You are diagnosed with a crippling illness. You lose your job. Someone close to you suddenly dies. Some people recover rapidly from life’s calamities and disappointments, whereas others are devastated by minor setbacks, becoming depressed and even suicidal.
The roots of such emotional differences have fascinated psychologists and nonspecialists alike. Environmental factors, such as a person’s upbringing, exert a tremendous influence on his or her resilience in the face of misfortune or failure. But as biologists (and parents) have long suspected, genes lay much of the groundwork for individual personality traits. Studies that compare the traits of identical twins, who have all the same genes, with those of fraternal twins, who share just half their DNA, suggest that genes account for 40 to 60 percent of the individual variation in anxiety levels and susceptibility to depression.