The association between attention-deficit/hyperactivity (ADHD) symptoms and self-employment

Abstract

Attention-deficit/hyperactivity (ADHD) symptoms have been associated with the decision to become self-employed. Although these symptoms are generally regarded as disadvantageous, there may also be a bright side. To our knowledge, however, there has been no systematic, epidemiological evidence to support this claim. This paper examines the association between ADHD symptoms and self-employment in a population-based sample from the STAGE cohort of the Swedish Twin Registry (N = 7208). For replication, we used a sample of Dutch students who participated in the Global University Entrepreneurial Spirit Students' Survey (N = 13,112). In the Swedish sample, we found a positive association with self-employment for both general ADHD symptoms [odds ratio (OR) 1.13; 95 % confidence intervals (CI) 1.04-1.23] and hyperactivity symptoms [OR 1.19; 95 % CI 1.08-1.32], whereas no association was found for attention-deficit symptoms [OR 0.99; 95 % CI 0.89-1.10]. The positive association between hyperactivity and self-employment was replicated in the Dutch student sample [OR 1.09; 95 % CI 1.03-1.15]. Our results show that certain aspects of ADHD, in particular hyperactivity, can have a bright side, as they are positively associated with self-employment.

Full text

BEHAVIOURAL EPIDEMIOLOGY
The association between attention-deficit/hyperactivity (ADHD)
symptoms and self-employment
Ingrid Verheul
1,5
•Wim Rietdijk
2,3
•Joern Block
4,5
•Ingmar Franken
6
•
Henrik Larsson
8,9
•Roy Thurik
2,3,5,7
Received: 24 February 2015 / Accepted: 4 May 2016 / Published online: 13 May 2016
ÓThe Author(s) 2016. This article is published with open access at Springerlink.com
Abstract Attention-deficit/hyperactivity (ADHD) symp-
toms have been associated with the decision to become
self-employed. Although these symptoms are generally
regarded as disadvantageous, there may also be a bright
side. To our knowledge, however, there has been no sys-
tematic, epidemiological evidence to support this claim.
This paper examines the association between ADHD
symptoms and self-employment in a population-based
sample from the STAGE cohort of the Swedish Twin
Registry (N =7208). For replication, we used a sample of
Dutch students who participated in the Global University
Entrepreneurial Spirit Students’ Survey (N =13,112). In
the Swedish sample, we found a positive association with
self-employment for both general ADHD symptoms [odds
ratio (OR) 1.13; 95 % confidence intervals (CI) 1.04–1.23]
and hyperactivity symptoms [OR 1.19; 95 % CI
1.08–1.32], whereas no association was found for atten-
tion-deficit symptoms [OR 0.99; 95 % CI 0.89–1.10]. The
positive association between hyperactivity and self-em-
ployment was replicated in the Dutch student sample [OR
1.09; 95 % CI 1.03–1.15]. Our results show that certain
aspects of ADHD, in particular hyperactivity, can have a
bright side, as they are positively associated with self-
employment.
Keywords Attention-deficit Hyperactivity Symptoms 
ADHD Self-employment
Introduction
Prominent entrepreneurs have publicly credited their
attention-deficit hyperactivity (ADHD) symptoms as a
driver of their decision to become self-employed [1–3].
Examples include Ingvar Kamprad (founder of IKEA) and
Richard Branson (founder of the Virgin Group) [2,3]. The
Economist recently published a short article addressing the
suitability of self-employment for people who experience
ADHD symptoms [4].
ADHD is a neurodevelopmental disorder characterised
by attention-deficit and hyperactivity [5–7]. The onset of
ADHD is typically during childhood (before the age of 12),
and it is therefore often regarded as a childhood disorder.
Studies following children with a diagnosis of ADHD have
shown that ADHD symptoms are persistent over time, at
least into early adulthood [6,8–11], with 65 % of indi-
viduals still having a full ADHD diagnosis or partial
remission at the age of 25 [12]. Recent research has
&Ingrid Verheul
iverheul@rsm.nl
1
Rotterdam School of Management, Erasmus University
Rotterdam, P.O. Box 1738, 3000 DR Rotterdam,
The Netherlands
2
Erasmus School of Economics, Erasmus University
Rotterdam, Rotterdam, The Netherlands
3
Institute for Behavior and Biology (EURIBEB), Erasmus
University Rotterdam, Rotterdam, The Netherlands
4
Professur fu
¨r Unternehmensfu
¨hrung, Universita
¨t Trier, Trier,
Germany
5
Erasmus Research Institute of Management (ERIM), Erasmus
University Rotterdam, Rotterdam, The Netherlands
6
Institute of Psychology, Erasmus University Rotterdam,
Rotterdam, The Netherlands
7
Montpellier Business School, Montpellier, France
8
Department of Medical Epidemiology and Biostatistics,
Karolinska Institutet, Stockholm, Sweden
9
Karolinska Institutet Center of Neurodevelopmental
Disorders (KIND), Stockholm, Sweden
123
Eur J Epidemiol (2016) 31:793–801
DOI 10.1007/s10654-016-0159-1
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devoted more attention to increasing our understanding of
the persistence of ADHD symptoms in (young) adults [13].
Furthermore, the most recent DSM criteria were adjusted to
enable a diagnosis across the lifespan and not only during
childhood [14].
Although prior research has mainly focused on the
negative consequences of ADHD for individual perfor-
mance in formal education and wage employment [15–19],
recent studies have highlighted positive aspects of ADHD
symptoms, such as its association with resilience and well-
being [20], close friendship [21], and third-party inferences
about an individual’s generative qualities (being creative,
visionary, good at generating ideas) [22]. In the present
study, we focus on a potential positive aspect of ADHD:
self-employment as a career choice. Self-employment is
not just any career choice but is a manifestation of
entrepreneurship that is essential for employment creation,
innovation and the economic growth of modern societies
[23,24]. It can be used as an economic instrument in the
business cycle [25] and to lift people out of unemployment
[26].
In the popular press, it has been suggested that indi-
viduals with ADHD symptoms are able to break through
organisational inertia due to their ability to envision and
create new ‘realities’ and (successfully) start their own
ventures [2–4]. Allegedly, when individuals who experi-
ence ADHD symptoms succeed in developing mechanisms
to cope with their ‘weaknesses’, they would be able to
exploit their extraordinary talents and perform just as well
as or even better than their peers in business [2,27,28].
Academic research has found only circumstantial evidence
linking ADHD symptoms to self-employment when
examining the association with entrepreneurial intentions
[29], creativity [30–32], risk-taking [33], and proactivity
[5]. To our knowledge, there is no systematic, epidemio-
logical evidence supporting a link between ADHD symp-
toms and self-employment.
The present study was designed to examine the associa-
tion between self-reported ADHD symptoms and self-em-
ployment in a population-based sample of 7208 individuals
from the STAGE cohort of the Swedish Twin Registry of the
Karolinska Institute. The findings were replicated in a
sample of 13,119 students participating in the Global
University Entrepreneurial Spirit Students’ Survey
(GUESSS) 2011 in the Netherlands. Given the discussions
in the (popular) literature and the circumstantial scholarly
evidence, we expected a positive association between
ADHD symptoms and the decision to become self-em-
ployed [1–4,29]. We should emphasise that the present
study does not focus on ADHD as a full-blown psychiatric
disorder. For the purpose of the present research, self-re-
ported psychiatric symptoms are defined along a continuum
[34] and not as a psychiatric classification.
Method
Swedish twin registry: STAGE cohort
as the discovery sample
We used the STAGE (Swedish Twin Studies on Adults:
Genes and Environment) cohort from the Karolinska
Institute in Stockholm, Sweden, as the discovery sample.
The STAGE cohort is part of the population-representative
Swedish Twin Registry (STR), which was established in
the 1950s to study the effects of smoking and drinking on
cancer and cardiovascular diseases [35]. At present, the
STR contains rich data about biological and clinical
markers together with the socio-economic background of
twins living in Sweden [35]. For a full account of the
design and execution of the STR project and details of the
ADHD data in the STAGE cohort, we refer to Lichtenstein
et al. [35] and Larsson et al. [10], respectively.
All twins born between 1959 and 1985 (a total of 42,582
twins) received an invitation letter with information about
the project in May and June 2005. The response rate was
59.6 % (N =25,364, 56 % female, age[mean] =41.56,
age[sd] =7.6). The entire questionnaire contained
approximately 1300 questions, of which the respondents
answered 800–900 questions on average [35]. Dropouts
could be explained by a general unwillingness to respond
to a lengthy survey [10]. Non-respondents were signifi-
cantly more often male, had at least one parent born outside
Sweden, and were more likely to have been diagnosed with
a psychiatric disorder and convicted of any type of crime
[10,36,37], which may indicate that the most severe cases
did not respond to the questionnaire. This limits generali-
sations to the more severe cases of the ADHD spectrum.
Informed consent was obtained from all individual partic-
ipants included in the study. This project was reviewed and
approved by the ethics committee of the Karolinska
Institute.
Self-employment measure
Participants answered two questions about their involve-
ment in self-employment: whether they were self-em-
ployed full-time (yes/no) and whether they were self-
employed part-time (yes/no). We constructed one measure
of self-employment (yes/no), which was coded 1 if the
participant was self-employed part-time or full-time and 0
if (s)he was not self-employed. In the STAGE cohort,
14,039 out of 25,364 participants (&55 %) provided their
self-employed status (yes/no). A total of 2096 participants
(&14 %) were self-employed, of whom 1270 (&9%)
were self-employed full-time and 826 (5 %) were self-
employed part-time. Three participants answered ‘yes’ to
both the part-time and full-time self-employment question
794 I. Verheul et al.
123
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and were excluded from the analysis. Furthermore, we
randomly dropped one twin from each pair because their
similarity would violate the assumption of independent
observations, resulting in a final sample of 7208 partici-
pants (58 % female, age[mean] =43.9, age[sd] =6.7). Of
these respondents, a total of 897 (&12 %) were self-em-
ployed, of whom 515 (&7 %) were self-employed full-
time and 382 (&5 %) were self-employed part-time, which
was similar to the total sample distribution.
Attention-deficit/hyperactivity (ADHD) symptoms
measure
ADHD symptoms were assessed using the Adult ADHD
Self-Report Scale (ASRS-v1.1), which consists of 18 items
reflecting the DSM-IV-TR criteria [10]. Attention-deficit
symptoms and hyperactive symptoms were measured by 9
items each.
1
Answers for each item were given on a 3-point
Likert scale (0 =‘no’; 1 =‘yes, to some extent’; and
2=‘yes’). The 18 ASRS-v1.1 items were slightly modified
to allow for the assessment of ADHD symptoms in adults
[35]. As can be expected from a non-clinical population
sample, many participants reported having no or few ADHD
symptoms. The average percentage of respondents reporting
inattentive symptoms and hyperactive symptoms (with the
answer ‘yes’) was 3.6 and 4.6 %, respectively. Approxi-
mately one-third of the respondents reported no symptoms
[10]. This result closely resembles the prevalence rate of
adult ADHD reported in Kessler et al. [38].
The symptom scores were added to create a scale of
ADHD symptoms and two sub-scales of attention-deficit
and hyperactivity [10]. Values for the reliabilities of these
three scales in our sample were a=0.84, a=0.78, and
a=0.78, respectively. These reliabilities were similar to
those reported in Larsson et al. [10]. Because the three
scales were highly skewed (skewness: ADHD, 1.66;
attention-deficit, 1.77; hyperactivity, 1.72), the scales were
log-transformed (Log10[x ?1], where x is the initial
value) to normalise their distributions (skewness after log
transformation: ADHD, -0.16; attention-deficit, 0.27;
hyperactivity, 0.26). As indicated in Larsson et al. [10,
p. 199], the sum score of the 18 ADHD items used in this
study yielded results similar to those reported in other
studies using self- or parent-reported measures of ADHD.
Control variables
In the STAGE cohort, we included the following demo-
graphic variables: age, gender, and whether the participant
attended university (0 =no, 1 =yes) as an initial test to
control for additional effects.
GUESSS study: replication
We attempted to replicate the analysis linking ADHD
symptoms to self-employment in a student sample from the
Global University Entrepreneurial Spirit Students’ Survey
(GUESSS)
2
2011 in the Netherlands. GUESSS is an
international research consortium that studies the career
objectives of students in higher education. In the Nether-
lands, students at 14 universities and 24 polytechnics
received a link to the online survey through email. After
1 month, a reminder was sent. Two randomly drawn par-
ticipants received an iPad 2.0 to reward their participation.
To prevent self-selection of students with entrepreneurial
intentions, the topic of the survey was announced as future
career paths. The GUESSS Netherlands study was in line
with the Erasmus Research Institute of Management
review board’s standards and did not include clinical or
patient data [29].
The response rate for the GUESSS study was 7.6 % for
educational institutions that systematically recruited par-
ticipants [29], leading to an overall database of 13,119
students (56 % female, age [mean] =22.96, age
[sd] =0.49), of whom 374 were student entrepreneurs
(i.e., reported having their own business during their
studies). Comparing the GUESSS Netherlands sample with
the global GUESSS sample reported in Sieger et al. [39],
we found that our (Dutch) sample was representative in
terms of socio-demographic characteristics and the preva-
lence of student entrepreneurs. Specifically, in our sample,
56 % of the respondents were female compared to a global
average of 55.2 %, and the average age of 23 was within
the mid-range age of the international average, which is
between 20 and 27 years [39]. Furthermore, 2.9 % of the
students in our study had their own company, compared to
a global average of 2.5 % student entrepreneurs [39].
In the GUESSS study, self-employment was measured as
a dichotomous variable indicating whether students were
self-employed in their own founded firm during their studies.
ADHD symptoms were measured using the six-item Adult
ADHD Self-Report Scale v1.1 (ASRS v1.1) screener,
developed by Kessler et al. [38,40], which consists of the six
most predictive ADHD symptoms of the 18 DSM-IV-TR
criteria used in the STAGE study. This enabled us to repli-
cate the analysis in the STAGE cohort. Each item was
answered on a 5-point Likert scale (1 =never to 5 =al-
ways). Although the measures were different, the screener
and the full 18-item measure were found to be highly
1
Throughout the paper we refer to hyperactivity symptoms, although
the ASRS v1.1 measure is slightly broader given that it includes three
items related to impulsivity.
2
For more information about GUESSS, we refer to http://www.
guesssurvey.org.
The association between attention-deficit/hyperactivity (ADHD) symptoms and self-employment 795
123
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correlated [38,40]. Average scores were computed for
ADHD symptoms (based on six items, a=0.59), attention-
deficit (based on four items, a=0.62), and hyperactivity
(based on two items, a=0.43). Although these scales had
low to moderate reliability, they were still close to the lower
bound of reported reliabilities for the ASRS screener ques-
tions in Kessler et al. [40] (see Verheul et al.) [29]. The three
scales were only moderately skewed: sample skewness for
the ADHD symptom scale, the attention-deficit scale, and
the hyperactivity scale amounted to 0.21, 0.35, and 0.06,
respectively, with a standard error of 0.02. These skewness
measures indicated that log-transformation of the variables
was not necessary. Given that the GUESSS study consisted
of only students from universities and polytechnics, we only
included age and gender as control variables in the model.
Statistical analysis
To examine the association between ADHD symptoms and
self-employment, we estimated binary logistic regressions.
First, in the STAGE cohort, we examined the association
between the sum score on the DSM-IV diagnostic criteria
items for all ADHD symptoms (18 items), attention-deficit
and hyperactivity symptoms (each 9 items), and self-em-
ployment (part-time/full-time). Second, we replicated this
analysis using data from the GUESSS study. Specifically, we
estimated the associations between the sum score on the
ASRS-6 v1.1 screener items for all ADHD symptoms (6
items), attention-deficit symptoms (4 items), hyperactivity
symptoms (2 items), and self-employment. We report the
effect sizes in terms of odds ratios (OR) and the associated
95 % confidence intervals (95 % CI). In the tables, we denote
statistical significance (pvalues at 5, 1, and 0.1 % levels,
respectively) using asterisks (*, **, and ***, respectively).
Results
STAGE cohort
In Table 1, we present the results of the binary logistic
regressions explaining self-employment (part-time/full-
time). We found a positive association with self-employ-
ment for both general ADHD symptoms (OR 1.13; 95 %
CI 1.04–1.23) and hyperactivity symptoms (OR 1.19; 95 %
CI 1.08–1.32) but not for attention-deficit symptoms (OR
0.99; 95 % CI 0.89–1.10).
GUESSS study: replication
We attempted to replicate the association between ADHD
symptoms and self-employment using the GUESSS 2011
data. The results of the binary logistic regressions are
presented in Table 2. We found no evidence of an asso-
ciation between general ADHD symptoms and self-em-
ployment (OR 1.00; 95 % CI 0.97–1.02). However, when
we separated attention-deficit and hyperactivity, we found
a negative association between self-employment and
attention-deficit symptoms (OR 0.95; 95 % CI 0.92–0.99)
and a positive association between self-employment and
hyperactivity symptoms (OR 1.09; 95 % CI 1.03–1.15).
To summarise, we found a positive association between
(general) ADHD symptoms and self-employment in the
STAGE cohort that could not be replicated (i.e.,
Table 1 STAGE cohort; Binary logistic regressions with self-em-
ployment (part-/full-time) as dependent variable and general ADHD
symptoms, and the two sub-scales attention-deficit symptoms and
hyperactivity symptoms as independent variables
(1) (2)
General ADHD symptoms 1.13**
(1.04–1.23)
Attention-deficit symptoms 0.99
(0.89–1.10)
Hyperactivity symptoms 1.19***
(1.08–1.32)
N 7208 7208
Log-likelihood -2599 -2597
df 4 5
Chi-square 209.2 222.7
Pseudo R-square 0.04 0.04
The coefficients are odds ratios (ORs) and 95 % confidence intervals
(CI) are in parentheses; *** p\0.001, ** p\0.01, * p\0.05
Both models control for age, gender, and university education
(0 =no and 1 =yes)
Table 2 GUESSS study; Binary logistic regressions with self-em-
ployment (part-/full-time) as dependent variable and general ADHD
symptoms, and the two sub-scales attention-deficit symptoms and
hyperactivity symptoms as independent variables
(1) (2)
General ADHD symptoms 0.99
(0.93–1.07)
Attention-deficit symptoms 0.89*
(0.79–1.00)
Hyperactivity symptoms 1.13*
(1.00–1.28)
N 13,119 13,119
Log-likelihood -3189 -3183
df 3 4
Chi-square 208.5 214.8
Pseudo R-square 0.07 0.07
The coefficients are odds ratios (ORs) and 95 % confidence intervals
(CI) are in parentheses; *** p\0.001, ** p\0.01, * p\0.05
Both models control for age, and gender
796 I. Verheul et al.
123
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insignificant) in the GUESSS study. Furthermore, the
association between attention-deficit symptoms and self-
employment was significantly negative in the GUESSS
study and insignificant in the STAGE cohort. Finally, the
association between hyperactivity symptoms and self-em-
ployment was significantly positive in both the STAGE
cohort and the GUESSS study.
Sensitivity and additional analyses
We performed a series of sensitivity analyses using both
the STAGE and GUESSS data. First, we reran the logistic
regressions using the entire STAGE database, including
pairs of twins instead of randomly dropping one twin, and
clustered the standard error at the family level to account
for the joint characteristics of twins. In the larger sample of
approximately 11,000 respondents, the association between
ADHD symptoms and self-employment remained intact
(OR 1.23; 95 % CI 1.13–1.34). Furthermore, the results of
the sub-scales remained stable: attention-deficit was not
significantly associated with self-employment (OR 1.02;
95 % CI 0.94–1.11), and hyperactivity was positively
associated with self-employment (OR 1.19; 95 % CI
1.10–1.29).
3
Second, to compare the results of the GUESSS study
with those of the STAGE cohort, we examined the asso-
ciations between ADHD symptoms and self-employment
in the STAGE cohort using the 6 items from the ASRS-6
v1.1 screener instead of the 18 item ASRS-v1.1 score. In
line with the GUESSS findings, we found no evidence of a
significant association between general ADHD symptoms
and self-employment (OR 1.04; 95 % CI 1.00–1.09).
However, we did not find support for a significant (nega-
tive) association between self-employment and attention-
deficit symptoms (OR 0.97; 95 % CI 0.9–1.03). We did
find a positive association between hyperactivity symptoms
and self-employment (OR 1.04; 95 % CI 1.00–1.09), which
is in agreement with the analyses.
4
Third, we examined the association between ADHD
symptoms and self-employment using a stricter definition
of ADHD that was closer to an actual psychiatric diagnosis
[10]. In the STAGE data, we used the ‘‘strict criteria’’
score: in the responses to the DSM-IV 18 items, 1 (‘‘yes’’)
was recoded to yes and 2 or 3 (‘‘yes, to some extent’’ or
‘‘no’’) were recoded to no. The outcomes supported those
of the initial analysis. The association between ADHD
symptoms and self-employment became stronger (OR:
1.35; 95 % CI 1.00–1.81), which was also true for hyper-
activity (OR: 1.54; 95 % CI 1.03–2.29). In the GUESSS
data, for each of the ASRS-6 v1.1 items, we examined
whether the score was beyond the threshold level
(‘yes =1’ and ‘no’ =‘0’) and constructed new scale
variables for ADHD symptoms, attention-deficit and
hyperactivity based on the sum of the dummy (0,1) scores
on six, four and two items, respectively. The findings
remained stable for ADHD symptoms (not significant, OR:
1.00; 95 % CI 0.93–1.07), attention-deficit (significant,
OR: 0.90; 95 % CI 0.82–0.98), and hyperactivity (signifi-
cant, OR: 1.27; 95 % CI 1.11–1.47).
Fourth, we re-estimated the logistic regressions includ-
ing additional control variables. Specifically, because
unemployment is an important push factor for self-em-
ployment [26] and because individuals who experience
ADHD symptoms have a higher chance of unemployment
[38,41], we added a control variable in the analyses with
the STAGE data that captured whether the individual had
mainly been unemployed or hardly worked in the 3 years
preceding the survey. The association between ADHD and
self-employment remained positive and significant (OR:
1.15; 95 % CI 1.06–1.25). This was also true for hyper-
activity (OR: 1.19; 95 % CI 1.07–1.32). Furthermore, we
controlled for personality characteristics of people with
ADHD symptoms. We included measures for extraversion
and neuroticism to account for the fact that ADHD
symptoms have been linked to (higher) neuroticism [42,
43] and extraversion [44]. These Big Five Factor traits have
also been linked with self-employment [45,46]. When
controlling for these two personality factors, both gen-
eral ADHD symptoms (OR: 1.17; 95 % CI 1.06–1.29) and
hyperactivity (OR: 1.14; 95 % CI 1.02–1.28) remained
significantly positive. In the analyses with the GUESSS
data, we were able to control for factors that are generally
associated with self-employment status, including self-
employed parents, study field and level. In particular,
parental role models have been linked with the decision to
become self-employed [47,48]. Accounting for the afore-
mentioned factors in the analyses, the results were stable,
and only attention-deficit and hyperactivity were signifi-
cantly associated with self-employment (attention-deficit,
OR: 0.96; 95 % CI 0.92–0.99; hyperactivity, OR: 1.07;
95 % CI 1.01–1.13).
Overall, the association between ADHD symptoms and
self-employment remained intact but became insignificant
when more controls were added. In the STAGE data, this
3
For the analyses including the ADHD symptom scale (plus
controls), the log pseudo likelihood was -2705, the pseudo R-square
was 0.06, and the Wald Chi-square was 319.4. Standard errors were
adjusted for 8434 clusters in pair ID (identifying twins). For the
analyses separating attention-deficit and hyperactivity, the log pseudo
likelihood amounted to -4118, the pseudo R-square was 0.04, and the
Wald Chi-square was 354.8. Standard errors were adjusted for 8771
clusters in pair ID.
4
In line with Kessler et al. [38,40], the reliability coefficients
(Cronbach’s alpha) for general ADHD symptoms, attention-deficit
symptoms and hyperactivity symptoms were 0.59, 0.58, and 0.50,
respectively, indicating that the scales were moderately reliable.
The association between attention-deficit/hyperactivity (ADHD) symptoms and self-employment 797
123
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was the case when considering whether someone was
mainly wage employed in the past 3 years. This is not
surprising given the fact that approximately 60 % of the
respondents were currently wage employed and had mainly
been working in wage jobs in the past 3 years. In the
GUESSS data, the association between ADHD symptoms
and self-employment appeared sensitive to the inclusion of
career motives (e.g., challenge, realising a dream, income,
financial security, innovation, opportunity exploitation,
high position, flexibility, own boss, social mission), which
may be related to the importance of the person-occupation
fit for individuals with ADHD symptoms [29].
Finally, using the STAGE data, we tested for linkages
between ADHD symptoms and other occupations. The
findings showed no association with wage employment
(OR: 0.96; 95 % CI 0.90–1.03), suggesting that a regular
wage job may not be as suitable as self-employment for
people with high levels of ADHD symptoms. Together
with our finding that ADHD symptoms are positively
associated with unemployment (OR: 1.24; 95 % CI
1.12–1.37), we are unable to reject a potential push effect
by which people with ADHD symptoms become self-em-
ployed because of a lack of (suitable) alternative
occupations.
Discussion
The present study moved beyond the clinical view of
ADHD as a pathological disorder and used the symptoms
of ADHD across the entire measurement spectrum to
examine a potentially positive aspect: the association of
ADHD with the involvement in self-employment. Hence,
the aim of this study was not to diagnose individuals with
ADHD and then examine the viability of self-employment
as a career option. Instead, we investigated whether indi-
viduals who exhibit higher levels of ADHD symptoms–but
who do not necessarily screen positive for ADHD in a
clinical sense–are positively associated with self-employ-
ment. In line with previous research, special attention was
paid to whether this association involved general ADHD
symptoms or the separate attention-deficit and hyperactiv-
ity symptom dimensions [10,34,49–51].
The present research is part of a series of investigations
on the relation between ADHD and entrepreneurship. In
Verheul et al. [29], the intention to become self-employed
was found to be associated with ADHD symptoms in a
survey of Dutch students. In Thurik et al. [52], the entre-
preneurial orientation, measured using innovativeness, risk
aversion and proactivity [53], was found to be associated
with ADHD symptoms in a survey of French business
owners. The present study investigates involvement in self-
employment. All three studies report a positive association,
although the hyperactivity part seems to dominate. Future
studies should also take into account entrepreneurial per-
formance, such as growth, profits, longevity, and
satisfaction.
Two independent samples were used for the present
analysis: Swedish adults (STAGE cohort) and Dutch stu-
dents (GUESSS study). In the Swedish sample, we found a
positive association of both general ADHD symptoms and
hyperactivity symptoms with self-employment, whereas
this association could not be found for attention-deficit
symptoms. The positive association between hyperactivity
symptoms and self-employment was replicated in the
Dutch sample. The effects remained intact in a series of
sensitivity analyses.
ADHD is typically characterised by high energy levels
that are expressed as severe and persistent attention-deficit
and hyperactivity and that are driven by behavioural ‘dis-
inhibition’ or a lack of restraint [22,41,54]. Less attention
is paid to ADHD symptoms for adult decision-making [55],
but it is generally recognised that high levels of attention-
deficit and hyperactivity have negative consequences in the
workplace. Individuals who demonstrate such behaviours
tend to show low job performance and a high chance of
becoming unemployed [56–58]. However, the present
results show that ADHD symptoms, particularly hyperac-
tivity, are associated with aspects that may be beneficial for
the individual and society at large.
The present study has implications for further research.
Our results may be an initial step towards establishing a
link between ADHD symptoms and career choices, such as
self-employment, or other manifestations of entrepreneur-
ship. The outcomes of this study may help to ‘destigmatise’
ADHD as a disorder, particularly given the positive asso-
ciations with self-employment in view of its contribution to
socio-economic life. Given the high occurrence of mod-
erate psychiatric symptoms, it is plausible (from a Dar-
winian perspective) that psychiatric symptoms not only
confer risks but can also be beneficial for the individual.
For the field of psychopathology, it is important to study
the potential benefits of demonstrating a high level of
ADHD symptoms [21,32,59,60] across the lifespan [11,
14,27,61]. Such a focus on the value (rather than the cost)
of ADHD is at the heart of a recent stream of literature in
the field of psychiatry (i.e., Darwinian Psychiatry), which
argues that the persistence of such mental ‘disorders’
serves a purpose [27,61–63]. According to this research
stream, psychiatric symptoms or genetic variations that are
mostly or currently disruptive for an individual’s work and
private life can–under some circumstances or in mild
forms–be beneficial for the ‘adaptation’ or survival of the
individual. Hence, (young) adults who experience mild to
severe ADHD symptoms may benefit rather than suffer
from them provided they find ways to cope with the
798 I. Verheul et al.
123
Content courtesy of Springer Nature, terms of use apply. Rights reserved.

negative consequences in general and in relation to an
entrepreneurial context [22]. Benefits may be particularly
salient when individuals with ADHD symptoms find a
suitable work environment, such as self-employment,
where the ‘disorder’ is not harmful but instead can be
valuable and help them to function well in society [21,27,
61].
Although the present study only investigates one single
outcome, self-employment as a possibly positive aspect of
ADHD symptoms, it highlights some promising avenues
for future research. First, the current data do not enable us
to examine the association between ADHD symptoms and
the performance of self-employed individuals. The ques-
tion that arises is whether self-employed individuals who
score higher on ADHD symptoms also have better-per-
forming ventures [53]. Second, the decision to become
self-employed may not be the only association with ADHD
symptoms; underlying entrepreneurial behaviours such as
risk-taking and proactivity may share this association [52].
ADHD symptoms may also have ‘positive’ associations
with other socio-economic behaviours for occupational
choice, such as in management and consultancy positions
[24]. Third, to generalise the results of this study, it is
worthwhile to examine the association between ADHD
symptoms and self-employment in other, preferably non-
European, population-based cohorts. It is also important to
distinguish between individuals with a different occupa-
tional status in the control group, including wage
employment and unemployment. A first attempt is reported
in our section on sensitivity analyses. For future research, it
is important to distinguish between these (alternative)
occupations to effectively examine the association with
different control groups.
To conclude, our results indicate that the positive
association between ADHD symptoms and the decision to
become self-employed primarily hinges on the hyperac-
tivity symptoms of ADHD, whereas the overall association
between ADHD symptoms and self-employment is only
significant in one of our two samples. For future research, it
is important to understand how ADHD symptoms are
associated with more specific self-employment and
entrepreneurship behaviours, such as the level of risks
taken or performance in self-employment or as a business
owner. This research may enhance our understanding of the
positive effects of ADHD symptoms or even ‘destigmatise’
ADHD as a disorder that always deserves treatment.
Compliance with ethical standards
Conflicts of interest The authors have no conflicts of interest to
declare.
Ethical statement This study was conducted according to the
guidelines in the Declaration of Helsinki. The STAGE cohort study
was approved by the ethics committee of Karolinska Institutet,
Stockholm, Sweden, and all participants provided written informed
consent. The GUESSS study was in line with the Erasmus Research
Institute of Management (ERIM) review board’s standards and did
not include clinical or patient data.
Open Access This article is distributed under the terms of the
Creative Commons Attribution 4.0 International License (http://crea
tivecommons.org/licenses/by/4.0/), which permits unrestricted use,
distribution, and reproduction in any medium, provided you give
appropriate credit to the original author(s) and the source, provide a
link to the Creative Commons license, and indicate if changes were
made.
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