Comorbidity in developmental dyslexia Flashcards
What is comorbidity?
The simultaneous presence of 2 chronic diseases or conditions in a patient. They are associated in time but not related.
What is co-occurrence?
Occurring together or simultaneously. Associated by not necessarily related.
Give an example of co-morbidity and one of co-occurrence.
Co-morbidity: heart disease and diabetes (have similar cause so occur together but not actually related).
Co-occurrence: diabetes and asthma (they can occur together but are not related at all, many people have asthma and not diabetes)
Moll et al. (2014)
Dyslexia co-occurs with other developmental disorders at rates that are higher then chance
Moll et al. (2017)
Single learning disorders are as common as comorbid LDs in spelling, reading and arithmetic. Relative commonality of pairs of disorders shows differences in aetiology of comorbidity.
Kaplan et al (1998)
Dyslexia co-occurs with dyspraxia (DCD): 50% with dyslexia meet DCD criteria
Gilger et al. (1992)
Dyslexia co-occurs with ADHD: 25-40% of children with ADHD have dyslexia.
Kaplan et al. (2006)
ADHD- DCD- Dyslexia: 36% of children with DCD met criteria for ADHD and Dyslexia.
Catts et al. (2005)
Dyslexia co-occurs with specific language impairments: 31-35% of children with SLI develop later literacy difficulties
Bishop & Pennington (2009)
Reading difficulty more likely In multi deficit models genes will be shared and independent factors contributing to cognitive skills and have probabilistic influences (not on/off) and so act as a quantitative trait loci rather than a major gene.
More Genome Wide Association Studies to reduce linkages found by chance.in children with both Speech sound disorder and Language impairment.
Landerl & Moll (2010)
11-56% of children with Developmental dyscalculia (DD) have dyslexia.
(17-70% of children with dyslexia have DD)
Kadesjo & Gillberg (2001)
Half the population of 7 y/o in a swedish town clinically examined and parents and teacher interviewed. Diagnosed with ADHD, DCD, ODD, Aspergers, Tic disorders and reading/writing disorders.
Found that pure disorders are the exception not the rule.
Willcutt et al. (2007)
Twins with reading difficulty and ADHD. Both individually highly heritable. Genetic influences primarily responsible for association between RD and inattention. Association between RD and Hyperactivity/impulsivity did not have significant genetic influence.
What is the alternate form explanation for co-morbidity in dyslexia?
The co-morbid version of dyslexia and another disorder is another type of dyslexia.
What is the random multiformity explanation for co-morbidity in dyslexia?
Where having one disorder increases risk to have another disorder.
What is the extreme multiformity explanation for co-morbidity in dyslexia?
Extreme cases of a disorder lead to increased risk of the second co-morbid disorder.
What is the three independent disorders explanation for co-morbidity in dyslexia?
Co-morbid version of e.g. dyslexia with ADHD is another form of dyslexia
What is the correlated liabilities explanation for co-morbidity in dyslexia?
The correlation between risk factors for a disorder means that disorders who’s risk factors correlate will occur together more often.
What is the direct causal model explanation for co-morbidity in dyslexia?
The 2 co-morbid disorders have a cause in common.
What do estimates for co-morbidity being greater than chance indicate and what potential limitations may also cause this?
A shared causal risk factor such as genetic variants, causal mechanisms and environmental factors. May be due to biased sampling or rater bias.
Bishop & Pennington (2009) biased sampling
Biased sampling as many participants are clinic referred and the chance of being referred increases with co-morbidity. Also there is parent and teacher bias from the interviews.
Semrud-Clikeman et al. (1992)
Results occur at a rate better then chance in clinic referred samples: 38% ADHD in LD
Wilcutt & Pennington (2000)
Results occur at a rate better than chance in non-referred community samples: boys with RD 31% ADD, without RD 9%, and for girls with RD 22% and without 5%.
What is rater bias?
You are more likely to rate ADHD symptoms highly if you already have reading difficulties.