Introduction to Developmental Psychology
Understanding Autism Spectrum Disorders
History of Autism Diagnosis
Kanner (1944) – Early Infantile Autism
o “The common denominator in all these patients is their disability to relate
themselves in the ordinary way to people and situations from the beginning
of life” – p.212
o “The case histories indicate invariably the presence from the start of extreme
autistic aloneness…” – p.212
Diagnosing Autism Spectrum Disorders
Persistent deficits in social communication and social interaction across multiple
contexts:
o Deficits in social-emotional reciprocity (e.g. shared affect, conversations)
o Deficits in non-verbal and verbal communication (e.g. eye contact, facial
expressions)
o Deficits in developing relationships (e.g. sharing imaginative play, making
friends)
Restricted, repetitive behaviours, activities or interests:
o Stereotyped, repetitive motor movements or speech
o Insistence on sameness, inflexible routines, ritual patterns of behaviour
o Restricted interests that are abnormal in intensity
o Hyper- or hypo-reactivity to sensory aspects of environment
Core Features of Autism Spectrum Disorders
Communication difficulties
o Echolalia – repeat what was said, either mirror or mimic what was said
around them
o Neologisms – using words that don’t mean anything
o Conversation problems – failure to initiate and seek out conversations
o Language delays
o Poor eye contact
Social interaction difficulties
o Lack of interest in others
o Difficulties with reciprocity
o Difficulties with understanding others’ thoughts/emotions
Restricted, repetitive behaviours and interests
o Stereotyped repetitive movements
o Obsessional interests
o Insistence on sameness
o Unusual memory
, Causal Modelling of Developmental Disorders
Autism is Highly Heritable
Folstein & Rutter (1977)
o 36% of monozygotic twins vs. 0% of dizygotic twins concordant for autism
diagnosis
o First evidence of genetic factors in aetiology of autism
Ronald & Hoekstra (2011)
o Meta-analysis of 7 twin studies
o Median estimate of MZ concordance 76% vs. 0% for DZ twins
Genes and Autism
Genes are made up of about 3 billion base pairs (A, T, G, C)
Approximately 1% of our genes vary alleles
Alleles are polymorphic
Single nucleotide polymorphisms (SNP)
o Gene varies in one part of the code
Psychiatric disorders and complex traits are assumed to be polygenic in origin i.e.,
multiple causes
o For example, genetic causes, biological causes, non-genetic/environmental
causes
Complex Inheritance: Two Perspectives
Complex traits (disorders) are caused by common variants
o Common disease, common variant model
o Caused by many common alleles each having a small effect
Complex traits (disorders) are caused by rare variants
o Multiple rare variants model
o Caused by many mutations (de novo mutations)/rare variants each with a
powerful effect
Genome Wide Association Studies (GWAS)
Look at about 1 million SNPs and tally up what kind of version of each of these you
have
They then compare groups of people with autism vs groups of people who don’t
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