how does DSM show it is based in empirical research & clinical observation
(in regards to classification systems for dev differences)
- updates reflect changes in knowledge & understanding
- can be widespread disagreement about how best to characterise conditions
- expect continued change based on new research
limitations of descriptive/diagnostic approach
(classification systems for dev diffs)
- assumes disorders are categorical but are they?
- tends to ignore social & cultural contexts in which conditions emerge & evolve
- diagnostic descriptions imply dev diffs are static
what are neurodevelopmental differences?
(classification systems)
- characterised by atypical development
- differences first appear during childhood
- differences frequently continue into adulthood
challenges and outstanding questions
(classification systems for developmental differences)
- current diagnostic systems are ‘best guess’ but should be updated with changes in knowledge & understanding
- more fundamental questions over whether categorical systems match the clinical reality of developmental differences
key questions
(classification systems for developmental differences)
- etiology
- epidemiology
- co-occurring conditions
- developmental trajectories
etiology
key questions - classification systems
what are the origins or causes of each type of neurodevelopmental difference?
epidemiology
key questions - classification systems
what is the prevalence of each neurodevelopmental difference in the population and what factors influence this?
co-occurring conditions
key questions - classification systems
which neurodevelopmental differences typically co-occur and why?
developmental trajectories
key questions - classification systems
how do differences develop over time?
three levels framework
frith (2001)
- biological
- cognitive
- behavioural
etiology
frith (2001)
- developmental differences are based on behaviour but this is unsatisfactory - observing extreme/atypical behaviour cannot tell us why that behaviour occurs
- theories are needed to explain: the cognitive level may be best for this
epidemiology
- studies of prevalence of conditions, but also characteristics of populations with that difference
- the question of how many people have a neurodevelopmental difference within the population is not straightforward
- true rate & estimated prevalence may not be the same
prevalence of autism
- first recorded = 0.4/1000 (Lotter, 1966)
- more recent = 3-10/1000
reasons for increase
(prevalence of autism)
- increase is real
- change in boundaries of diagnostic category
- current rate is correct but there hasn’t been an increase
increase is real
prevalence of autism increasing
- something in environment is making more people autistic?
- introduction of MMR vaccine? - no research supports temporal association & no plausible causal explanation
change in boundaries of diagnostic category
prevalence in autism increase
- may or may not be appropriate
- hard to tell as no litmus test that captures all cases
the current rate is correct but there hasnt been an increase
prevalence of autism increase
- boundaries between diagnoses have changed
- increasing recognition of co-occurring conditions
- improvements in case-finding methods
- populations sampled
- increased public awareness
co-occurring diagnoses
kaplan et al. (2001)
- sample of 179 children & families recruited from clinics, special schools
- all had dyslexia and/or ADHD
- comprehensive assessment for ADHD, dyslexia, DCD & psychiatric conditions
- co-occurring conditions the norm, not the exception
autism & DLD
developmental language disorder
- autism diagnosed based on diffs in social functioning & communication & repetitive behs/restricted interests
- DLD diagnosed in children when lang doesn’t follow typical dev course
- autism & DLD together should be extremely rare (predicted co-occurrence 0.07%)
- is actually 57%
multiple deficit approaches
pennington (2006)
neurodevelopmental differences arise from multiple environmental & genetic factors that increase likelihood of that diagnosis
matched groups approach
- classic approach for investigating cognitive or behavioural diffs
- neurodevelopmental different group
- chronological age matched comparison group
- mental age matched comparison group
matched groups designs
- researcher needs to make decision about what to match on & what task to use to achieve this
- neurodevelopmental different groups frequently have uneven profiles of performance on standardised tests
developmental trajectories
- trajectories approach - construct a function linking performance on task X with age
- examine whether the function differs for typically developing & neurodevelopmental diff groups
- also aims to construct developmental relations between tasks
hypothetical developmental trajectories
- delayed onset
- slowed rate
- delayed onset & slowed rate
- non-linearity
- premature asymptote
- group averaged data
