2.1.6—Genetic inheritance
- Syllabus
- First assessment 2027
- Objective
- 2.1.6
- Level
- SL
Genes alter probability, not a fixed psychological fate
Genetic inheritance can contribute to vulnerability through many variants and biological pathways. A heritable tendency describes variation in a population, not a guaranteed outcome for one person.
Twin or family evidence can estimate similarity, but shared environments and gene–environment interaction complicate interpretation. A risk variant may matter only under particular developmental or social conditions.
If identical twins show different depression outcomes, genetic influence is compatible with the result: genes may alter sensitivity while stress, support and learning change exposure and expression.
Heritability is not the percentage of an individual's disorder caused by genes. Avoid deterministic or stigmatizing conclusions.