intermediate phenotype - quantitative biological trait that is reliable in reflecting the function of a discrete biological system, and is reasonably heritable, and is much more closely related to the root cause of the disease than the broad clinical phenotype.
biological or psychological phenomena of a disorder believed to be in the causal chain between genetic contributions to a disorder and diagnosable symptoms of psychopathology.
measurable biomarkers that are correlated with an illness, in part because of the shared underlying genetic influences.
What conditions need to be met?
Associated with illness in the population
Heritable
Primarily state-independent
Co-segregate with illness in families
Found in unaffected family members at a higher rate than general pop.
Examples of endophenotypes for MDD (major depressive disorder): learning/memory impairments, reduced reward functioning, increased stress sensitivity, REM sleep abnormalities, dysfunctions in serotonergic, catecholaminergic, HPA axis, corticotropin-releasing hormone systems, intracellular signal transduction measures.
Sources of endophenoytpes:
Stress data - cortisol
arousal/attention - pupil dilation
Reaction time / accuracy - behavior
Strength - grip force
Pulse/heart rate
Oxygen
Speech/voice data
Handwriting
Plasma (inflammation markers)
Saliva
Movement - sleep cycles
Temperature
Skin conductance (galvanic skin response)
Transcriptomics
fMRI BOLD signal
Cortical thickness/anatomy
Mobility data (tracked with phone)
Internet search history (tracked with phone)
Social media engagement (reddit, facebook etc)
Electronic health records (hospital admissions etc.)