4. Attention Deficit Hyperactivity Disorder
1. Characteristics of ADHD
o ADHD is defined on the basis of 2 dimensions:
Inattention
Hyperactivity/impulsivity
o So not all children with ADHD are hyperactive!
o These two dimensions result in 3 subtypes of ADHD:
1) Hyperactive/impulsive (HYP)
2) Inattentive (INATT)
3) Combined – most common
o Interesting note about prevalence:
o More males than females (3:1 community sample; 9:1 referred sample; Taylor,2006) BUT
o Girls are more likely to have INATT and/or be less disruptive and/or be less likely to have co-occurring
conditions (Biederman et al., 2005).
o Factors: Genetics, Dopamine Dysregulation, Environmental Factors (diet, birth etc.)
o Behaviours
Inattention (ADD): Hyperactivity:
- Often fails to pay attention to details & - Restless, fidgets with hands or feet, or
makes careless mistakes squirms in seat
- Often has difficulty sustaining - Often leaves seat in classroom
attention - Runs or climbs excessively when quiet
- Doesn’t seem to listen when spoken to behaviour is expected
- Rarely follows through on instructions - Difficulty planning or engaging in
& fails to finish work leisure activities quietly
- Difficulty organising tasks - Often ‘on the go’ or acts as if ‘driven
- Reluctant to engage in tasks that by a motor’
require sustained effort - Talks excessively
- Often loses things needed for a task - Blurts out answers before hearing the
- Easily distracted whole question
- Often forgetful in daily activities - Has difficulty awaiting turn
- Interrupts of intrudes on others
2. Prevalence in ADHD
o 5.9-7.1% (Wilcut, 2012)
o Reports in the media that prevalence rates are going up BUT
o Polanczyk et la., 2014…
154 studies published between 1985 and 2012
Only studies that defined ADHD according to strict criteria, prevalence remained
virtually unchanged
3. How is ADHD diagnosed?
o Typically, via a psychiatric assessment (interviews, observations).
o DSM-V criteria (sensitivity rates 70-90%, Weiler et al., 2000):
Symptoms causing impairment present before age 7
- Can be diagnosed as early as 4 years (American Academy of Pediatrics, 2011), but most
diagnoses mid childhood (Wiloughby, 2013) and only 7-20% of 6-year-olds with ADHD show
persistent features earlier in development (Galera et al., 2011)
Impairment from symptoms occurs in two or more settings
Clear evidence of significant functional impairment (social, academic)
Symptoms not accounted for by another psychiatric / mental disorder
o However – There is no gold standard criteria/ test/ cognitive marker, but there are some direct measures
of inattentiveness & impulsivity that can be used
o Conners Continuous Performance Test (Connors, 1996) for children aged 8+.
, Respond to targets and ignore non-targets
Uses response speed, false alarms, misses and hits
Inattentiveness: is characterized by higher-than-average misses
Impulsivity: characterized by commission errors (false alarms and anticipatory responses)
o But ADHD is most commonly diagnosed via interviews and questionnaires:
Conners 3rd Edition parent / teacher / self report scale
Strengths and Difficulties Questionnaire (includes a hyperactivity scale) is often used as an initial
screener
o Diagnostic challenges:
Subjective criteria (i.e., might be a problem for one family / teacher, but not another)
Many non-specific problems that overlap with other disorders (poor sleep, poor motor control,
literacy/learning difficulties, aggression)
Many ADHD-specific traits feature in other disorders
EEG? Could EEG diagnosis overcome the challenges
posed using behavioural diagnosis?
- Its readily accessible and inexpensive.
- Reminder: it captures neuronal ensembles of the
cerebral cortex
- Different rhythms characterize different cognitive states
- Sleep – slow delta waves
- Concentration – high frequency beta activity
- Meditative state – theta
- Jasper et al (1938) reported a slowing of the EEG rhythms at fronto-central
sensors in “behavioural problem children” described as hyperactive, impulsive and
highly variable.
- But, 75 years on, clinical applications of EEG in psychiatry are controversial, with
methodological limitations and a lack of diagnostic studies (Weder, 2013; Cortese &
Castellanos, 2012; Loo & Makeig, 2012
- Early reports of EEG waves to diagnose ADHD were promising with initial studies showing:
- Theta/beta ratio (TBR): Increased theta (4-7Hz, slow waves) and/or decreased beta (14-30Hz,
fast waves) (Barry et al., 2003; Lubar, 1991).
- There were early reposts of medium to large effect sizes for group differences:
- Ranging from .62-3.08 (Snyder & Hall, 2006; Boutros et al., 2005)
- With diagnostic sensitivity rates of 90% which exceeds the behavioural interview/questionnaire
measures on the DSM V criteria (Quintana et al., 2007; Monastra et al., 2001; Arns et al.,
2013)
Sensitivity is the ability of a test to correctly identify those with the disease (true positive rate)
Specificity is the ability of the test to correctly identify those without the disease (true negative rate).
- Neuropsychiatric EEG-Based But
Assessment (NEBA) offered in private - No agreed cut-offs (i.e., method not
clinics (e.g. Science Park) fully standardised)
- Costs roughly £350 - No checks of reliability / validity
- Calculates ratios of theta and beta brain - No thorough research evaluation
waves (only one study to date carried out by
- Approved by US FDA: “Diagnosing NEBA Health, which hasn’t been
ADHD is a multistep process based on published in a peer reviewed journal,
a complete medical and psychiatric “triple-blinded protocol showed only
exam. Used along with these important 61% agreement between individual
steps, the new system may help clinicians and a multidisciplinary team.
healthcare providers more accurately However, that rate improved to 88%
determine if ADHD is the cause of a once the NEBA system was added.”
behavioural problem.” Christy
Foreman
