Entrepreneurship & Attention Deficit/Hyperactivity Disorder: A Large-Scale Study Involving the Clinical Condition of Adhd

A growing conversation has emerged linking ostensibly dark or pathological individual-level characteristics to entrepreneurship. Attention Deficit/Hyperactivity Disorder (ADHD) emerged as a proof-of-concept phenomenon. Recent studies in entrepreneurship journals have made great strides – articulating the theoretical relevance of ADHD-type behavior in entrepreneurship, and suggesting a positive link consistent with narratives in the popular press. While the recent research has made important inroads, quantitative studies have yet to empirically examine ADHD in line with its theoretical roots and definition – as a full-blown clinical disorder. The present paper contributes by providing a theoretically-empirically aligned test of the connection between clinical ADHD and entrepreneurial intention as well as action.


INTRODUCTION
By the end of the 20 th century, the entrepreneurship literature had built a body of knowledge on logical, generally positive, factors associated with business venturing such as human capital, financial capital, cognitive biases, traditional traits differentiating entrepreneurs (Shane, 2003). Building on that tradition, in the present 21 st century, scholars have made great strides in advancing entrepreneurship theory -covering many other factors associated with venturing such as regulatory-focus (Tumasjan & Braun, 2012;Hmieleski & Baron, 2008), affect and passion (Baron et al., 2012;Cardon et al., 2012;Gielnik et al., 2017). Recently, a relatively new and growing conversation has emerged -that involving conventionally dark or pathologized constructs that may be positively associated with entrepreneurship. Among the most prominent, and previously suggested in the popular press (Archer, 2014;The Economist, 2012), is Attention Deficit/Hyperactivity Disorder (ADHD). Characterized by behavioral disinhibition, ADHD is indicated by impulsivity, hyperactivity, and problems with attentional regulation (APA, 2013).
The theoretical and practical relevance of the above to entrepreneurship has recently been discussed (Verheul et al., 2015;2016;Thurik et al., 2016;Wiklund et al., 2016a;2016b;2017;Miller & Le Brenton-Miller, 2016;Lerner, 2016;Antshel, 2017;Canits et al., 2018). In particular, a number of studies drawing on the ADHD literature have emerged, suggesting a positive association between ADHD related behavior and entrepreneurship, including an increased likelihood of entrepreneurial intentions (Verheul et al., 2015;Canits et al., 2018), venturing  and orientation . These and related studies provide an important point of departure for the present investigation. In essence they deal with behavioral tendencies that at the high-end of the spectrum might be indicative of ADHD or other (possibly comorbid) disorders. With limited exception (discussed later), recent empirical research, while grounded in the clinical literature of Attention Deficit/Hyperactivity Disorder, has yet to empirically examine actual ADHD -a diagnosed clinical disorder. In other words, while predicated on prior research on the clinical condition of ADHD, the emerging link with entrepreneurship has yet to examine whether actual ADHD is significantly linked to a higher propensity for entrepreneurial intention and action. We contribute to recent theory about a positive ADHD--entrepreneurship link by providing a simple theoretically-empirically aligned test of the connection between actual ADHD and entrepreneurship.
The present work offers a number of contributions. It generally foments the emergent scholarly interest in the link between mental conditions and entrepreneurship (Hatak et al., 2016;2017;Wiklund et al., 2017) -by focusing on a common condition that affects hundreds of millions of adults world-wide (de Graaf et al., 2008), and that may be over-represented in entrepreneurial environments. Specifically, we go beyond recent research relating ADHD-related behavior to entrepreneurship (Lerner, 2016;Verheul et al., 2015;2016;Thurik et al., 2016;Wiklund et al., 2016b;Canits et al., 2018). Based on the reported large-scale study involving actual ADHD, we directly test whether ADHD is linked to an increased propensity for both entrepreneurial intention and action. In conjunction with related entrepreneurship research, this offers a novel basis for entrepreneurship theory, future research, and practice.

Attention Deficit/Hyperactivity Disorder -The Condition
Attention Deficit/Hyperactivity Disorder is a common clinical condition, defined by impulsive, hyperactive, and inattentive behavior (APA, 2013), affecting individuals of all ages worldwide. With a full discussion of clinical diagnostic criteria beyond the scope of this paper, for ADHD to exist, the impulsive, hyperactive, and inattentive behavior must be pervasive, enduring, and -to an age inappropriate frequency and magnitude -materially impairing normal functioning (APA, 2013). Adult ADHD is well established in scientific literature (Barkley et al., 2008;Kessler et al., 2005;2007) and is known to affect organizations and vocational behavior (Bozionelos and Bozionelos, 2013;de Graaf et al., 2008;Halbesleben et al., 2013;Kessler et al., 2009).
Like other disorders, ADHD is diagnosed by a licensed clinician (e.g. a clinical psychologist or psychiatrist), based on a battery of psychological tests and other data. It also requires differential diagnosis, meaning that the clinician must judge that the behavior and impairment consistent with ADHD is not attributable to another cause (e.g. mania, substance abuse, or say distractibility and impulsivity caused by a lack of sleep or being in the midst of a difficult divorce). Suffice to say, there is no single test, let alone any simple psychometric measure, able to determine if an individual has ADHD. ADHD is, by definition, a clinical construct and disorder that has its roots in the extensive clinical literature, which over the past 30 years has established the validity condition (APA, 2013;Goldman et al., 1998) and the vast majority of its effects. Consistent with traditional clinical psychology and psychiatry, in the clinical literature ADHD is considered inherently pathological.

ADHD in Organizational Scholarship
In terms of the emerging management and entrepreneurship literature involving ADHD, recent studies have relaxed the need to empirically consider actual ADHD (i.e., individuals with the condition) and instead have taken a disposition-type approach (with two exceptions subsequently elaborated). There are good and pragmatic reasons for this. The non-clinical consideration of a clinical construct has allowed empirically tractable investigations and uncovered significant, non-obvious findings -namely the positive association between ADHDtype behavior and entrepreneurship.
There are two noteworthy exceptions. First, the recent study of Wiklund, Patzelt, and Dimov (2016) illustrates and provides insight into how 14 Swedish entrepreneurs with ADHD 'behave'. Their work demonstrates the entrepreneurial relevance of having ADHD. In line with its qualitative design and contribution, the study cannot speak to -but rather further motivatesthe need to understand whether there is a significant positive connection between ADHD and entrepreneurship (whether ADHD significantly increases the likelihood of venturing). The second partial exception comes from Verheul et al. (2016) study linking individuals' continuous scores on an ADHD screener (the ASRS v1.1) to their self-employment status in two datasets.
Specifically, Verheul et al. (2016) performed a sensitivity analysis where individuals were screened as positive or negative for ADHD based on their ASRS score. Linking the dichotomous (positive vs. negative) screening variable to self-employment, the authors find that the positive association between ADHD (type behavior) and self-employment holds.
For organizational research involving ADHD to advance, however, there is an issue. While empirically not studying actual ADHD, the extant entrepreneurship research imported ADHD from the clinical literature, including a short screening tool 1 for identifying individuals for possible clinical referral/evaluation. We appreciate that this can be entirely appropriate, depending on the research question, the state of (incipient) knowledge, and research constraints.
The present concern and hitherto limitation is the absence of a large-scale basis to consider whether the reported connection with entrepreneurship is true if considering actual Attention Deficit/Hyperactivity Disorder. Thus, the unresolved issue with the extant theory and research, suggesting a positive ADHD-entrepreneurship link, is that it has been built on, and is fundamentally grounded in, the clinical literature (applying a clinical construct and using a screening tool) -without yet comparing individuals with and without the condition of ADHD.
Toward building a sound literature, we need to understand if the recently suggested positive connection between ADHD and entrepreneurship is veridical in the sense that this relationship holds when using the strict definition of ADHD -i.e., operationalizing it dichotomously as the diagnosed conditioned it fundamentally is. Based on the empirical and theoretical origins of ADHD, finding a positive link between the diagnosed condition and entrepreneurship would substantially bolster the emerging conversation. Specifically, this would validate recent entrepreneurship theory and findings that, although they involve clinical literature, yet have not empirically treated and linked Attention Deficit/Hyperactivity Disorder to entrepreneurship. Thus, extending recent research that has examined a behavioral disposition that at one end of the spectrum might be indicative of ADHD (Lerner, 2016;Thurik et al., 2016;Verheul et al., 2015;2016;Wiklund et al., 2016b), true to the grounding literature and ADHD construct, we focus on the actual condition of ADHD.

ADHD and Entrepreneurial Intention
Notwithstanding a greater ultimate interest in entrepreneurial action (versus intention), an important starting point for the scholarly consideration of a connection between ADHD and entrepreneurship is provided by Verheul et al. (2015). It is the first large-scale scientific inquiry focusing on the topic. Sampling of over 13,000 university students, Verheul et al. (2015) link a continuous indicator of ADHD-like behavior to entrepreneurial career intentions. 2 We begin by first asking if the apparent ADHD -entrepreneurial intentions link indeed exists when considering the actual clinical condition. It is hitherto unclear whether, within a normal professional-oriented adult population, those who actually have ADHD show significantly higher entrepreneurial intentions than those without this condition. Potentially validating and extending prior research, we will empirically explore whether: (1) Individuals with actual ADHD have higher entrepreneurial intentions than those without.

ADHD and Venturing/Entrepreneurial Action
Individual entrepreneurial action is central to entrepreneurship; without such "there would simply be no entrepreneurship and no new ventures" (Baron, 2007: 167). Considering ADHD as a clinical condition affecting individual behavior, we acknowledge that it could have opposing effects on one's propensity to undertake entrepreneurial action. Although entrepreneurship is generally perceived to involve risky, complex and innovative activities (something typically attractive to individuals with ADHD), the reality of starting a business may be far less exciting or motivating. In particular, starting a firm involves many tasks that are formal, protracted, administrative, and require attention to mundane detail. Individuals with ADHD tend to struggle with such activities, and also perceive them as less attractive (Barkley, 1997). Thus, when it comes to starting a venture and associated activities requiring sustained attention to details, individuals with ADHD may be apt to procrastinate such action or be otherwise distracted by more stimulating activities (including thinking about other opportunities/venture ideas).
Following this line of reasoning, the classical pathological perspective on ADHD would suggest that individuals with ADHD may be significantly less likely to venture, compared to individuals without ADHD.
Alternatively, considering that entrepreneurship requires an action orientation (Frese, 2009;Sarasvathy, 2001) and given that unfettered even impulsive action is central to ADHD (APA, 2013), the opposite might be true. In individuals with ADHD "act first, think later" behavior prevails, meaning action itself is often prepotent (i.e. will be expressed in the absence of topdown restraint) (Barkley, 1997). This suggests that, at least for experimenting with entrepreneurship, those with ADHD may very well act without much or any forethought or consideration of potential consequences. In this respect, ADHD's disinhibition (Barkley, 1997;Lerner, 2016) promotes action. Consistent with this, Wiklund et al. (2016a) document considerable entrepreneurial activity in their study of 14 ADHD-entrepreneurs. Likewise, in their sensitivity analysis, Verheul et al. (2016) find a positive link between a dichotomized score on the ASRS v1.1 screener and self-employment. Though the latter can be considered stricter than using continuous ASRS scores, ADHD diagnostic status was entirely unknown. Additionally, a positive dichotomous score does not mean an individual has ADHD, rather that further evaluation by a clinician might be appropriate. Hence, neither the recent extant studies nor the extensive popular press provide conclusive empirical evidence of the central question whether ADHD significantly increases (or decreases) the probably of venturing/entrepreneurial action.
Appreciating the ambivalent nature of ADHD, we note that early-stage venturing primarily involves initiating entrepreneurial action. Consequently, we offer but at the same time question the notion that individuals with ADHD -a clinical disorder -are more likely than others to venture. We will empirically examine whether: (2) Individuals with ADHD are more likely to venture/engage in entrepreneurial action, than those without.

METHOD
To examine whether the positive ADHD -entrepreneurship connection suggested by recent studies is in fact true when taking into account the actual disorder, a large-scale study was undertaken. The purpose was to provide a basic straightforward examination of the connection between the condition of ADHD (independent variable) and entrepreneurial intention (dependent variable 1) as well as nascent venturing (dependent variable 2).
As such, we were not interested in full-time entrepreneurs or employees -but rather focus on a population that is heterogeneous in terms of venturing activity (distinguishing between nascent actors and non-actors) as well as career intentions (distinguishing between individuals with and without intentions). Accordingly, and following Verheul et al. (2015), we sampled about 9,800 university students who participated in GUESSS Netherlands 2014. Comparing the Dutch sample with the global GUESSS sample, reported in Sieger et al. (2014), our sample was representative in terms of age, gender, management students, and the prevalence of selfemployed parents 3 .
In relation to the research question, this sample is not intended to proxy some other population such as entrepreneurs, and offers a number of advantages. Given the nature of the sample and age of the respondents, the inquiry offers the advantage of capturing individuals prior to the possibility of being forced into entrepreneurship, and prior to selection and sampling biases that would be present in older workers. On a related note, it is important to acknowledge that individuals with ADHD are less likely to attend university and may be pushed into Entrepreneurial Intentions -based on Linan and Chen (2009) and for robustness and replication, also operationalized dichotomously with post-secondary career intention (Verheul et al., 2015); 3) Venturing/Entrepreneurial Action -operationalized as whether the individual was in the process of starting or already running a venture; 4) Control variables -gender, age, selfemployed parents, academic performance, management as field of study. These controls were included based on their consistency with prior entrepreneurship research. Considering the sample, the latter two adjust for the potential effects of academic performance or area of study.
In terms of ADHD, 4.2% reported having the diagnosed condition 4 . This is comparable to the adult ADHD community prevalence rate of 5% in the Netherlands (de Graaf, et al., 2008) and more broadly to the 3.4% across 10 countries according to World Health Organization studies (de Graaf, et al., 2008). That said, the following issues may arise when collecting the data. First, there is the possibility of under-reporting: some individuals with ADHD might falsely report that they do not have the condition, for example because they fear stigmatization.
Such false-negatives would reduce an already very minority base-rate and add noise to the 4 ADHD is associated with genetics and stable neurological differences (physical brain-structure and neurotransmitters). Individuals previously diagnosed that may no longer meet diagnostic criteria, whether per taking medication or for other reasons, are often considered in-remission. In relation to the current research, bifurcation between ADHD diagnosed individuals currently meeting diagnostic criteria and those who could be clinically considered in-remission, it is neither realistic (as it would require individual clinical evaluations by psychiatrists or clinical psychologists) nor is it essential for our basic research question. empirical testing -increasing the likelihood null-effects (and Type-II error), and decreasing the likelihood of significant results. Second, in terms of possible over-reporting, there was no reason for undiagnosed individuals to falsely report an ADHD diagnosis in the data collection. Also, the rate of 4.2% does not suggest an over-reporting problem. Third, undiagnosed individuals who would qualify for a diagnosis do not lead to spurious positive results but rather would make any true positive effect more difficult to detect. Finally, it is possible that some of the diagnosed individuals take ADHD medication (or may be considered "in remission" by a clinical psychologist/psychiatrist); however the implications of such are beyond the scope of our central research question. Furthermore, as not bifurcating diagnosed individuals taking ADHD medication from those not taking medication would not result in spurious results -and with the recent studies cited also not controlling for possible use of medication -we do not complicate our study by including medication. In summary, considering the above, any significant findings would likely be conservative in nature.

RESULTS
The following are the results of the large-scale empirical inquiry conducted. Table 1 presents the descriptive statistics and correlations. Table 1 here >> Tables 2 and 3 present the results of the standard regression analyses. We find that a reported ADHD diagnosis positively predicts entrepreneurial intentions. This was the case whether operationalized as a continuous variable, following Linan and Chen (2009), or as a dichotomous variable, following Verheul et al. (2015). In terms of the readily interpretable latter measure, individuals with ADHD were approximately 1.7 times (60-80%) more likely to have entrepreneurial intentions (Models 1c and 1d in Table 2). This extends the findings of Verheul et al. (2015), assuaging the clinical-but-non-clinical disjuncture of prior research, and validating the veridicality of the previously suggested positive link with intentions. Table 2 here >> More importantly, an ADHD diagnosis positively predicts entrepreneurial action. In particular, having actual ADHD increases the odds of venturing by almost 100%. The results indicate that university enrolled adults with ADHD are almost two times more likely to initiate entrepreneurial action than those without ADHD (Models 2a and 2b in Table 3). In other words, among individuals who still have to make a vocational choice and have no need to venture, those with the disorder of ADHD were not less or similarly likely to venture than those without the disorder -but rather were significantly more likely to venture. Considering that individuals with ADHD are less likely to attend post-secondary education and more likely to struggle with conventional employment, these results may understate the true effect size relative to the overall population. Considering the design and nature of the sample, these results do not speak to venturing outcomes. Simply, the results provide a straightforward test and clear support for a positive link between ADHD and entrepreneurship, attributable to individual choice versus a vocation of last resort. Table 3 here >> These results extend prior research and establish a potential upside or non-pathological effect of a clinical disorder. Given the research question, the highly significant positive effect of ADHD and the associated odds-ratios -indicative of a large effect -are the focus. This low total variance explained rightfully indicates that there are myriad factors influencing whether an individual is interested and will engage in venturing. Moreover, given the representative but minority frequency of individuals with ADHD diagnoses in the sample, the overwhelming majority of the sample is non-ADHD and, accordingly, low R 2 s are not just normal but mathematically ought to be observed. 5 If around 4% of a sample has some dichotomous condition, and many individuals without the disorder also venture, looking at R 2 is analogous to say looking how much of the total probability of engaging in Corporate Acquisition activity is explained by a relatively uncommon predictor such as CEO ADHD. However, the objective and research question is not about explaining the broad preponderance of the dependent variable, but instead is about understanding whether a theoretically meaningful, yet relatively low-base rate, predictor indeed has a significant and material effect on the probability of nascent venturing. As such, the highly significant readily interpretable odds-ratios, indicative of a large effect are informative and meaningful. The results indicate that not only is the effect of ADHD statistically significant, but that it very materially increases the odds of venturing (increases the likelihood by almost 100%, 79% after controls)which is at least as much as other well-established predictors such as having entrepreneur parents (Model 2b).

DISCUSSION
The present paper extends recent entrepreneurship research, using a stricter conceptualization and measurement of ADHD -that is, actual ADHD, a clinically diagnosed condition. The results find that, in spite of ADHD's downsides and individuals having sufficient disorder as to be clinically diagnosed, it positively rather than negatively affects the likelihood of venturing. Building on prior research, this elucidates that a dark and pathologized condition can serve as a wellspring for entrepreneurial action.
This complements the qualitative findings of Wiklund et al. (2016a) and Verheul et al.'s (2016) quantitative findings based on dichotomized ASRS v1.1 scoring. Based on our large-scale quantitative testing that did not preselect on either ADHD status or observable entrepreneurs, and prior to choosing entrepreneurship as last resort, we find evidence that individuals with diagnosed ADHD are significantly more likely to take entrepreneurial action than individuals without such a diagnosis. It suggests the potential adaptiveness of the unequivocally pathological -going beyond a behavioral trait such as impulsivity to a full-blown clinical disorder/diagnosis.
Our findings empirically advance emergent theory, characterized well by Wiklund et al. (2017) with the telling title "Mental disorders in the entrepreneurship context: When being different can be an advantage." Concurrently, it is important to underscore that entrepreneurial action and performance are far from synonymous. The linkage found between ADHD and nascent venturing should absolutely not be conflated or interpreted to suggest a positive link with business venture performance. The reported study cannot speak to the effect of ADHD on venture performance.
Rather, it suggests the need and opportunity for future research in this direction. Certainly, in the face of the idea that managerial tasks increase when ventures grow and performance becomes an issue, and that the links between managerial tasks and ADHD are not obvious. Thus, the link between ADHD and performance merits future investigation.
Additionally, it is also important to note some limitations. The simple, straightforward design and sample used were appropriate for the critical research question of whether in fact actual ADHD and the likelihood of entrepreneurial action are connected. The resultant coefficient estimates, while likely conservative in nature for aforementioned reasons, should however not be presumed to be broadly generalizable to other populations (Antshel, 2017;Canits et al, 2018). Generalizability to other populations may be a question of how large the effect is.
Finally, at an even deeper level, it is important to recall that generalizability is not per say a property of any empirical study, but rather is a question of whether a theoretical relationship generalizes across empirical contexts (Zelditch, 1969). As our findings quite strongly ground prior research and establish the central theorized relationship, they indicate the fruitfulness of future research involving other populations, other designs, and more complex theory.
The present work foments and contributes to various scholarly conversations, particularly those involving mental health or ADHD and entrepreneurship (Hatak et al., 2016;2017;Lerner, 2016;Thurik et al., 2016;Verheul et al., 2015;2016;Wiklund et al., 2016a;2016b;Canits et al., 2018). It also serves as a basis for future research. For example, the finding that individuals with ADHD are almost two times as likely to venture, indicates the importance of further studies on ADHD and venturing outcomes. This is particularly so once considering the otherwise squandered human capital, the costs of business failure, and/or the many adverse outcomes associated with unchanneled adult ADHD (such as absenteeism, unemployment, substance abuse, incarceration).
Bolstered by the findings of our large-scale quantitative inquiry, ADHD has implications for organizational research, practice and policy. Research implications include highlighting the need for further study of contextual factors determining under which conditions ADHD is a strength or a weakness, and is adaptive or counter-productive in venturing. In regards practice and policy, understanding that mental health, and ADHD in particular, has dark and bright sides for entrepreneurship, has various implications. For example, it suggests the opportunity for research to help educators, clinicians, and even organizations focus on strengths (such as a willingness to act, an imperturbable focus on activities of interest) and compensate for weaknesses (such as distractibility and poor attention to detail in mundane activities). More generally, it suggests the continued opportunity for considering other predictors potentially seen as aberrant in respect to entrepreneurship (Hatak et al., 2016;Hmieleski & Lerner, 2016;Wiklund et al., 2017).
Overall, the present work contributes to theory by grounding recent research positively linking ADHD and entrepreneurship -with a large-scale quantitative examination that squarely tests the effect of (actual) ADHD. In concert with other studies, the work establishes an emergent entrepreneurship literature on ADHD. In doing so, it attests to broader emerging theory that generally suggests the relevance of clinical or otherwise dark constructs in entrepreneurship.  Significant at: †=0.10, *=0.05, **=0.01, ***=0.001, 2-tailed.
Note: Differences in reported Ns are per missing data from some subjects (SPSS pairwise exclusion).