying. A final limitation is that the use of a conservative alpha level for the regression analyses reduced the risk of type 1 errors but increased the possibility of type 2 errors. Furthermore, the use of a large sample with a relatively small percentage of individuals with symptoms of ADHD or individuals meeting the self-reported symptom criteria of adult ADHD in the regression analyses, may have contributed to potential type 2 errors. All relations found in the present study were, however, mostly weak which indicates a low likelihood of type 2 errors. Furthermore, additional regression analyses using only participants from the four ADHD groups (n = 529; data not published) showed again no significant association between financial decision-making and symptoms of ADHD, while results with regard to the relation with demographic variables, personality or symptoms of depression were comparable to the original analyses. Conclusion. Despite the described limitations, the results of the present study appear to confirm previous research in adults with ADHD and indicate more impulsive buying and more frequent use of disadvantageous financial decisions styles (i.e., avoidant and spontaneous styles) in individuals fulfilling self-reported current ADHD criteria (i.e., individuals with