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2 Oct 2020

Bozhilova S et al. J Atten Disord 2020; Epub ahead of print

Clinical observation suggests adults with ADHD have poorly controlled and excessive mind wandering (MW) (Asherson, 2005). It has not been determined whether an individual with ADHD is MW or focused on a task with an experimental experience sampling approach using thought probes. It has been proposed that deficient context regulation of neural activity may underlie poor context regulation of MW in ADHD (Bozhilova et al, 2018). Context regulation enables a task to be performed optimally, which occurs when MW frequency decreases as the task demands increase (Smallwood & Andrews-Hanna, 2013). The first aim of the current study was to examine the association between experience sampling measures of MW and clinical measures of MW, ADHD, executive skills and functional impairment. The second aim of the study was to examine the frequency of MW during changing task demands and context regulation in individuals with ADHD compared with individuals without ADHD. The third aim was to determine whether MW was able to statistically explain any between-group differences by comparing the cognitive performance between ADHD and non-ADHD individuals.

The participants were invited for a 3–4-hour long test session that included a diagnostic interview for ADHD, a cognitive task battery that comprised two tasks, IQ testing and self-report questionnaires. The first cognitive task was a MW task (MWT) that involved a 0-back (choice reaction) condition that measured motor speed and general alertness, as well as a 1-back condition that measured an individual’s visual working memory performance. The MWT has previously been shown to demonstrate context regulation of MW in population-based samples (Konishi et al, 2015). The second cognitive task was a sustained attention task (SAT), which was a vigilance task whereby there were three levels in which the sustained attention load was progressively increased (2, 5 and 8 seconds). The level of MW was recorded using MW thought probes (15 per session; 30 in total) at 1-minute intervals throughout the tasks. Cognitive performance was measured using intra-subject reaction time variability, mean reaction time and error rate.

In total, 56 individuals (n = 27 with ADHD; n = 29 non-ADHD) participated in the study. There was no significant difference between the proportion of males and females included in each group (ADHD, 16:11; non-ADHD, 14:15; p = 0.29). The mean (standard deviation [SD]) age of included participants was also similar (ADHD, 37 [8.67] years; non-ADHD, 32 [11.42] years; p = 0.06).

Associations between experimental MW frequency and ADHD and MW rating scale measures

ADHD symptoms, spontaneous MW, executive function and functional impairment were positively associated with the frequency of MW during the MWT and SAT (p < 0.0001 for each). Deliberate MW was not correlated with the frequency of MW during MWT and SAT (p = 0.13 and p = 0.29, respectively). Participants with ADHD reported significantly higher overall mean (SD) MW frequency compared with non-ADHD participants on the MW Excessively Scale (27.78 [7.19] vs 5.31 [5.26]; p < 0.001) and the Spontaneous MW Scale (24.37 [3.47] vs 12.58 [5.91]; p < 0.001). Mean (SD) MW frequency was not different on the Deliberate MW Scale when participants with ADHD were compared with non-ADHD participants (17.52 [7.51] vs 15.69 [6.47]; p = 0.33).

MW frequency and context regulation of MW during the MWT and SAT

MW frequency during the MWT was significantly different between individuals with and without ADHD (p = 0.026). It was noted during post hoc analysis of the context regulation tasks that there was more frequent MW during the 0-back compared with the 1-back condition (p = 0.001) among the individuals with ADHD, but not among non-ADHD participants. Those with ADHD exhibited more delays during the SAT versus non-ADHD individuals (p = 0.02). In individuals with ADHD, there was more frequent MW during the 5-second (p = 0.02) and 8-second delay (p = 0.04) compared with the 2-second delay, but there was no significant difference between 5-second and 8-second delay (p = 0.58). In contrast, the MW frequency of the non-ADHD individuals was not significantly changed by increasing delays (2 second vs 5 second, p = 0.982; 2 second vs 8 second, p = 0.177; 5 second vs 8 second, p = 0.07).

Cognitive performance and the moderating effect of MW frequency

During the MW task, all participants were slower at the 1-back condition compared with the 0-back condition. However, after adding MW frequency as a covariate, individuals with ADHD were slower overall compared with non-ADHD individuals (p = 0.013). Also, individuals with ADHD had more variable reaction time responses than non-ADHD participants when MW frequency was added as a covariate (p = 0.03). Additionally, individuals with ADHD had a higher error rate in the 1-back compared with the 0-back (p = 0.001) condition. However, this was no longer significant after adding MW frequency as a covariate (p = 0.68). During the SAT, individuals with ADHD had overall slower responses with increasing delays (1 second vs 2 second, p < 0.001; 1 second vs 5 second, p < 0.001; 1 second vs 8 second, p < 0.001; 2 second vs 5 second, p = 0.005; 2 second vs 8 second, p < 0.001; 5 second vs 8 second, p = 0.043). After adding MW frequency as a covariate, both the group effect (p = 0.048) and condition-by-group effect (p = 0.0451) were no longer significant. There were more omission errors associated with individuals with ADHD compared with non-ADHD individuals after adding MW frequency as a covariate (p = 0.01). Overall, the ADHD group made more variable responses following more frequent 1-second delays. In addition, compared with non-ADHD individuals, individuals with ADHD made more omission errors during the SAT.

There were three main limitations of this study. Firstly, the sample size was small, meaning that only medium-to-large effects could be detected as significant. Secondly, the authors used differences in error rate only as a proxy of working memory capacity, therefore limiting interpretation. Thirdly, the tasks were not sufficiently difficult for the non-ADHD individuals.

The authors noted that there was a strong association between experimentally derived measures of MW frequency with ADHD symptoms, executive function, functional impairment in daily life and spontaneous MW. These findings confirm the translational value of experimentally derived measures of MW frequency as predictors of clinical outcomes and as possible treatment targets for ADHD. In summary, individuals with ADHD displayed context regulation of MW frequency in response to increases in working memory load, but not in response to increasing sustained attention load. A deficiency in context regulation of MW during increasing demands on sustained attention may reflect a core process of ADHD, which may have implications for neurocognitive models of ADHD and MW.

Read more about regulation of mind wandering in ADHD here

Asherson P. Clinical assessment and treatment of attention deficit hyperactivity disorder in adults. Expert Rev Neurother 2005; 5: 525-539.

Bozhilova N, Michelini G, Jones C, et al. Context regulation of mind wandering in ADHD. J Atten Disord 2020; Epub ahead of print.

Bozhilova NS, Michelini G, Kuntsi J, et al. Mind wandering perspective on attention-deficit/hyperactivity disorder. Neurosci Biobehav Rev 2018; 92:464-476.

Smallwood J, Andrews-Hanna J. Not all minds that wander are lost: the importance of a balanced perspective on the mind-wandering state. Front Psychol 2013; 4: 441.

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