Source"When it comes to that quintessential American passion, the pursuit of happiness, the news from science is mixed.
The good news is that the sting of life's slings and arrows is surprisingly short. The bad news is for vacationers: the mellow glow from a week or two away will fade just as surely.
Happiness, many psychologists are concluding, seems to be largely determined by the genes, not by outside reality. However tragic or comic life's ups and downs, people appear to return inexorably to whatever happiness level is pre-set in their constitution.
The idea is similar to the set-point concept in weight control, a theory that says the brain seems to be wired to turn the body's metabolism up or down to maintain a pre-set weight.
There is also, these scientists contend, a set point for happiness, a genetically determined mood level that the vagaries of life may nudge upward or downward, but only for a while. With time, the grouchy tend to become as cranky as before, and the light-hearted cheery again.
Interviews with a range of psychologists show that the idea of a biological set point for a sense of well-being has wide support in the field, though there are quibbles on details.
"It's a brilliant idea -- it's well worth pursuing," said Dr. Jerome Kagan, a developmental psychologist at Harvard University who has studied temperament in children. "It's clear that T.S. Eliot was by nature dour, and Jay Leno is congenitally upbeat. But we're far from filling in the biological blanks."
The set-point idea seems to make sense of long-standing data on happiness that have puzzled researchers. Some of the studies simply take people's word for how happy they are, while others use less direct measures -- like observing how exuberant they are.
Studies of happiness in several countries have found that money makes little difference to perceptions of happiness, except among the very poor. Nor do education, marriage and a family, or any of the many other variables that researchers have sought to correlate with contentment. Each factor may make a person a little happier, but it has a minor impact, compared with the individual's characteristic sense of well-being.
"We find that for events like being promoted or losing a lover, most of the effect on people's mood is gone by three months, and there's not a trace by six months," said Dr. Edward Diener, a psychologist at the University of Illinois at Urbana. Diener, with his wife, Dr. Carol Diener, also a psychologist there, proposed the notion of a happiness set point in the May issue of the journal Psychological Science.
Forget those if-only-I-could-win-the-lottery-I'd-find-happiness-forever fantasies; Dr. Edward Diener cites data showing that lottery winners are no happier a year after their good fortune than they were before. And several studies show that even people with spinal-cord injuries tend to rebound in spirits.
The set-point concept has been seized by some genetics researchers, who say new data on twins give the strongest support to date for that idea.
"About half of your sense of well-being is determined by your set point, which is from the genetic lottery, and the other half from the sorrows and pleasures of the last hours, days or weeks," said Dr. David T. Lykken, a behavioral geneticist at the University of Minnesota who published results from a study of 1,500 pairs of twins in the May issue of Psychological Science. His estimates are based on comparing how members of pairs of fraternal and identical twins rate their sense of well-being.
A common way to estimate how much of a trait is based on genetics is to look at the similarities that show up in identical twins, who share their genes 100 percent, compared with fraternal twins, who are no more similar genetically than any other siblings.
"There is little difference in well-being among identical twins raised together, compared with those raised apart," said Dr. Auke Tellegen of the University of Minnesota, a co-author of the study with Lykken.
Life circumstances, like salary, education or marital status, predicted only 2 percent of the variation within each pair of twins, Lykken said.
"Those in prestigious positions or professions were not happier than those who went to work in overalls, nor were those who finished their Ph.D.'s happier than those who never completed eighth grade. You can predict happiness levels vastly better just by knowing the other identical twin's score."
Still, doubts remain about the set-point idea. Dr. Howard Weiss, a psychologist at Purdue University, takes issue with Lykken's estimate that about 50 percent of a person's sense of well-being is due to an inherited set point.
"A heritability estimate based on a single study has to be viewed with caution," Weiss said. "Though no one is disputing a part of your satisfaction in life is due to genetic factors, we don't really know yet if it's 25 percent, 50 percent or 75 percent."
The idea that a person's typical mood persists over time has been borne out by data from several large studies that followed people over many years. One is the National Health and Nutrition Examination, which monitored reports of well-being from close to 6,000 men and women over 10 years.
"We find that the people who are relatively happiest now will be the happiest 10 years from now, despite the day-to-day fluctuations," said Dr. Robert R. McCrae, a research psychologist at the National Institute on Aging, who analyzed the data with a colleague, Dr. Paul T. Costa.
Supporters of the set-point idea agree that people can have deep mood changes for the worse after a serious trauma or loss. But researchers say that if such shifts persist for years, they mark clinical problems like depression that are overriding the set point for well-being, or they are being caused by serious disturbances that continue to prime the bad mood.
"For most of the widowed, or those who lose a job or get divorced," Dr. Edward Diener said, "the impact on daily mood disappears after a year or so. But when there is a more lasting effect on mood, it's because in some sense the bad event continues to happen -- there are reminders every day."
Even major setbacks in life, like being bereaved or divorced, "didn't change the stability of people's well-being in the long term," McCrae said.
"Years afterward, you see people return to whatever their basic level of well-being had been 10 years before," he added. "Those who were still depressed tended to be those who had been relatively depressed 10 years earlier."
Along with a set point for well-being, people also have typical ranges of ups and downs, researchers say. "There's a range of oscillation around a given person's stable set point," Tellegen said. "This latitude means that you can be an emotional Pavarotti, with extreme ups and downs, and it will still average out, tending to return to the same basic level."
Scientists who study changes within the brain say they may have even located an important area where happiness is registered and where the set-point mechanism may operate.
In studies with colleagues over the last decade, Dr. Richard Davidson, a psychologist at the University of Wisconsin, has found a strong relationship between the ratio of neural activity levels on the left and right sides of the prefrontal lobes and people's typical moods.
"Those with relatively more activity in the left prefrontal area report more positive emotions," Davidson said. "They say they get more pleasure from life's ordinary activities, rate themselves as more enthusiastic, energetic and alert" in general than do those who have more activity on the right side. By contrast, those with relatively more right prefrontal activity report being more agitated, nervous, distressed and worried.
The people with the most right prefrontal activity, compared with the activity on the left, are those with clinical depression who say they have lost all sense of pleasure in life, Davidson found after studying brain changes in 25 patients with the imaging technique known as positron emission tomography scans.
Davidson, though not guided by the set-point theory, has found that in infants as young as 10 months, those with more active left prefrontal lobes are less likely to cry when separated briefly from their mother. The brain-activity patterns tend to remain stable when tracked over several years. For instance, Dr. Davidson found that children's brain-wave patterns -- as shown in electroencephalographs, or EEG's -- at age 3 predict their exuberance at age 7.
When 7-year-olds in Davidson's study were asked to jump to pop bubbles blown over their heads, those with relatively more right-side prefrontal activity "were very restrained, just going up a bit on their tippy toes," Davidson said. But those with more activity on the left "were hopping all over, laughing and going bonkers."
Davidson says his findings seem to be related to receptors for the neurotransmitter dopamine. Animal studies suggest that a dopamine-mediated pathway from the left prefrontal areas to the emotional centers in the limbic area of the brain regulates positive emotions and that the left medial area of the prefrontal cortex is the site for inhibiting the signals for emotional distress. A 1995 study by Dr. Richard Depue, a psychologist at Cornell University, found that the higher people's levels of dopamine, the more positive their feelings.
A possible genetic basis for such differences in people's typical dopamine levels may have been found in research reported in January in the journal Nature by an Israeli group. Those researchers found that people differed in an allele for a portion of the D4 dopamine receptor that regulates how much dopamine binds there and that the differences were related to the moods people reported. The discovery, Davidson said, "is very exciting because it's the first time there's been a specific connection between a molecular genetic finding and people's levels of happiness."
Some psychologists dispute the choice of happiness itself as an index of the good life.
"Satisfaction is a byproduct of a life that involves more than the mere pursuit of happiness," said Dr. Carol Ryff, a developmental psychologist at the University of Wisconsin. "I would argue that it's worse to wake up in the morning without having a larger purpose in life than to wake up unhappy. Just feeling good is a poor measure of the quality of a person's life."
Lykken sees in his data a recipe for living that calls for nudging one's level of happiness into the higher registers of one's range. Lykken's advice:
"Be an experiential epicure. A steady diet of simple pleasures will keep you above your set point. Find the small things that you know give you a little high -- a good meal, working in the garden, time with friends -- and sprinkle your life with them. In the long run, that will leave you happier than some grand achievement that gives you a big lift for a while." "
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