Few of them write how an architect builds, who has already drawn up a plan and thought it through in detail; rather most of them just like to play dominoes.
— Arthur Schopenhauer
There’s no single test to diagnose ADHD. Instead, psychiatrists rely on several things, including:
- Interviews with the parents, relatives, teachers, or other adults
- Personally watching the child or adult
- Questionnaires or rating scales that measure of ADHD
- Neurocognitive tests
Several neurocognitive tests have been developed for research in ADHD, as well as auxiliary instruments for diagnosis and assessment of treatment efficacy in children and adults with ADHD. Usually, the psychiatrist gets ADHD assessments from the parents, teacher or supervisor. Some common rating scales include:
The Vanderbilt Assessment Scale – reviews symptoms of ADHD according to the DSM-V criteria. It also screens for co-existing conditions such as behavioral disorder, oppositional-defiant disorder, anxiety, and depression.
- The Child Behavior Checklist (CBCL) is a component of the Achenbach System of Empirically Based Assessment (ASEBA). The ASEBA is used to detect behavioural and emotional problems in children and adolescents. The CBCL is completed by parents.
- The other two components are the Teacher’s Report Form (TRF) (completed by teachers), and the Youth Self-Report (YSR) (completed by the child or adolescent himself or herself). The 2001 revision of the CBCL, the CBCL/6-18 (used with children 6 to 18), is made up of eight syndrome scales: • anxious/depressed • depressed • somatic complaints • social problems • thought problems • attention problems • rule-breaking behaviour • aggressive behaviour. These group into two higher order factors—internalizing and externalizing. The time frame for item responses is the past six months. The 2001 revision also added six DSM-oriented scales consistent with DSM diagnostic categories: • affective problems • anxiety problems • somatic problems • ADHD • oppositional defiant problems • conduct problems.
When developing computerized cognitive tasks, researchers base their tools on the hypothesized impaired cognitive function that they demand. ADHD tests usually focus on the evaluation of executive functions and working memory (Gallagher & Blader, 2001; Willcutt, Doyle, Nigg, Faraone, & Pennington, 2005). However, heterogeneity exists between tools that allegedly examine similar cognitive functions. This heterogeneity might contribute to the complexity of generalizing concepts from findings of different studies. Meta-analyses and reviews show that executive function processes demonstrate considerable variability in ADHD samples, with only a proportion of participants with ADHD displaying impairment in one or more of these measures (Nigg, Willcutt, Doyle, & Sonuga-Barke, 2005; Willcutt et al., 2005). In addition, different executive functions (EFs) tend to correlate with one another. For example, Freedman et al. have shown substantial correlations among three EF latent variables (updating, shifting, and inhibition; Friedman, Miyake, Robinson, & Hewitt, 2011). Therefore, differences between testing tools might have an important ramification when trying to integrate or compare results from different studies assessing similar cognitive functions (Corkum & Siegel, 1993; Nigg, 2005).
Several laboratory tests have been developed to assess continuous performance, one of the key cognitive domains known to be impaired in ADHD (Seidman et al., 2004; Willcutt et al., 2005). The basic paradigm of a continuous performance test (CPT) involves selective attention or vigilance for an infrequently occurring stimulus (Eliason & Richman, 1987). CPTs are generally characterized by rapid presentation of continuously changing stimuli among which there is a designated “target” stimulus or pattern. The duration of the tasks varies, but all are intended to be of sufficient length to measure sustained attention. Various components of the CPT tasks have been found to be associated with altered dopaminergic functioning in the mesolimbic cortical branch (Huang-Pollock, Karalunas, Tam, & Moore, 2012).
For many years, the CPT has been used in the study of attention, as well as impulsivity, with consistent findings of sensitivity to central nervous system dysfunction (Riccio, Waldrop, Reynolds, & Lowe, 2001). However, extensive variations in CPT paradigms exist (HuangPollock et al., 2012; Riccio, Reynolds, Lowe, & Moore, 2002). For example, different CPT tasks include varying amounts of target stimuli. Also, some tasks require the identification of a single stimulus (i.e., the Test of Variables of Attention [TOVA]; Greenberg & Waldman, 1993), while others require identification of a sequence of stimuli (i.e., the Rapid Visual Processing [RVP] test; Gau & Huang, 2014). Variations in CPT types may affect the level of their sensitivity. The abundance of variations in task parameters as well as CPT demands makes generalization of performance data difficult, particularly with regard to attentional asymmetry (Riccio et al., 2001). Furthermore, the large number of CPT versions is a vexing disadvantage when trying to quantitatively synthesize data from different studies (e.g., through meta-analysis). Despite the extensive literature concerning CPTs in children and adults with ADHD, no study to date has examined the relative sensitivity of different CPT tasks or score types.
In addition to the CPT, other tests measure response inhibition, another fundamental executive control process that comes into play in situations requiring withholding, switching, or suddenly interrupting ongoing actions and thoughts (Doyle, 2006). Deficient inhibitory control is mainly a result of frontal or prefrontal lobe dysfunction (Homack & Riccio, 2004), and is a well-replicated finding in children and adults with ADHD (Oosterlaan, Logan, & Sergeant, 1998; Schachar, Mota, Logan, Tannock, & Klim, 2000; Seidman et al., 2004; Willcutt et al., 2005). The Stroop inhibitory control was found in a number of studies (Barkley, 1997a; Soreni, Crosbie, Ickowicz, & Schachar, 2009) but not all (Schwartz & Verhaeghen, 2008; van Mourik, Oosterlaan, & Sergeant, 2005), to reflect impairments in response inhibition in individuals with ADHD.