ADHD Flashcards
What is the triad of ADHD?
Inattention
Hyperactivity Impulsivity.
How is ‘inattention’ defined?
Fails to sustain attention, follow through on instructions/work, and listen.
Careless errors
Avoids tasks requiring mental effort
Loses things
Easily distracted.
Forgetting, poor planning.
How is ‘hyperactivity’ defined?
Fidgets or squirms
Leaves seat
Excess running about
Unduly noisy
Excess motor activity.
Impulsivity?
Blurts answers
Fails to wait in lines
Interrupts others
Excessive talking
What is the comorbidity?
- Conduct disorder
- Anxiety & Depressive disorder
- Learning difficulties
- Tourette’s disorder
- Soft neuro signs
- Alcohol and substance misuse
- Offending
What is the ADHD spiral?
ADHD symptoms causes learning difficulties, causing failure at school, leading to low self esteem and isolation.
What are the genetics of family studies?
20% of hyper children had parent reporting childhood hyperactivity.
8x increased risk of child ADHD if parent meets ADHD criteria.
BUT- it could still be environmental.
How would you tease out environment vs genes?
MZ and DZ twin studies.
MZ twins: If one twin has ADHD, 80% concordance.
DZ twins have 30% concordance.
Heritability is 0.76.
What are some candidate genes?
Precursor a.a’s
Receptor genes
Metabolic enzymes
Non-DA sys genes
What have been the genetic findings?
High heritability related to multiple common gene variants of small effect size
Rare mutations bestow higher risk
ADHD genomic variants are non-specific
CNVs overlap are also non specific.
ENVIRONMENT IS IMPORTANT- SMOKING ACTIVATED HIGH RISK ALLELES.
What is the fronto-striatal / executive function hypothesis?
Executive function is top down control of behaviour.
Impulse control, orient to salient stimuli, flexible strategy, planning, suppress inappropriate actions in favour of appropriate ones.
Tested with stroop test.
What is shown in imaging of the prefrontal cortex?
MRI:
Decreased size
Cortical thickness- delay in development by 2-3 years.
Functional imaging:
Less activity on fMRI during EF tasks, less blood low in SPECT.
What is the down-top alternative hypothesis?
Prefrontal cortex receives signalling from other structures.
Posterior parietal cortex signals to prefrontal C when completing stimuli require prioritisation towards one stimulus attribute or location.
Decreased blood flow in PPC in ADHD.
What are the function of the BG and cerebellum?
Learn to predict events and detect irregularities.
Learn what to expect and when.
Signal to prefrontal C when an unexpected or competing events occurs at an unexpected time.
Is it down top or top down dysfunction?
ADHD is a diverse range of EF and non EF deficits.
Pathological & aetiological heterogeneity likely.
