573992
research-article2015
JADXXX10.1177/1087054715573992Journal of Attention DisordersHesson and Fowler
Article
Prevalence and Correlates of Self-Reported ADD/ADHD in a Large National Sample of Canadian Adults
Journal of Attention Disorders 1–10 © 2015 SAGE Publications Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/1087054715573992 jad.sagepub.com
Jacqueline Hesson1 and Ken Fowler1
Abstract Objective: The objective of this study was to examine the prevalence and correlates of self-reported attention deficit disorder (ADD)/ADHD in Canadian adults. Method: Prevalence of self-reported ADD/ADHD was examined in a large national sample of Canadians (n = 16,957). Demographic variables, lifetime, and current psychiatric comorbidities were then compared in a group of adults with self-reported ADD/ADHD (n = 488) and an age- and gender-matched control group (n = 488). Results: The prevalence of self-reported ADD/ADHD was 2.9%. Significantly higher lifetime and current prevalence rates of major depressive disorder, bipolar I and II disorders, generalized anxiety disorder, and substance use disorders were observed in the ADD/ADHD group compared with the control group. Within the ADD/ADHD group, lifetime and 12-month prevalence rates of major depressive disorder and generalized anxiety disorder were significantly higher in women, whereas lifetime and current rates of some substance use disorders were significantly higher in men. Conclusion: In a national sample of Canadian adults, self-reported ADD/ADHD was associated with significant psychiatric comorbidity. Gender differences were also noted. (J. of Att. Dis. XXXX; XX(X) XX-XX) Keywords ADD/ADHD, adult, comorbidity, prevalence With an estimated worldwide-pooled prevalence of 5.3% (Polanczyk, de Lima, Horta, Biederman, & Rohde, 2007), ADHD is one of the most common neuropsychiatric disorders of childhood. Characterized by symptoms of inattention, hyperactivity, and difficulties with impulsivity, ADHD was originally thought to remit by young adulthood. However, long-term follow-up studies indicate that, to varying degrees, the symptoms of the disorder persist well into adulthood in 50% to 78% of individuals (Biederman, Petty, Evans, Small, & Faraone, 2010; Lara et al., 2009) with symptoms still being seen in individuals above the age of 65 years (Michielsen et al., 2012). In addition to adults who were diagnosed with ADHD as children and adolescents, there are a significant number of individuals being diagnosed for the first time as adults (Piñeiro-Dieguez, Balanzá-Martinez, Garcia-Garcia, & Soler-López, 2014). With the recognition that ADHD can continue throughout the life span, the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5; American Psychiatric Association, 2013) now includes a definition of ADHD which captures the nature of the disorder as it is experienced by adults. While difficulties with inattention and impulsivity are noted to persist into adulthood, hyperactivity becomes less apparent and is manifested by feelings of restlessness (American Psychiatric Association, 2013). A
meta-analysis of available population-based studies puts the prevalence rate of ADHD in adults at 2.5% (Simon, Czobor, Balint, Meszaros, & Bitter, 2009). In children and adolescents, rates of ADHD are consistently reported as being significantly higher in boys than girls with current estimates of the male to female ratio worldwide ranging from 2:1 (Polanczyk et al., 2007) to 3:1 (Erskine et al., 2013). It appears that this gender imbalance persists into adulthood, with an approximate male to female ratio of 2.4 to 1 (Polanczyk & Jensen, 2008). The symptoms of ADHD significantly affect the social (Greene et al., 2001; Ronk, Hund, & Landau, 2011; Thorell & Rydell, 2008) and academic functioning (DuPaul et al., 2006; Polderman, Boomsma, Bartels, Verhulst, & Huizink, 2010) of affected children and adolescents. Relative to their peers without ADHD, children and adolescents also present with increased rates of Axis I disorders such as mood disorders, anxiety disorders, substance use disorders (SUDs), learning disorders (LDs), eating disorders (EDs), oppositional 1
Memorial University of Newfoundland, St. John’s, Canada
Corresponding Author: Jacqueline Hesson, Faculty of Education, Memorial University of Newfoundland, St. John’s, Newfoundland A1B 3X9, Canada. Email: [email protected]
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Journal of Attention Disorders
defiant disorder (ODD), and conduct disorder (CD; Biederman et al., 2002; Növik et al., 2006; Rucklidge, 2010). Consensus regarding the role of gender in the comorbidities of ADHD in children has yet to be reached with Biederman et al. (2005) suggesting that any observed gender differences are more likely to be the result of a referral bias (i.e., that it is disruptive behavior, more commonly seen in boys with ADHD, that drives referrals) than a true gender effect. While the symptoms of ADHD may modulate in terms of presentation and attenuate in severity as individuals move from childhood into adulthood, their impact on a number of areas of day-to-day functioning is still significant. In comparison with adults without ADHD, adults with ADHD are more likely to have lower educational attainment (Biederman et al., 2012; Breslin & Pole, 2009; Gjervan, Torgersen, Nordahl, & Rasmussen, 2012), lower occupational achievement (Breslin & Pole, 2009), a higher risk of being fired (Barkley & Murphy, 2010) and unemployed (Biederman et al., 2012; Das, Cherbuin, Butterworth, Anstey, & Easteal, 2012; Fletcher, 2014; Gjervan et al., 2012; Huntley & Young, 2014), and be at an increased risk of workplace injury (Breslin & Pole, 2009). In terms of social functioning, adults with ADHD experience higher levels of marital and family dysfunction (Eakin et al., 2004) and view themselves as less socially competent than others without ADHD (Friedman et al., 2003). In addition, adults with ADHD are more likely than adults without ADHD to be involved with the criminal justice system (Young et al., 2011) and to be incarcerated (Cahill et al., 2012). In addition to the functional difficulties associated with ADHD, studies indicate that, relative to adults without ADHD, adults with ADHD experience higher levels of anxiety and mood disorders (Biederman et al., 2012; Fayyad et al., 2007; Friedrichs, Igl, Larsson, & Larsson, 2012; Kessler et al., 2006; Michielsen et al., 2013; Van Ameringen, Mancini, Simpson, & Patterson, 2011) and are more likely to have issues with alcohol and substance abuse and dependence (Fayyad et al., 2007; Gjervan et al., 2012; Huntley & Young, 2014; Kessler et al., 2006; Piñeiro-Dieguez et al., 2014). Whereas some studies report no or only minor gender differences in the comorbidities associated with ADHD in adults (Biederman, Faraone, Monuteaux, Bober, & Cadogen, 2004; Friedrichs et al., 2012; Rucklidge, DownsWooley, Taylor, Brown, & Harrow, 2014), other studies indicate that men are more likely to have higher rates of substance abuse (Cumyn, French, & Hechtman, 2009; Piñeiro et al., 2014; Soendergaard et al., 2014) and women are more likely to have higher rates of EDs (Cumyn et al., 2009; Groß-Lesch et al., 2013; Piñeiro-Dieguez et al., 2014), mood disorders (Groß-Lesch et al., 2013; PiñeiroDieguez et al., 2014; Rasmussen & Levander, 2009), and anxiety disorders (Cumyn et al., 2009; Groß-Lesch et al., 2013).
To date, very little is known regarding the prevalence and comorbidities of ADHD in Canadian adults. The aims of the present study were to estimate the prevalence of selfreported ADHD in Canadians aged 20 to 64 years and to compare the prevalence of psychiatric diagnoses in individuals with self-reported attention deficit disorder (ADD)/ ADHD with that observed in an age- and gender-matched sample of individuals without ADD/ADHD. Gender differences were also examined.
Method Participants Data from the Public Use Microdata File of the Canadian Community Health Survey–Mental Health (CCHS-MH) 2012 (Statistics Canada, 2013) were analyzed. The CCHS-MH is a national mental health survey designed, in part, to assess the mental health status of Canadians in terms of selected mental health disorders, to assess functioning in relation to mental health, and to examine potential links between mental health and sociodemographic variables. Respondents for the survey were selected in three stages. First, geographical areas were selected, followed by households within each geographical area. Finally, one respondent from each household was randomly selected. The national response rate for the survey was 68.9% with the CCHS-MH providing cross-sectional data from 25,113 Canadians aged 15 years or older who were residing in private residences in the 10 provinces at the time of the survey. The survey sample does not include individuals living in the three Canadian territories, individuals living on reserves, full-time members of the Canadian Forces, or individuals who are institutionalized. Statistics Canada (2013) estimates the total number of individuals excluded from the survey to represent less than 3% of the target population. In the survey database, age is recorded categorically and ranges from “15 to 19 years” to “80 years or older.” As the focus of the present study was adults, individuals in the age category “15 to 19 years” were not included in the analyses. To allow for comparison with other prevalence studies (Ramos-Quiroga, Montoya, Kutzelnigg, Deberdt, & Sobanski, 2013), individuals aged 65 years and older were also not included in the analyses. In addition, data from individuals who did not provide a response when asked whether they had been diagnosed by a health professional with ADD were excluded from the analyses. As a result, the final survey sample size consisted of 16,957 individuals.
Data Collection The majority of interviews (87%) for the CCHS-MH (Statistics Canada, 2013) were conducted in person with the remaining interviews completed via telephone. No proxy
Downloaded from jad.sagepub.com at OAKLAND UNIV on May 2, 2015
3
Hesson and Fowler interviews were allowed. Interviews were conducted by lay people trained by representatives from Statistics Canada’s Collection Planning and Management Division. Interviews were completed using the computer-assisted personal interviewing (CAPI) method which allows for customs interviews for each respondent based on their individual characteristics and survey results, ensuring that interviewers do not ask questions that do not apply to the respondent (Statistics Canada, 2013). Data were collected during the period from January to December 2012.
Sociodemographic variables. Sociodemographic variables were categorical in nature and included gender (male, female), age (20-24, 25-29, 30-34, 35-39, 40-44, 45-49, 50-54, 55-59, 60-64), education (less than secondary school graduation, secondary school graduation, some post-secondary, and post-secondary graduation), personal income in Canadian dollars (less than $10,000, $10,000-$19,999, $20,000-$29,999, $30,000-$39,999, $40,000-$49,999, and $50,000 and above), and marital status (married, commonlaw, divorced or separated, widowed, and single).
Materials
Statistical analysis. Prevalence of ADD/ADHD was determined based on the number of individuals in the entire sample of individuals aged 20 to 64 years who responded “yes” to the question of whether they had been diagnosed by a health professional with an ADD. Derived lifetime and 12-month frequencies of MDD, BPD I and II, GAD, alcohol abuse and dependence, cannabis abuse and dependence, and other drug (not including cannabis) abuse and dependence were examined. Comparisons were made (a) between individuals reporting a diagnosis of ADD/ADHD and a control group consisting of an equivalent number of ageand gender-matched individuals randomly selected from the overall sample who did not report being diagnosed with ADD/ADHD and (b) between men and women reporting a diagnosis of ADD/ADHD. Chi-square tests were performed to examine gender differences and differences between the ADD/ADHD and control groups.
Self-report of ADHD. As part of the CCHS interview, participants were asked to indicate whether they had been diagnosed by a health professional with a variety of mental health conditions that had lasted or were expected to last for 6 months or longer. One of these questions was “Do you have attention deficit disorder?” Assessment of psychiatric disorders—Lifetime and 12-month prevalence. To reduce respondent burden, the survey modules for depression, mania, and generalized anxiety disorder (GAD) are preceded by a section with screener questions for each disorder. Participants who responded “no” to the screening questions were not asked questions from the module associated with that disorder and were categorized as failing to meet the criteria for that disorder. The alcohol abuse and dependence and substance use, abuse, and dependence modules do not require screening questions as all respondents are administered a minimum set of questions on their use of alcohol and drugs. The questions used for the CCHS-MH modules on alcohol abuse and dependence, substance abuse and dependence, major depressive disorder (MDD), bipolar I and II disorders (BPD I and II), and GAD are based on a recognized World Health Organization version of the Composite International Diagnostic Interview (WHO-CIDI) modified for the needs of CCHS-MH (Statistics Canada, 2013). The WHO-CIDI is a standardized instrument for the assessment of mental disorders and conditions based on the definitions and criteria of Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association, 1994) and International Classification of Diseases and Related Health Problems (ICD-10; World Health Organization, 1992). Mental conditions or problems found in the CCHS-MH are partially coded to DSM-IV (Statistics Canada, 2013). Computer-based algorithms were used to calculate lifetime criteria for each disorder based on respondents’ answers to the questions within each disorder module. For each disorder, 12-month criteria included meeting the criteria for a lifetime diagnosis of the disorder, experiencing an episode of the disorder within the previous 12 months, and experiencing a marked impairment in occupational and social functioning.
Results Prevalence of Self-Reported Diagnosis of ADD/ ADHD Of the total sample of respondents, 488 (2.9% of the total Canadian sample aged 20-64 years) reported having been diagnosed with ADD/ADHD by a health professional. Significantly more men (n = 287, 58.8%) than women (n = 201, 41.2%) reported a diagnosis of ADD/ADHD, χ2(1) = 31.577, p < .0001.
Sociodemographic Variables Frequency analyses for demographics for the ADD/ADHD and control groups and for men and women reporting a diagnosis of ADD/ADHD are shown in Table 1. For education, a chi-square test was significant, χ2(3) = 18.520, p < .0001, suggesting that, in comparison with the control group, individuals in the ADD/ADHD group were more likely to report not having completed high school. No gender differences were observed between men and women in the ADD/ADHD group for level of education, χ2(3) = 2.663, p = .447. In terms of total personal income, a chi-square test was significant, χ2(5) = 49.27, p < .0001, and suggested
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Journal of Attention Disorders
Table 1. Sociodemographic Frequencies for Individuals Reporting a Diagnosis of ADD/ADHD and Individuals not Reporting a Diagnosis of ADD/ADHD. Frequency, n (%) Sociodemographic variable Age (years) 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 Education Less than secondary school Secondary school graduation Some post-secondary Post-secondary graduation Not stated Personal income Less than $10,000 $10,00-$19,999 $20,000-$29,999 $30,000-$39,999 $40,000-$49,999 $50,000 or more Not stated Marital status Married Common-law Widowed Divorced/separated Single Not stated
ADD/ADHD (total)
Control
ADD/ADHD (men)
ADD/ADHD (women)
N = 488
n = 488
n = 287
n = 201
101 (20.7) 82 (16.8) 55 (11.3) 55 (11.3) 57 (11.7) 41 (8.4) 35 (7.2) 34 (7.0) 28 (5.7)
101 (20.7) 82 (16.8) 55 (11.3) 55 (11.3) 57 (11.7) 41 (8.4) 35 (7.2) 34 (7.0) 28 (5.7)
65 (22.6) 54 (18.8) 33 (11.5) 34 (11.8) 34 (11.8) 21 (7.3) 20 (7.0) 14 (4.9) 12 (4.2)
36 (17.9) 28 (13.9) 22 (10.9) 21 (10.4) 23 (11.4) 20 (10.0) 15 (7.5) 20 (10.0) 16 (8.0)
86 (17.6) 94 (19.3) 52 (10.7) 252 (51.6) 4 (0.8)
47 (9.6) 97 (19.9) 38 (7.8) 304 (62.3) 2 (0.4)
48 (16.7) 61 (21.3) 33 (11.5) 143 (49.8) 2 (0.7)
38 (18.9) 33 (16.4) 19 (9.5) 109 (54.2) 2 (1.0)
27 (5.5) 129 (26.4) 102 (20.9) 56 (11.5) 48 (9.8) 81 (16.6) 45 (9.2)
27 (5.5) 56 (11.5) 109 (22.3) 61 (12.5) 39 (7.9) 147 (30.1) 49 (10.0)
12 (4.2) 62 (21.6) 63 (22.0) 35 (12.2) 35 (12.2) 52 (18.1) 28 (9.8)
15 (7.5) 67 (33.3) 39 (19.4) 21 (10.0) 13 (6.5) 29 (14.4) 17 (8.5)
109 (22.3) 72 (14.7) 7 (1.4) 71 (14.5) 227 (46.5) 2 (0.4)
166 (34.0) 73 (15.0) 7 (1.4) 42 (8.6) 198 (40.6) 2 (0.4)
62 (21.6) 37 (12.9) 1 (0.3) 33 (11.5) 154 (53.7) 0 (0)
47 (23.4) 35 (17.4) 6 (3.0) 38 (18.9) 73 (36.3) 2 (1.0)
Note. ADD = attention deficit disorder.
that, as compared with the control group, individuals in the ADD/ADHD group more frequently reported a personal income in the $10,000 to $19,999 range and less frequently reported an income above $50,000. A significant gender difference was also observed in reported income level within the ADD/ADHD group, χ2(5) = 13.992, p < .05. About 40.8% of women in the ADD/ADHD group reported personal income below $19,999 compared with 25.8% of men. In addition, 30.3% of men in the ADD/ADHD group reported an income above $40,000 compared with 20.9% of women reporting a diagnosis of ADD/ADHD. Significant differences in marital status were also noted between the ADD/ADHD group and the control group, χ2(4) = 21.24, p < .0001. Compared with the control group, individuals in the ADD/ADHD group less frequently reported being
married but more frequently reported being separated or divorced. Significant gender differences in marital status were observed in the ADD/ADHD group, χ2(4) = 19.657, p = .001, with men more frequently reporting being single.
Comorbid Diagnoses Table 2 shows the frequency with which individuals in the ADD/ADHD and control groups meet criteria for lifetime and current (12-month) psychiatric diagnoses. Significant group differences were found in the frequency of lifetime psychiatric diagnoses with individuals in the ADD/ADHD group meeting criteria for a lifetime diagnosis of all disorders significantly more frequently than individuals in the control group. Individuals in the ADD/ADHD group also
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Hesson and Fowler Table 2. Lifetime Prevalence Rates of Psychiatric Diagnoses in the ADD/ADHD and Control Groups. Frequency, n (%) Psychiatric disorder Lifetime Major depressive disorder Bipolar disorder I Bipolar disorder II Generalized anxiety disorder Alcohol abuse Alcohol dependence Cannabis abuse Cannabis dependence Other drug abuse Other drug dependence 12-month Major depressive disorder Bipolar disorder I Bipolar disorder II Generalized anxiety disorder Alcohol abuse Alcohol dependence Cannabis abuse Cannabis dependence Other drug abuse Other drug dependence
ADD/ADHD (n = 488)
Control (n = 488)
χ2
p
175 (36.0) 31 (6.4) 16 (3.3) 165 (34.0) 127 (26.3) 68 (14.2) 75 (15.5) 42 (8.7) 49 (10.1) 65 (13.5)
61 (12.5) 3 (0.6) 6 (1.2) 47 (9.7) 95 (19.7) 14 (2.9) 35 (7.2) 10 (2.1) 17 (3.5) 14 (2.9)
73.01 24.13 4.757 84.34 5.989 39.37 16.50 20.74 16.72 35.97
research-article2015
JADXXX10.1177/1087054715573992Journal of Attention DisordersHesson and Fowler
Article
Prevalence and Correlates of Self-Reported ADD/ADHD in a Large National Sample of Canadian Adults
Journal of Attention Disorders 1–10 © 2015 SAGE Publications Reprints and permissions: sagepub.com/journalsPermissions.nav DOI: 10.1177/1087054715573992 jad.sagepub.com
Jacqueline Hesson1 and Ken Fowler1
Abstract Objective: The objective of this study was to examine the prevalence and correlates of self-reported attention deficit disorder (ADD)/ADHD in Canadian adults. Method: Prevalence of self-reported ADD/ADHD was examined in a large national sample of Canadians (n = 16,957). Demographic variables, lifetime, and current psychiatric comorbidities were then compared in a group of adults with self-reported ADD/ADHD (n = 488) and an age- and gender-matched control group (n = 488). Results: The prevalence of self-reported ADD/ADHD was 2.9%. Significantly higher lifetime and current prevalence rates of major depressive disorder, bipolar I and II disorders, generalized anxiety disorder, and substance use disorders were observed in the ADD/ADHD group compared with the control group. Within the ADD/ADHD group, lifetime and 12-month prevalence rates of major depressive disorder and generalized anxiety disorder were significantly higher in women, whereas lifetime and current rates of some substance use disorders were significantly higher in men. Conclusion: In a national sample of Canadian adults, self-reported ADD/ADHD was associated with significant psychiatric comorbidity. Gender differences were also noted. (J. of Att. Dis. XXXX; XX(X) XX-XX) Keywords ADD/ADHD, adult, comorbidity, prevalence With an estimated worldwide-pooled prevalence of 5.3% (Polanczyk, de Lima, Horta, Biederman, & Rohde, 2007), ADHD is one of the most common neuropsychiatric disorders of childhood. Characterized by symptoms of inattention, hyperactivity, and difficulties with impulsivity, ADHD was originally thought to remit by young adulthood. However, long-term follow-up studies indicate that, to varying degrees, the symptoms of the disorder persist well into adulthood in 50% to 78% of individuals (Biederman, Petty, Evans, Small, & Faraone, 2010; Lara et al., 2009) with symptoms still being seen in individuals above the age of 65 years (Michielsen et al., 2012). In addition to adults who were diagnosed with ADHD as children and adolescents, there are a significant number of individuals being diagnosed for the first time as adults (Piñeiro-Dieguez, Balanzá-Martinez, Garcia-Garcia, & Soler-López, 2014). With the recognition that ADHD can continue throughout the life span, the Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5; American Psychiatric Association, 2013) now includes a definition of ADHD which captures the nature of the disorder as it is experienced by adults. While difficulties with inattention and impulsivity are noted to persist into adulthood, hyperactivity becomes less apparent and is manifested by feelings of restlessness (American Psychiatric Association, 2013). A
meta-analysis of available population-based studies puts the prevalence rate of ADHD in adults at 2.5% (Simon, Czobor, Balint, Meszaros, & Bitter, 2009). In children and adolescents, rates of ADHD are consistently reported as being significantly higher in boys than girls with current estimates of the male to female ratio worldwide ranging from 2:1 (Polanczyk et al., 2007) to 3:1 (Erskine et al., 2013). It appears that this gender imbalance persists into adulthood, with an approximate male to female ratio of 2.4 to 1 (Polanczyk & Jensen, 2008). The symptoms of ADHD significantly affect the social (Greene et al., 2001; Ronk, Hund, & Landau, 2011; Thorell & Rydell, 2008) and academic functioning (DuPaul et al., 2006; Polderman, Boomsma, Bartels, Verhulst, & Huizink, 2010) of affected children and adolescents. Relative to their peers without ADHD, children and adolescents also present with increased rates of Axis I disorders such as mood disorders, anxiety disorders, substance use disorders (SUDs), learning disorders (LDs), eating disorders (EDs), oppositional 1
Memorial University of Newfoundland, St. John’s, Canada
Corresponding Author: Jacqueline Hesson, Faculty of Education, Memorial University of Newfoundland, St. John’s, Newfoundland A1B 3X9, Canada. Email: [email protected]
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Journal of Attention Disorders
defiant disorder (ODD), and conduct disorder (CD; Biederman et al., 2002; Növik et al., 2006; Rucklidge, 2010). Consensus regarding the role of gender in the comorbidities of ADHD in children has yet to be reached with Biederman et al. (2005) suggesting that any observed gender differences are more likely to be the result of a referral bias (i.e., that it is disruptive behavior, more commonly seen in boys with ADHD, that drives referrals) than a true gender effect. While the symptoms of ADHD may modulate in terms of presentation and attenuate in severity as individuals move from childhood into adulthood, their impact on a number of areas of day-to-day functioning is still significant. In comparison with adults without ADHD, adults with ADHD are more likely to have lower educational attainment (Biederman et al., 2012; Breslin & Pole, 2009; Gjervan, Torgersen, Nordahl, & Rasmussen, 2012), lower occupational achievement (Breslin & Pole, 2009), a higher risk of being fired (Barkley & Murphy, 2010) and unemployed (Biederman et al., 2012; Das, Cherbuin, Butterworth, Anstey, & Easteal, 2012; Fletcher, 2014; Gjervan et al., 2012; Huntley & Young, 2014), and be at an increased risk of workplace injury (Breslin & Pole, 2009). In terms of social functioning, adults with ADHD experience higher levels of marital and family dysfunction (Eakin et al., 2004) and view themselves as less socially competent than others without ADHD (Friedman et al., 2003). In addition, adults with ADHD are more likely than adults without ADHD to be involved with the criminal justice system (Young et al., 2011) and to be incarcerated (Cahill et al., 2012). In addition to the functional difficulties associated with ADHD, studies indicate that, relative to adults without ADHD, adults with ADHD experience higher levels of anxiety and mood disorders (Biederman et al., 2012; Fayyad et al., 2007; Friedrichs, Igl, Larsson, & Larsson, 2012; Kessler et al., 2006; Michielsen et al., 2013; Van Ameringen, Mancini, Simpson, & Patterson, 2011) and are more likely to have issues with alcohol and substance abuse and dependence (Fayyad et al., 2007; Gjervan et al., 2012; Huntley & Young, 2014; Kessler et al., 2006; Piñeiro-Dieguez et al., 2014). Whereas some studies report no or only minor gender differences in the comorbidities associated with ADHD in adults (Biederman, Faraone, Monuteaux, Bober, & Cadogen, 2004; Friedrichs et al., 2012; Rucklidge, DownsWooley, Taylor, Brown, & Harrow, 2014), other studies indicate that men are more likely to have higher rates of substance abuse (Cumyn, French, & Hechtman, 2009; Piñeiro et al., 2014; Soendergaard et al., 2014) and women are more likely to have higher rates of EDs (Cumyn et al., 2009; Groß-Lesch et al., 2013; Piñeiro-Dieguez et al., 2014), mood disorders (Groß-Lesch et al., 2013; PiñeiroDieguez et al., 2014; Rasmussen & Levander, 2009), and anxiety disorders (Cumyn et al., 2009; Groß-Lesch et al., 2013).
To date, very little is known regarding the prevalence and comorbidities of ADHD in Canadian adults. The aims of the present study were to estimate the prevalence of selfreported ADHD in Canadians aged 20 to 64 years and to compare the prevalence of psychiatric diagnoses in individuals with self-reported attention deficit disorder (ADD)/ ADHD with that observed in an age- and gender-matched sample of individuals without ADD/ADHD. Gender differences were also examined.
Method Participants Data from the Public Use Microdata File of the Canadian Community Health Survey–Mental Health (CCHS-MH) 2012 (Statistics Canada, 2013) were analyzed. The CCHS-MH is a national mental health survey designed, in part, to assess the mental health status of Canadians in terms of selected mental health disorders, to assess functioning in relation to mental health, and to examine potential links between mental health and sociodemographic variables. Respondents for the survey were selected in three stages. First, geographical areas were selected, followed by households within each geographical area. Finally, one respondent from each household was randomly selected. The national response rate for the survey was 68.9% with the CCHS-MH providing cross-sectional data from 25,113 Canadians aged 15 years or older who were residing in private residences in the 10 provinces at the time of the survey. The survey sample does not include individuals living in the three Canadian territories, individuals living on reserves, full-time members of the Canadian Forces, or individuals who are institutionalized. Statistics Canada (2013) estimates the total number of individuals excluded from the survey to represent less than 3% of the target population. In the survey database, age is recorded categorically and ranges from “15 to 19 years” to “80 years or older.” As the focus of the present study was adults, individuals in the age category “15 to 19 years” were not included in the analyses. To allow for comparison with other prevalence studies (Ramos-Quiroga, Montoya, Kutzelnigg, Deberdt, & Sobanski, 2013), individuals aged 65 years and older were also not included in the analyses. In addition, data from individuals who did not provide a response when asked whether they had been diagnosed by a health professional with ADD were excluded from the analyses. As a result, the final survey sample size consisted of 16,957 individuals.
Data Collection The majority of interviews (87%) for the CCHS-MH (Statistics Canada, 2013) were conducted in person with the remaining interviews completed via telephone. No proxy
Downloaded from jad.sagepub.com at OAKLAND UNIV on May 2, 2015
3
Hesson and Fowler interviews were allowed. Interviews were conducted by lay people trained by representatives from Statistics Canada’s Collection Planning and Management Division. Interviews were completed using the computer-assisted personal interviewing (CAPI) method which allows for customs interviews for each respondent based on their individual characteristics and survey results, ensuring that interviewers do not ask questions that do not apply to the respondent (Statistics Canada, 2013). Data were collected during the period from January to December 2012.
Sociodemographic variables. Sociodemographic variables were categorical in nature and included gender (male, female), age (20-24, 25-29, 30-34, 35-39, 40-44, 45-49, 50-54, 55-59, 60-64), education (less than secondary school graduation, secondary school graduation, some post-secondary, and post-secondary graduation), personal income in Canadian dollars (less than $10,000, $10,000-$19,999, $20,000-$29,999, $30,000-$39,999, $40,000-$49,999, and $50,000 and above), and marital status (married, commonlaw, divorced or separated, widowed, and single).
Materials
Statistical analysis. Prevalence of ADD/ADHD was determined based on the number of individuals in the entire sample of individuals aged 20 to 64 years who responded “yes” to the question of whether they had been diagnosed by a health professional with an ADD. Derived lifetime and 12-month frequencies of MDD, BPD I and II, GAD, alcohol abuse and dependence, cannabis abuse and dependence, and other drug (not including cannabis) abuse and dependence were examined. Comparisons were made (a) between individuals reporting a diagnosis of ADD/ADHD and a control group consisting of an equivalent number of ageand gender-matched individuals randomly selected from the overall sample who did not report being diagnosed with ADD/ADHD and (b) between men and women reporting a diagnosis of ADD/ADHD. Chi-square tests were performed to examine gender differences and differences between the ADD/ADHD and control groups.
Self-report of ADHD. As part of the CCHS interview, participants were asked to indicate whether they had been diagnosed by a health professional with a variety of mental health conditions that had lasted or were expected to last for 6 months or longer. One of these questions was “Do you have attention deficit disorder?” Assessment of psychiatric disorders—Lifetime and 12-month prevalence. To reduce respondent burden, the survey modules for depression, mania, and generalized anxiety disorder (GAD) are preceded by a section with screener questions for each disorder. Participants who responded “no” to the screening questions were not asked questions from the module associated with that disorder and were categorized as failing to meet the criteria for that disorder. The alcohol abuse and dependence and substance use, abuse, and dependence modules do not require screening questions as all respondents are administered a minimum set of questions on their use of alcohol and drugs. The questions used for the CCHS-MH modules on alcohol abuse and dependence, substance abuse and dependence, major depressive disorder (MDD), bipolar I and II disorders (BPD I and II), and GAD are based on a recognized World Health Organization version of the Composite International Diagnostic Interview (WHO-CIDI) modified for the needs of CCHS-MH (Statistics Canada, 2013). The WHO-CIDI is a standardized instrument for the assessment of mental disorders and conditions based on the definitions and criteria of Diagnostic and Statistical Manual of Mental Disorders (4th ed.; DSM-IV; American Psychiatric Association, 1994) and International Classification of Diseases and Related Health Problems (ICD-10; World Health Organization, 1992). Mental conditions or problems found in the CCHS-MH are partially coded to DSM-IV (Statistics Canada, 2013). Computer-based algorithms were used to calculate lifetime criteria for each disorder based on respondents’ answers to the questions within each disorder module. For each disorder, 12-month criteria included meeting the criteria for a lifetime diagnosis of the disorder, experiencing an episode of the disorder within the previous 12 months, and experiencing a marked impairment in occupational and social functioning.
Results Prevalence of Self-Reported Diagnosis of ADD/ ADHD Of the total sample of respondents, 488 (2.9% of the total Canadian sample aged 20-64 years) reported having been diagnosed with ADD/ADHD by a health professional. Significantly more men (n = 287, 58.8%) than women (n = 201, 41.2%) reported a diagnosis of ADD/ADHD, χ2(1) = 31.577, p < .0001.
Sociodemographic Variables Frequency analyses for demographics for the ADD/ADHD and control groups and for men and women reporting a diagnosis of ADD/ADHD are shown in Table 1. For education, a chi-square test was significant, χ2(3) = 18.520, p < .0001, suggesting that, in comparison with the control group, individuals in the ADD/ADHD group were more likely to report not having completed high school. No gender differences were observed between men and women in the ADD/ADHD group for level of education, χ2(3) = 2.663, p = .447. In terms of total personal income, a chi-square test was significant, χ2(5) = 49.27, p < .0001, and suggested
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Journal of Attention Disorders
Table 1. Sociodemographic Frequencies for Individuals Reporting a Diagnosis of ADD/ADHD and Individuals not Reporting a Diagnosis of ADD/ADHD. Frequency, n (%) Sociodemographic variable Age (years) 20-24 25-29 30-34 35-39 40-44 45-49 50-54 55-59 60-64 Education Less than secondary school Secondary school graduation Some post-secondary Post-secondary graduation Not stated Personal income Less than $10,000 $10,00-$19,999 $20,000-$29,999 $30,000-$39,999 $40,000-$49,999 $50,000 or more Not stated Marital status Married Common-law Widowed Divorced/separated Single Not stated
ADD/ADHD (total)
Control
ADD/ADHD (men)
ADD/ADHD (women)
N = 488
n = 488
n = 287
n = 201
101 (20.7) 82 (16.8) 55 (11.3) 55 (11.3) 57 (11.7) 41 (8.4) 35 (7.2) 34 (7.0) 28 (5.7)
101 (20.7) 82 (16.8) 55 (11.3) 55 (11.3) 57 (11.7) 41 (8.4) 35 (7.2) 34 (7.0) 28 (5.7)
65 (22.6) 54 (18.8) 33 (11.5) 34 (11.8) 34 (11.8) 21 (7.3) 20 (7.0) 14 (4.9) 12 (4.2)
36 (17.9) 28 (13.9) 22 (10.9) 21 (10.4) 23 (11.4) 20 (10.0) 15 (7.5) 20 (10.0) 16 (8.0)
86 (17.6) 94 (19.3) 52 (10.7) 252 (51.6) 4 (0.8)
47 (9.6) 97 (19.9) 38 (7.8) 304 (62.3) 2 (0.4)
48 (16.7) 61 (21.3) 33 (11.5) 143 (49.8) 2 (0.7)
38 (18.9) 33 (16.4) 19 (9.5) 109 (54.2) 2 (1.0)
27 (5.5) 129 (26.4) 102 (20.9) 56 (11.5) 48 (9.8) 81 (16.6) 45 (9.2)
27 (5.5) 56 (11.5) 109 (22.3) 61 (12.5) 39 (7.9) 147 (30.1) 49 (10.0)
12 (4.2) 62 (21.6) 63 (22.0) 35 (12.2) 35 (12.2) 52 (18.1) 28 (9.8)
15 (7.5) 67 (33.3) 39 (19.4) 21 (10.0) 13 (6.5) 29 (14.4) 17 (8.5)
109 (22.3) 72 (14.7) 7 (1.4) 71 (14.5) 227 (46.5) 2 (0.4)
166 (34.0) 73 (15.0) 7 (1.4) 42 (8.6) 198 (40.6) 2 (0.4)
62 (21.6) 37 (12.9) 1 (0.3) 33 (11.5) 154 (53.7) 0 (0)
47 (23.4) 35 (17.4) 6 (3.0) 38 (18.9) 73 (36.3) 2 (1.0)
Note. ADD = attention deficit disorder.
that, as compared with the control group, individuals in the ADD/ADHD group more frequently reported a personal income in the $10,000 to $19,999 range and less frequently reported an income above $50,000. A significant gender difference was also observed in reported income level within the ADD/ADHD group, χ2(5) = 13.992, p < .05. About 40.8% of women in the ADD/ADHD group reported personal income below $19,999 compared with 25.8% of men. In addition, 30.3% of men in the ADD/ADHD group reported an income above $40,000 compared with 20.9% of women reporting a diagnosis of ADD/ADHD. Significant differences in marital status were also noted between the ADD/ADHD group and the control group, χ2(4) = 21.24, p < .0001. Compared with the control group, individuals in the ADD/ADHD group less frequently reported being
married but more frequently reported being separated or divorced. Significant gender differences in marital status were observed in the ADD/ADHD group, χ2(4) = 19.657, p = .001, with men more frequently reporting being single.
Comorbid Diagnoses Table 2 shows the frequency with which individuals in the ADD/ADHD and control groups meet criteria for lifetime and current (12-month) psychiatric diagnoses. Significant group differences were found in the frequency of lifetime psychiatric diagnoses with individuals in the ADD/ADHD group meeting criteria for a lifetime diagnosis of all disorders significantly more frequently than individuals in the control group. Individuals in the ADD/ADHD group also
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Hesson and Fowler Table 2. Lifetime Prevalence Rates of Psychiatric Diagnoses in the ADD/ADHD and Control Groups. Frequency, n (%) Psychiatric disorder Lifetime Major depressive disorder Bipolar disorder I Bipolar disorder II Generalized anxiety disorder Alcohol abuse Alcohol dependence Cannabis abuse Cannabis dependence Other drug abuse Other drug dependence 12-month Major depressive disorder Bipolar disorder I Bipolar disorder II Generalized anxiety disorder Alcohol abuse Alcohol dependence Cannabis abuse Cannabis dependence Other drug abuse Other drug dependence
ADD/ADHD (n = 488)
Control (n = 488)
χ2
p
175 (36.0) 31 (6.4) 16 (3.3) 165 (34.0) 127 (26.3) 68 (14.2) 75 (15.5) 42 (8.7) 49 (10.1) 65 (13.5)
61 (12.5) 3 (0.6) 6 (1.2) 47 (9.7) 95 (19.7) 14 (2.9) 35 (7.2) 10 (2.1) 17 (3.5) 14 (2.9)
73.01 24.13 4.757 84.34 5.989 39.37 16.50 20.74 16.72 35.97
