Week 1
Lecture 1: Etiology of mental traits and conditions
You understand and can explain the concept of heritability
Heritability is not “how genetic a disorder is.”
It means: how much of the differences between people can be explained by differences in
their genes.
So:
● It’s about variation in a population, not individuals.
● High heritability does NOT mean environment is irrelevant.
● If heritability = 80%, it means 80% of differences in that sample are due to genetic
variation, not that genes cause 80% of your disorder.
You can estimate the heritability of depression, ADHD, bipolar disorder, autism,
schizophrenia
● Depression: 40–50%
● ADHD: 75%
● Autism: ~80%
● Bipolar disorder: ~80%
● Schizophrenia: ~80%
,You can describe contribution of genes and environmental factors to the etiology of
complex multifactorial psychiatric disorders
All major psychiatric disorders are complex, multifactorial conditions.
This means:
● Many genes (each with tiny effects)
● Many environmental factors (some protective, some harmful)
● Both interact dynamically
Genes provide risk, environment shapes whether these risks get expressed. This creates a
“complex puzzle” where multiple processes influence each other (stress system, epigenetics,
development, social context).
You can elaborate on the concept of complex genetics and the stress –diathesis model
Complex genetics
● No single “gene for depression” or “gene for ADHD.”
● Instead, people inherit a bundle of small-risk variations.
● These add up and bias someone toward vulnerability.
● You inherit risk, not the disorder.
This explains “missing heritability”:
→ Risk comes from many genes + lots of environmental shaping.
Stress-diathesis model
● Diathesis = genetic predisposition
● Stress = environmental triggers
● Disorder emerges when stress exceeds someone’s capacity to cope, given their
vulnerability.
,This model applies to major depression, schizophrenia, bipolar, anxiety disorders, obesity,
diabetes, and more.
You can explain biological endophenotypes and system endophenotypes
and can give examples
Endophenotypes help bridge “gene → disorder” by adding an intermediate step.
They’re measurable, inheritable features linked to mental illness.
Biological endophenotypes
These are physical/biological markers:
● Startle reflex response
● Brain activation patterns on fMRI
● Specific neural circuit activation
● EEG responses
These sit closer to genes on the pathway.
System / Symptom endophenotypes
These are single symptoms:
● Insomnia
● Executive dysfunction
● Hallucinations
● Poor fear conditioning
● Anhedonia
Easier to link a gene to a single symptom than to a whole diagnosis like “bipolar disorder.”
, You understand the ‘Social-ecological framework’, that no single factor can explain traits
and disorders. That there is a dynamic interplay of multiple risk and protective factors
This model says no single factor explains mental traits or disorders.Instead, risk &
protective factors exist at many levels:
Individual level:
● Genes
● Temperament
● Cognitive traits
● Stress sensitivity
Relationship level:
● Parenting
● Attachment
● Social support
● Family conflict or trauma
Community level:
● Poverty
● Neighborhood violence
● School environment
Lecture 1: Etiology of mental traits and conditions
You understand and can explain the concept of heritability
Heritability is not “how genetic a disorder is.”
It means: how much of the differences between people can be explained by differences in
their genes.
So:
● It’s about variation in a population, not individuals.
● High heritability does NOT mean environment is irrelevant.
● If heritability = 80%, it means 80% of differences in that sample are due to genetic
variation, not that genes cause 80% of your disorder.
You can estimate the heritability of depression, ADHD, bipolar disorder, autism,
schizophrenia
● Depression: 40–50%
● ADHD: 75%
● Autism: ~80%
● Bipolar disorder: ~80%
● Schizophrenia: ~80%
,You can describe contribution of genes and environmental factors to the etiology of
complex multifactorial psychiatric disorders
All major psychiatric disorders are complex, multifactorial conditions.
This means:
● Many genes (each with tiny effects)
● Many environmental factors (some protective, some harmful)
● Both interact dynamically
Genes provide risk, environment shapes whether these risks get expressed. This creates a
“complex puzzle” where multiple processes influence each other (stress system, epigenetics,
development, social context).
You can elaborate on the concept of complex genetics and the stress –diathesis model
Complex genetics
● No single “gene for depression” or “gene for ADHD.”
● Instead, people inherit a bundle of small-risk variations.
● These add up and bias someone toward vulnerability.
● You inherit risk, not the disorder.
This explains “missing heritability”:
→ Risk comes from many genes + lots of environmental shaping.
Stress-diathesis model
● Diathesis = genetic predisposition
● Stress = environmental triggers
● Disorder emerges when stress exceeds someone’s capacity to cope, given their
vulnerability.
,This model applies to major depression, schizophrenia, bipolar, anxiety disorders, obesity,
diabetes, and more.
You can explain biological endophenotypes and system endophenotypes
and can give examples
Endophenotypes help bridge “gene → disorder” by adding an intermediate step.
They’re measurable, inheritable features linked to mental illness.
Biological endophenotypes
These are physical/biological markers:
● Startle reflex response
● Brain activation patterns on fMRI
● Specific neural circuit activation
● EEG responses
These sit closer to genes on the pathway.
System / Symptom endophenotypes
These are single symptoms:
● Insomnia
● Executive dysfunction
● Hallucinations
● Poor fear conditioning
● Anhedonia
Easier to link a gene to a single symptom than to a whole diagnosis like “bipolar disorder.”
, You understand the ‘Social-ecological framework’, that no single factor can explain traits
and disorders. That there is a dynamic interplay of multiple risk and protective factors
This model says no single factor explains mental traits or disorders.Instead, risk &
protective factors exist at many levels:
Individual level:
● Genes
● Temperament
● Cognitive traits
● Stress sensitivity
Relationship level:
● Parenting
● Attachment
● Social support
● Family conflict or trauma
Community level:
● Poverty
● Neighborhood violence
● School environment
