Exploring the relationship between ADHD, its common comorbidities, and their relationship to organizational skills

Introduction

The DSM-V lists attention deficit hyperactivity disorder (ADHD) as a neurodevelopmental disorder that causes significant impairments in the areas of attention, hyperactivity, and impulsivity. ADHD can be divided into three subtypes based on severity: inattentive presentation (ADHD-I), hyperactive-impulsive presentation (ADHD-HI), or combined presentation (ADHD-C; American Psychiatric Association, 2013). Worldwide, the prevalence of ADHD in adults 18 to 44 years old is between 1.1% and 7.3% (Fayyad et al., 2007).

Results

All analyses were performed by condition (no-ADHD/ADHD). The attribution to one group or the other (no-ADHD/ADHD) was based on the participant’s response to having received (or not) a diagnosis of ADHD from a health professional (physician, psychiatrist, or psychologist). Examination of Kurtosis and Skewness support a normal distribution on the DOSQ and its subscales, alongside the ASRS, the PHQ, and the STAI-6. Table 1 shows the descriptive data (mean, standard deviation, assumptions of normality and Cronbach’s alpha) for both conditions, as well as the Cohen’s d effect size on each scale between condition for all self-reported instruments in the present study. A series of analysis of variance (ANOVA) supported mean differences between conditions on the DOSQ Total (F(1, 405) = 50.638, p < .001), alongside most of its subscales: Work Organization (F(1, 405) = 23.474, p < .001), Communication Clarity (F(1, 405) = 28.208, p < .001), Punctuality (F(1, 405) = 31.946, p < .001), Assiduity (F(1, 405) = 103.410, p < .001), and Attentiveness (F(1, 405) = 103.464, p < .001). Differences were also observed on both ASRS scales, namely Inattention (F(1, 405) = 140.400, p < .001) and Hyperactivity-Impulsivity (F(1, 405) = 92.451, p < .001). Table 2 provides additional descriptive data specifically related to individuals with a diagnosis of ADHD in terms of taking medication, time since the diagnosis, and seeking therapy.

Chi-square tests were performed between groups on six independent variables, namely education, biological sex, depression level, anxiety level, ADHD level, and comorbid diagnoses, and are reported in Table 3. For comorbid diagnoses, participants answered the question “Do you have (or have you received in the past) a diagnosis for […] from a physician, a psychiatrist, or a psychologist?”. Overall, individuals with a diagnosis of ADHD had a higher likelihood of being female and having a diagnosis of depression or anxiety, as well as having higher levels of self-reported ADHD symptoms. However, the analysis did not support a difference between the groups in terms of the intensity of self-reported depressive symptoms and anxiety. Individuals without ADHD had a higher likelihood of never having received a diagnosis for a mental illness.

Subsequently, we examined the difference in organizational skills in terms of diagnoses and self-reported information related to ADHD, depression, and anxiety. To correct for multiple testing, a Bonferroni correction of p = .05/6 = .008 was applied to account for the six analyses. A series of ANOVAs confirmed that lower levels of organizational skills were present in individuals who received a diagnosis of ADHD (as mentioned in Table 1), but not in individuals who received a diagnosis (at some point in their past) of depression (F(1, 405) = 5.524, p = .019, d = 0.23) or anxiety (F(1, 405) = 6.860, p = .009, d = 0.26). Furthermore, lower levels of organizational skills were observed in individuals passing the threshold value on the ASRS (F(1, 405) = 201.535, p < .001, d = 1.48) and the PHQ (F(1, 405) = 25.053, p < .001, d = 0.52), as well as those above the mean on the STAI-6 (F(1, 405) = 22.785, p < .001, d = 0.47).

Lastly, we performed two regression analysis, one per group of ADHD diagnosis, to identify other variables measuring organizational skills. For individuals with a diagnosis of ADHD, a stepwise regression model was computed with the following variables: depression diagnosis, anxiety diagnosis, no diagnosis, sex, age, PHQ total, ASRS inattention total, ASRS hyper-impulsivity total, STAI-6 total, medication, and therapy. The results suggested a significant model (F(3, 197) = 38.324, p < .001, adjusted R² = .36). The only significant predictors were ASRS inattention (Standardized B = −0.532, t =  − 8.552, p < .001), ASRS hyper-impulsivity (Standardized B = 0.158, t = 2.548, p < .001) and self-reported depression total (Standardized B = −0.263, t =  − 4.380, p < .001). The first model, containing only inattention, explained 29% of the variance, increasing to 34% when also taking into account self-reported depression and 36% when also including hyperactivity-impulsivity.

A second regression analysis was performed for individuals without a diagnosis of ADHD with the aforementioned predictors, aside of medication and therapy. The results suggested a significant model (F(5, 199) = 88.503, p < .001, adjusted R² = .68). The significant predictors included sex (Standardized B = 0.145, t = 3.582, p < .001), anxiety diagnosis (Standardized B = 0.145, t = 3.445, p = .001), ASRS inattention (Standardized B = −0.818, t =  − 16.108, p < .001), ASRS hyper-impulsivity (Standardized B = 0.131, t = 2.842, p = .005), and self-reported depression total (Standardized B = −0.138, t =  − 2.888, p = .004). The first model, containing only inattention, explained 62% of the variance. The variance explained increased to 65% when also including sex, 66% when adding anxiety diagnosis, 67% when including self-reported depressive symptoms, and 68% when adding hyperactivity-impulsivity.

Discussion

This study examined the relationship between ADHD and comorbid disorders, as well as their relationship with organizational skills. As expected, the results suggest that people with ADHD are more likely to have a comorbid diagnosis of depression (p < .001) or anxiety (p < .001). This finding is aligned with the literature, as previous results suggest that individuals with ADHD are five time more likely to have a diagnosis of depression than individuals without ADHD (Angold, Costello & Erkanli, 1999). Although associations between anxiety and ADHD vary considerably (Busch et al., 2002; Jensen et al., 2001a; Jensen et al., 2001b), findings suggest that 20% of individuals with ADHD are diagnosed with anxiety (Jarrett & Ollendick, 2008). Furthermore, the present study highlights a difference in psychiatric symptoms among the groups with/without ADHD, as half of the people with no ADHD reported having never received a diagnosis for a mental health issue, as opposed to only 16% for those with ADHD (excluding ADHD itself) (p < .001).

Interestingly, no significant difference was found when comparing groups of low and high levels of depression and anxiety. The discrepancy could be caused by the timeframe of the symptoms. For the diagnosis, individuals may have a current depression/anxiety disorder, or may have had one in the past that was eventually treated. However, self-reported instruments were referring to current (within the past few weeks) symptoms associated with depression and anxiety. The similar ratio of self-reported anxiety and depression in individuals with and without ADHD could be due to the large proportion of students in the sample size. Multiple studies suggest that university students display high levels of depressive and anxiety-related symptoms (Bayram & Bilgel, 2008; Eisenberg, Golberstein & Hefner, 2007). As expected, individuals with a diagnosis of ADHD were more likely to obtain a high score on the ASRS, while individuals without a diagnosis were more evenly distributed between low and high scores on the ASRS. There are two potential explanations for these results. First, the study was advertised as a study focusing on ADHD. It is possible that individuals who suspect they have ADHD may have been disproportionately more interested in participating in this study. Secondly, multiple studies suggest that many adults are not properly diagnosed once they reach adulthood, and that the majority of those undiagnosed individuals remain untreated (Montejano et al., 2011).

Our findings also suggest that individuals with a diagnosis of ADHD, as well as individuals with higher levels of self-reported depression, anxiety, and stress, display lower levels of organizational skills. Interestingly, this difference was not found for individuals with a current or past diagnosis of depression or anxiety disorder. As previously mentioned, these results may be due to the focus of self-reported instruments on current symptoms. Multiple studies suggest that anxiety and depression negatively impact executive functions concurrently (O’Rourke EJ & Vaysman, 2020; Rabin, Fogel & Nutter-Upham, 2011) or years in the future (Zainal & Newman, 2022). It is possible that individuals who currently experience symptoms associated to depression and anxiety experience a decline in executive functions, such as organizational skills. It is however unknown if there is a cause and effect or if it is simply a relationship. It is also currently unknown if these lower levels of organizational skills are temporary or permanent. Nevertheless, these results suggest that while common comorbid diagnosis of ADHD may play a role in reduced organizational skills, their contribution may not be as impactful as ADHD, considering the large difference in effect sizes between ADHD and self-reported anxiety and depression in relation to organizational skills.

In the present study, two regression analyses were computed to examine the significant predictors of organizational skills. The results suggested that, for both individuals with and without ADHD, the inattention component of the ASRS was the strongest predictor to measure organizational skills, assessing 29% and 62% of the variance for individuals with and without ADHD, respectively. Additional predictors, while statistically significant, were marginal, increasing the total variance by only 7% and 6%, respectively. These results confirm the centrality of the inattention factor in a reduction of organizational skills (Bikic et al., 2017). It is possible that, while other factors may impact the severity of ADHD as a disorder (such as comorbid disorders, sex, etc.), the inattention component has the strongest impact on reduced executive functioning, such as organizational skills. Future studies should explore the difference in individuals with and without the hyperactivity-impulsivity component of ADHD in order to further explore the role of the inattention component on organizational skills.

Conclusion

The findings of this study suggest that organizational skills are a core facet of ADHD, weakly related to other comorbid disorders the individual with ADHD may be experiencing. The findings support the study’s hypotheses: individuals with ADHD are more likely to have or have received at some point a diagnosis of anxiety disorder or depression, organizational skills are lower in individuals reporting higher levels of symptoms of ADHD, depression, and anxiety, and regression analyses suggest that inattention is the largest predictor of organizational skills in individuals with and without ADHD.

Future studies should also explore the utility of therapies focused on increasing organizational skills in individuals with ADHD. The development of such interventions is particularly important, given that problems with organizational difficulties are likely to persist even when other ADHD symptoms lessen (Murphy et al., 2018), and given the contribution of organizational skills to functional and educational success (Barkley, 2014; Cantwell & Baker, 1991; Frick et al., 1991; Pastor & Reuben, 2002). Despite these findings, the present study has a few limitations, including a lack of employment-related information (managerial positions, success, job satisfaction), and a relatively small sample (N = 407) which may have prevented finding cases with rare diseases (e.g., other common comorbid disorders to ADHD such as sleep disorders). It was also noted that the current study was possibly too long for those individuals with very severe ADHD. Therefore, it is recommended that future studies be shorter or be delivered in multi-steps. Additionally, the present study did not distinguish between current and past diagnosis of depression and anxiety. While a lack of distinction is less problematic for life-long pathologies (such as bipolar disorder), it is highly possible that some individuals were diagnosed in the past for depression or anxiety but are not currently experiencing symptoms. Future studies should take these cases into account when assessing comorbid disorders. Lastly, the participants included in the sample may not be an adequate representation of the general population. A large proportion of the sample included females with high levels of education. This could be due to some of the recruitment method, which focused on online support groups for ADHD. Future studies should attempt to recruit from the general population while keeping a better ratio between males and females.

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