Heritability
Heritability is a concept that is frequently misunderstood. It is often thought of as a measure of the extent to which genes cause a condition in an individual, this is incorrect. The main point to note is that heritability tells us nothing about individuals. Heritability is the proportion of phenotypic variance attributable to genetic variance. This means that if a condition has a heritability of 0.80 then 80% of the variance of that condition seen in a population is attributable to genetic variation. The remaining 20% is attributable to environmental factors.
It is calculated by complicated statistical techniques. It can be estimated by looking at monozygotic twins reared apart to see to what extent they are similar.
Heritability is a proportion, its numerical value will range from 0.0 (genes do not contribute at all to phenotypic individual differences) to 1.0 (genes are the only reason for observed differences). For human behaviour, almost all estimates of heritability are in the moderate range of .30 to .60.
The quantity (1.0 - heritability) gives the environmentability of the trait. Environmentability has an analogous interpretation to heritability. It is the proportion of phenotypic variance attributable to environmental variance or the extent to which individual differences in the environment contribute to individual differences in behaviour.
It is calculated by complicated statistical techniques. It can be estimated by looking at monozygotic twins reared apart to see to what extent they are similar.
Heritability is a proportion, its numerical value will range from 0.0 (genes do not contribute at all to phenotypic individual differences) to 1.0 (genes are the only reason for observed differences). For human behaviour, almost all estimates of heritability are in the moderate range of .30 to .60.
The quantity (1.0 - heritability) gives the environmentability of the trait. Environmentability has an analogous interpretation to heritability. It is the proportion of phenotypic variance attributable to environmental variance or the extent to which individual differences in the environment contribute to individual differences in behaviour.
| Condition | Heritability estimate |
|---|---|
| Bipolar | 80-95% |
| Autism | 90% |
| Schizophrenia | 80-85% |
| ADHD | 80% |
| OCD | 25-50% |
| Panic disorder | 45% |
| Anorexia | 55% |
| Alcohol dependence | 50-60% |
| Major depression | 35-50% |
