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
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
