Feeling happy? Enjoying life? Our quality of life rides upon more than objective social or economic measures–our state of health, employment, or nourishment. Much of our satisfaction (or dissatisfaction) comes from how we feel about our lives, and this depends, in part, upon our genetic make up.
For many years psychology researchers have believed that feelings of well-being run in families. Studies based on surveys of twins and families have estimated around 40 percent of the variance in happiness (or “subjective well-being”) between one person and another is influenced by genetic factors.
Now, behavioral geneticists, economists and social scientists report the first evidence based on molecular data for the role of genetics in determining subjective well-being or SWB. They present their findings in PNAS Early Edition.
Meike Bartels, from VU University Amsterdam, and her team examined a pool of about twelve thousand unrelated, fully genotyped people (combining data from the Swedish Twin Registry and the Rotterdam Study). They used genetic polymorphisms, segments of DNA that differ between one person and another, to find single nucleotide polymorphisms (SNP) associated with subjective well-being.
For their analysis they estimated “common narrow heritability”–the variance within a group that is from many genes adding up to cause a cumulative effect. (Height, for example, is determined by many genetic factors which combine to produce a person’s adult height.) They arrived at this estimate through a relatively new statistical test: genomic-relatedness-matrix restricted maximum likelihood or GREML. Bartels believes this test has the potential to transform the field.
“Normally large gene-finding projects were launched based on the heritability estimates from twins studies,” she says, “but is based on an indirect estimate. The GREML method adds to this the information whether genetic variants of interest are represented on the current SNP chips, so really based on the genetic information itself.”
The team reports 12-18 percent of SWB variance is likely due to additive genetic factors, or narrow heritability. (Another fraction, they believe, is due to broad heritability, the non-additive effects of interactions between genes.)
Although our genes play a role in determining our general level of happiness, the team rejects any claim that interventions to increase SWB are useless.
“Some genetic effects may be mediated by modifiable environmental variables,” the authors write. For example, “the very same genotype may cause a person to grow to 5 feet or 6 feet tall, depending on nutritional intake.”
Also, genetics only influence a portion of SWB. A large portion is influenced by other factors which we may be able to control. And an intervention can change the rules of the game entirely. In 1979 Arthur Goldberger, writing on heritability, offered an analogy: Poor eyesight is largely determined by genetics, but the right set of glasses can restore near 20/20 vision.