Background

When assessing attention deficit hyperactivity disorder (ADHD), clinicians often use results from neuropsychological tests to obtain objective measures of the patient’s cognitive function to supplement clinical assessments that are based on subjective self-report questionnaires and interviews. There are several reasons for this. The symptoms constituting ADHD are extreme variants of normal behaviours, and the boundary between normality and pathology is based on clinical judgement. Several studies have shown that the diagnosis of ADHD is highly dependent on the source of the report, thus underscoring the need for objective assessments (Barkley, Fischer, Smallish, & Fletcher, 2002). In addition, some symptoms of ADHD may reflect the presence of other disorders. Clinical difficulties related to attention deficits have been confirmed in several studies involving adults with ADHD (Barkley, 2010a; Bush, 2010; Halleland, Haavik, & Lundervold, 2012; Seidman, 2006), and they have been reported in studies assessing the severity of nine Diagnostic and Statistical Manual of Mental Disorders (DSM)-defined inattentive symptoms, for example those reflected in the Adult ADHD Self-Report Scale (ASRS) inattentive subscore (Fredriksen et al., 2014; Kessler et al., 2005; Silverstein et al., 2019). Adults with ADHD also have impaired executive functioning (Silverstein et al., 2020), but they do not necessarily exhibit attention deficits on psychometric tests (Fabio & Caprì, 2017).

Emotional dysregulation, which is recognized as a transdiagnostic factor (Aldao, Gee, De Los, & Seager, 2016), is a common feature in ADHD even though it is not part of the criteria for the disorder (Barkley, 2010b; Barkley & Fischer, 2010; Connor, Steeber, & McBurnett, 2010; Hirsch, Chavanon, Reichmann, & Christiansen, 2018; Landaas, Halmøy, Oedegaard, Fasmer, & Haavik, 2012; Retz, Stieglitz, Corbisiero, Retz-Junginger, & Rösler, 2012; Shaw, Stringaris, Nigg, & Leibenluft, 2014; Surman et al., 2011, 2013). The clinical expression of emotional dysregulation is observable as excessive and inappropriate emotional expressions, irritability, and outbursts of temper (Shaw et al., 2014; Stringaris, 2011). This impulsivity with regard to anger is an important and disabling feature associated with ADHD (Bunford, Evans, & Langberg, 2018; Skirrow & Asherson, 2013). There is a strong relationship between anger and cognitive distortions (Chereji, Pintea, & David, 2012), and frequencies of both the expression of anger and cognitive distortion have been found to be associated with impaired executive functioning (Persampiere, Poole, & Murphy, 2014). Psychometric testing for executive functioning is frequently used in the neuropsychiatric assessment of ADHD, and one core executive function is verbal working memory, which involves the mental retention of auditory information that enables future action (Diamond, 2013). In several studies, a close relationship was found between emotional regulation and the level of working memory (Barkley, 1997; Jasielska et al., 2015; Jensen et al., 2018; Lima, Peckham, & Johnson, 2018; Rutherford, Booth, Crowley, & Mayes, 2016). Emotional dysregulation has not yet been conclusively defined, and there are several ways to measure, interpret, and categorize emotional dysregulation. In our study, emotional dysregulation was assessed based on eight relevant items (see Table 5) from the larger Current Behaviour Scale–Self-Report, known as the Deficient Emotional Self-Regulation (DESR) questionnaire (Barkley, 1997, 2010a; Biederman et al., 2012; Surman et al., 2013). The concept of emotional dysregulation has different aspects, involving both strong emotional responses and the impaired regulation of emotions.

Working memory is an important executive function (Diamond, 2013), and working memory deficits are well documented in adults with ADHD (Alderson, Kasper, Hudec, & Patros, 2013). Psychometric tests of working memory can be used to differentiate between those with and without ADHD in both children and adults (Willcutt, Doyle, Nigg, Faraone, & Pennington, 2015). According to Allan Baddeley, working memory consists of a central executive and two content/modality-specific components: a phonological loop that handles verbal content and a visuospatial sketchpad that handles spatial content (Baddeley & Logie, 1999). Attention deficits/attention control is strongly related to central executive function. In addition, attention deficits in ADHD seem to have a stronger relation to the visuospatial component than to the phonological loop (Faraone & Biederman, 2005; Nigg et al., 2005; Woods, Lovejoy, & Ball, 2002). Different theoretical models have been developed to attempt to gain insight into working memory deficits in ADHD (Barkley, 1997; Diamond, 2005; Rapport, Chung, Shore, & Isaacs, 2001). In our sample, we analysed whether verbal working memory was correlated with the severity of either attention deficits or emotional dysregulation in ADHD.

Psychometric tests of processing speed measure the efficiency of cognitive executive skills, and impairments revealed by such tests have been linked to reports of attention deficits in children with ADHD (Kibby, Vadnais, & Jagger-Rickels, 2019; Thorsen, Meza, Hinshaw, & Lundervold, 2018) and adults with ADHD (Tucha et al., 2017). Impaired processing speed explains to a large extent the impairment in executive functions (Butzbach et al., 2019). Impaired processing speed is linked to inattentive behaviour in children with ADHD (Kubo et al., 2018), and slow processing speed predicts social functioning in ADHD patients with inattention (Thorsen et al., 2018). It seems that slower processing speed and attention deficit coexist and are important predictors of academic achievement (Mayes & Calhoun, 2007). Studies have shown that the WAIS test results can be used to adequately discriminate between adults with and without ADHD, although the intragroup heterogeneity is substantial (Frazier, Demaree, & Youngstrom, 2004; Thaler, Bello, & Etcoff, 2013; Theiling & Petermann, 2014; Woods et al., 2002). Measures of working memory and processing speed can be used to discriminate adequately between ADHD and control groups (Nikolas, Marshall, & Hoelzle, 2019). Deficits in verbal working memory have been reported to be associated with parent-rated emotional dysregulation in children with ADHD (Bunford et al., 2018), but others have not found this association in adults with ADHD (Chereji et al., 2012; Skirrow & Asherson, 2013). In our sample, we measured the correlations between processing speed and the severity of attention deficits and emotional dysregulation in adult ADHD patients. The severity of the symptoms of ADHD is emphasized in the DSM-5 (American Psychiatric Association, 2013), but whether the WAIS test scores are useful as an indicator of the severity of attention deficits and emotional dysregulation is unknown.

We hypothesize that verbal working memory and processing speed are correlated with the severity of attention deficits and emotional dysregulation, even after controlling for covariates. The covariates that may affect the associations between neurocognitive test results and the clinical features of ADHD include age (Ardila, 2007), sex (Rucklidge & Tannock, 2001), education level (Reitan & Wolfson, 1995), and depression (Gorlyn et al., 2006).

The aim of this study was to determine whether the WAIS test results for verbal working memory and processing speed are useful as indicators of the severity of (1) attention deficits and (2) emotional dysregulation in adults with ADHD.

To broaden our understanding of the topic, we also sought to determine whether each item on the attention deficit and emotional dysregulation scales was correlated with the psychometric test results for verbal working memory and processing speed.

Material and methods

This was an observational cross-sectional clinical study.

Participants

The study sample consisted of 418 adults aged 18–65 years who fulfilled the criteria for a diagnosis of attention deficit hyperactivity disorder (ADHD) according to the DSM, Fifth Edition (DSM-5; American Psychiatric Association, 2013). They were referred to a private psychiatric outpatient clinic in Oslo, Norway, that specializes in psychiatric examination, assessment, and treatment of adults with ADHD.

Recruitment was conducted between 2014 and 2018. All patients participating in the study were assessed by a psychiatrist with the semi-structured Diagnostic Interview for ADHD in Adults, second edition (DIVA 2.0; Kooij & Francken, 2010). The DIVA 2.0 is a reliable tool for assessing and diagnosing adult ADHD (Ramos-Quiroga et al., 2019). A clinical diagnosis of ADHD was made according to DSM-5 (American Psychiatric Association, 2013). From 2014 to 2018, 418 of the assessed patients fulfilled the diagnostic criteria for ADHD and were invited to participate in the study. Sixty-five per cent of them were self-referred, and thirty-five per cent had been referred by health care practitioners. All 418 patients (100%) gave their written consent to participate and were included in the study. In accordance with the diagnostic criteria, all participants had ADHD symptoms before the age of 12. At the time of inclusion in study, they had severe ADHD symptoms that resulted in marked impairments in social or occupational functioning. There were no exclusion criteria. None of the participants were under the influence of stimulant medications, alcohol, or other drugs during the clinical assessment or administration of the WAIS test. Comorbid disorders were assessed using the Mini-International Neuropsychiatric Interview (MINI).

The study was approved by the Regional Medical Ethics Committee, South-East Norway 2015/426. Assessments and the handling of data were carried out in accordance with the relevant ethics standards and the principles of the Declaration of Helsinki.

Measures

The age of the participants was recorded in years at the time of enrolment. Sex was recorded as female (scored as 0) or male (scored as 1) based on patient self-report. The following sociodemographic information was collected. Marriage or cohabitation was scored as 1, and all other statuses were scored as 0. If the participant was living with children of whom they had at least partial custody, a score of 1 was recorded; otherwise, even if they had no children, or children who lived somewhere else, a score of 0 was recorded. Education level was categorized by the number of years of education as follows: 12 years or fewer was scored as 1, 13–15 years was scored as 2, and more than 15 years was scored as 3. Employment was defined as ‘yes’ and scored as 1 if that employment was reported as the main source of income; otherwise, it was scored as 0.

The level of depression was measured by the Montgomery–Åsberg depression rating scale (MADRS), with all ten items summarized as a total score ranging from 0 to 60 (Montgomery & Åsberg, 1979). The MADRS is a reliable and valid screening instrument for the evaluation of depression (Davidson, Turnbull, Strickland, Miller, & Graves, 1986).

ADHD symptom severity was measured using the Adult ADHD Self-Report Scale (ASRS) Symptom Check List, v1.1 produced by the World Health Organization (World Health Organization, 2003). The ASRS is a reliable and valid screening instrument for the evaluation of ADHD in adults (Fredriksen et al., 2014; Kessler et al., 2005; Silverstein et al., 2019). The ASRS questionnaire is composed of 9 attention deficit items (items 1–4 and 7–11) and 9 hyperactive-impulsive items (items 5, 6, and 12–18; Fredriksen et al., 2014). Response options for each item range from 0 to 4. The items were marked by the participant as never (0), rarely (1), sometimes (2), often (3), and very often (4). This yielded a total attention deficit score ranging from 0 to 36 (see Table 4).

Emotional dysregulation was assessed with a questionnaire containing eight items from the 99 items on the Current Behaviour Scale–Self-Report (CBS-SR) questionnaire, known as the DESR scale (Barkley, 1997, 2010b; Barkley & Fischer, 2010; Biederman et al., 2008; Surman et al., 2013). The eight items were as follows: 1: Quick to get angry or become upset; 2: Easily frustrated; 3: Overreact emotionally; 4: Easily excited by activities going on around me; 5: Lose my temper; 6: Argue with others; 7: Am touchy or easily annoyed by others; and 8: Am angry or resentful. The eight items are described in Table 5, and their response options range from 0 to 3. The items were marked by the participant as never or rarely (0), sometimes (1), often (2), and very often (3). This yielded a total ED score ranging from 0 to 24 (see Table 5).

Verbal working memory was assessed by the Working Memory Index (WMI; tests of Arithmetic, Digit Span and Letter-Number Sequencing), and processing speed was assessed with the Processing Speed Index (PSI; tests of Digit Symbol-Coding, Symbol Search) from the Wechsler Adult Intelligence Scale, 3rd edition (WAIS-III).( Evers et al., 2012; Kaufman, 1999; Wechsler, 1997; Wechsler, Nyman, & Nordvik, 2003) The test scores included in the statistical analyses were the age-corrected scale scores.

Procedure

The data were collected during routine assessments performed by a psychiatrist in an outpatient clinic. Psychometric testing was completed by a special education teacher with experience and expertise in ADHD and the use of the WAIS-III.

After the assessment, the patients were asked if they approved the use of their clinical information in an anonymous form in the statistical analyses for this clinical trial.

Statistical analysis

Frequencies with per cent proportions are reported for all categorical variables and means with standard deviations are reported for continuous descriptive variables. We performed chi-square tests or t-tests to compare sociodemographic characteristics between females and males. All tests were two-tailed, and differences were considered significant if p < .05. Continuity correction was performed, and Asymp. Sig. (2-sided) was recorded. t Tests were used to compare continuous variables between females and males.

We used linear regression analyses to examine associations between measures of self-reported attention deficit (the ASRS subscore), or self-reported emotional dysregulation (the DESR scale) as the dependent/outcome variables, and sociodemographic variables, the MADRS score, the Working Memory Index (WMI) and the Processing Speed Index (PSI) as the independent variables. The test scores from the WAIS-III included in the statistical analyses were the age-corrected scale scores. We used Cronbach’s alpha to assess the internal consistency and reliability of the eight items from the DESR scale. Cronbach’s alpha for the eight scale items in our sample was .86, indicating high internal consistency.

Given our two hypotheses, we used the Bonferroni correction and considered differences significant if p was < .025. For all association tests, beta ratios with 95% confidence intervals were calculated as the measurement of the effect size. To measure the explained variance, we used the R2-squared value. If the R2 value was <.30, the effect was considered weak. If the R2 value was between .30 and .50, the effect was considered moderate. If the R2 value was >.50, the effect was considered strong (Moore, Notz, & Notz, 2006).

We used Pearson correlation analyses to examine the associations of each of the nine attention deficit items on the ASRS and each of the eight emotional dysregulation items on the DESR scale with the Working Memory Index (WMI) and the Processing Speed Index (PSI).

There were no missing data. All statistical analyses were performed using IBM SPSS version 22 (IBM, 2013).

Results

Table 1 shows the demographics, depression severity (as the MADRS score), attention deficit ASRS subscale score, hyperactive-impulsive ASRS subscale score, total WAIS score, and four WAIS subindex scores in the females (n = 188) and males (n = 230) in this study. More females than males lived with children. A total of 61.7% of the participants reported employment as their main source of income, and nearly 51.4% reported that they had received more than 12 years of education. The frequencies of psychiatric comorbidities in this sample were 12.9% for depressive disorders, 31.8% for anxiety disorders, and 13.6% for substance use disorders.

Table 1. Demographic characteristics, depression (MADRS score), ASRS scores measuring attention deficits and hyperactivity-impulsivity separately, emotional dysregulation measured by the Deficient Emotional Self-Regulation (DESR) scale and WAIS scores with four subindex scores, in 418 adult patients diagnosed with ADHD in a psychiatric outpatient clinic specializing in the examination and treatment of ADHD All (n = 418) Male (n = 230) Female (n = 188) Age range 18–69 18–67 18–69 Age: mean (SD) 36.6 (11.5) 36.1 (11.8) 37.2 (11.1) Education years (%) ≤12 203 (48.6) 122 (53.0) 81 (43.1) 13–15 179 (42.8) 92 (40.0) 87 (48.6) >15 36 (8.6) 16 (7.0) 20 (10.6) Married/cohabiting 188 (45.0) 105 (45.7) 83 (44.1) Living with children 178 (42.6) 86 (37.4) 92 (48.9)* Employment 258 (61.7) 149 (64.8) 109 (58.0)* Depression-MADRS score, mean (SD) 12.4 (6.4) 12.4 (6.9) 12.4 (5.7) Comorbidity Depressive disorders (%) 54 (12.9) 28 (12.2) 26 (13.8) Anxiety disorders (%) 133 (31.8) 58 (25.2) 75 (39.9)** Substance use disorders (%) 57 (13.6) 36 (15.7) 21 (11.2) ASRS: Attention deficit score, mean (SD) 27.3 (4.4) 26.9 (4.4) 27.8 (4.2)* ASRS: Hyperactivity-impulsivity score, mean (SD) 23.8 (6.5) 23.1 (6.7) 24.6 (6.3)* Emotional dysregulation score, mean (SD) 12.1 (5.5) 11.0 (5.6) 13.4 (5.0)*** WAIS total score: FSIQ Mean (SD) 103.2 (13.8) 104.8 (13.5) 101.3 (14.0)** Range 66–151 71–151 66–145 Verbal Comprehension Index Mean (SD) 105.9 (12.7) 107.2 (12.6) 104.2 (12.7)** Range 74–161 82–150 74–145 Perceptual Organizational Index Mean (SD) 110.5 (16.0) 111.6 (15.8) 109.2 (16.2) Range 70–150 70–150 72–148 Working Memory Index (WMI) Mean (SD) 90.5 (13.1) 92.3 (12.3) 88.2 (13.1)** Range 57–136 65–136 57–126 Processing Speed Index (PSI) Mean (SD) 88.1 (12.5) 88.3 (12.7) 87.2 (12.3) Range 57–125 60–125 57–120 Note Numbers (percentage) or means (standard deviation) are reported. Sexes are compared with the chi-squared test or t-test. * p < .05. ** p < .01. *** p < .001. (Females compared with males.)

The mean hyperactive-impulsive score (SD), mean attention deficit score (SD), and mean emotional dysregulation score (SD) are reported. Females in our sample scored higher on all three measures. The table also shows the WAIS profile of our sample. The mean full-scale intelligence quotient (FSIQ) in our sample was 103.2 (SD: 13.8), and females had an average FSIQ of 101.3, while men had an average FSIQ of 104.8. Both sexes had typical profiles with significantly reduced scores on the Working Memory Index (WMI) and Processing Speed Index (PSI) compared to those expected based on their FSIQ. Significant correlations (p < .001) were found between all four subindex scores on the WAIS (data not shown).

The severity of attention deficits, as reflected in the ASRS attention deficit subscale score, was significantly correlated only with the PSI (Pearson correlation −.16, p < .001).

The severity of hyperactivity and impulsivity, as measured by the ASRS hyperactivity-impulsivity subscale, was significantly correlated with the FSIQ (Pearson correlation −.19, p < .001) and all four subindex scores but was not associated with any of the independent variables in the adjusted model (data not shown).

The severity of emotional dysregulation, as measured by the DESR scale score, was significantly correlated with the FSIQ (Pearson correlation −.23, p < .001) and with all four subindex scores.

Table 2 shows the linear regression model of the associations between the outcome/dependent variable attention deficit severity, as measured by the ASRS inattention subscore, and the independent variables of age, sex, education level, depression, the WMI, and the PSI. The PSI (β = −.056, CI −0.094 to −0.017, p = .005) but not the WMI (β = −.012, CI: −0.049 to 0.025, p = .52) was associated with attention deficits. The R square (explained variance) for the fully adjusted model was .026, that is the model explained only 2.6% of the variance in attention deficits in our sample. None of the covariates were significantly associated.

Table 2. Associations between attention deficits measured by the ASRS inattention subscore as an outcome/dependent variable and age, sex, education level, depression measured by the MADRS score, Working Memory Index (WMI) and Processing Speed Index (PSI) as independent variables in a clinical sample of 418 adult ADHD patients. Linear regression Unadjusted Adjusted B 95% CI p-Value R 2 B 95% CI p-Value R 2 Age .002 −0.039 to 0.034 .910 −.002 −.003 −0.039 to 0.034 .882 .026 Sex (male vs. female) −.922 −1.76 to −0.082 .031 .009 −.781 −1.635 to 0.073 .073 Education (3 level) .164 −0.49 to 0.82 .621 −.002 .520 −0.188 to 1.229 .150 Depression (MADRS score) .003 −0.063 to 0.069 .929 −.002 −.001 −0.067 to 0.064 .965 Working Memory Index −.035 −0.067 to 0.003 .033 .009 −.012 −0.049 to 0.025 .524 Processing Speed Index −.054 −0.087 to −0.021 .002 .021 −.056 −0.094 to −0.017 .005

Table 3 shows the linear regression model of the associations between the severity of emotional dysregulation, as measured by the DESR scale, as the outcome/dependent variable and the independent variables of age, sex, education level, depression, the WMI and the PSI. Neither the WMI (β = −.05, CI: −0.095 to −0.002, p = .041) nor the PSI (β = −.03, CI: −0.08 to −0.13 p = .22) were associated with the severity of emotional dysregulation in the adjusted model after the Bonferroni correction, with significance based on p < .025. Depression was associated with the severity of emotional dysregulation (β = .13, 95% CI: 0.05–0.21, p = .002). The R-squared value (explained variance) for the fully adjusted model was .098, that is the model explained only 9.8% of the variance in emotional dysregulation in our sample. Age and education level did not contribute to the explained variance, but being female was significantly associated with emotional dysregulation (β = −2.13, 95% CI: −3.18 to −1.09, p < .001), and depression was also significantly associated with emotional dysregulation (β = .13, 95% CI: 0.05–0.21, p = .002).

Table 3. Associations between emotional dysregulation measured by the Deficient Emotional Self-Regulation (DESR) scale as an outcome/dependent variable and age, sex, education level, depression (MADRS score), Working Memory Index (WMI) and Processing Speed Index (PSI) as independent variables in a clinical sample of 418 adult ADHD patients. Linear regression Unadjusted/crude Adjusted B 95% CI p-Value R 2 B 95% CI p-Value R 2 Age .018 −0.03 to 0.06 .43 .001 .021 −0.02 to 0.066 .35 .098 Sex (male vs. female) −2.36 −3.40 to −1.32 <.001 .046 −2.13 −3.18 to −1.09 <.001 Education (3 level) −.61 −1.44 to 0.22 .15 .005 −.16 −1.03 to 0.71 .72 Depression (MADRS score) .14 0.06 to 0.23 .001 .026 .13 0.05 to 0.21 .002 Working Memory Index −.08 −0.12 to −0.040 <.001 .035 −.05 −0.095 to −0.002 .041 Processing Speed Index −.058 −0.10 to −0.016 .007 .017 −.03 −0.08 to −0.13 .22

Table 4 shows the nine attention deficit items in the DSM-5 ADHD criteria and the nine corresponding inattentive items on the ASRS, the Pearson correlations with the WMI and PSI and the significance (2-tailed). Four items pertaining to attention deficits were correlated with the WMI (ASRS items 1, 3, 7, and 9), and four items were correlated with the PSI (ASRS items 2, 3, 9, and 11). Three items were correlated with neither (ASRS items 4, 8, and 10).

Table 4. DSM-5 ADHD criteria: nine items pertaining to attention deficits, the corresponding nine ASRS inattentive items and their correlations with the Working Memory Index (WMI) and Processing Speed Index (PSI) in a clinical sample of 418 adult patients with ADHD