The happier you are, the better, right? Not necessarily. Studies show that there is a darker side to feeling good and that the pursuit of happiness can sometimes make you . . . well, less happy. Too much cheerfulness can make you gullible, selfish, less successful — and that’s only the tip of the iceberg.

Happiness does have benefits (beyond feeling good, of course). It can protect us from stroke and from the common cold, makes us more resistant to pain and even prolongs our lives. Yet, June Gruber, a professor of psychology at Yale University who has studied happiness, warns that it’s important to experience positive moods in moderation.

She compares happiness to food: Although necessary and beneficial, too much food can cause problems; likewise, happiness can lead to bad outcomes. “Research indicates that very high levels of positive feelings predict risk-taking behaviors, excess alcohol and drug consumption, binge eating, and may lead us to neglect threats,” she says.

How else can excessive joy, or having lots of positive emotions and a relative absence of negative ones, hurt you?

First, it may hamper your career prospects. Psychologist Edward Diener, renowned for his happiness research, and his colleagues analyzed a variety of studies, including data from more than 16,000 people around the world, and discovered that those who early in their lives reported the highest life satisfaction (for example, judging it at 5 on a 5-point scale) years later reported lower income than those who felt slightly less merry when young. What’s more, they dropped out of school earlier.

Included in the studies was one involving a group of American college freshmen who in 1976 claimed to be very cheerful. Surveyed again when they were in their late 30s, they earned, on average, almost $3,500 a year less than their slightly less cheerful peers. Why? Diener suggests that people who don’t experience much sadness or anxiety are rarely dissatisfied with their jobs and therefore feel less pressure to get more education or change careers.

Psychologists point out that emotions are adaptive: They make us change behavior to help us survive. Anger prepares us to fight; fear helps us flee. But what about sadness? Studies show that when we are sad, we think in a more systematic manner. Sad people are attentive to details and externally oriented, while happy people tend to make snap judgments that may reflect racial or sex stereotyping.

Fooling the jury

In a 1994 study in the Journal of Personality and Social Psychology, Northwestern University psychologist Galen Bodenhausen and his colleagues asked 94 undergraduates to participate in a simulated “students’ court.” They were told they would be making a judgment after reading about a case that occurred on a different campus. Before the “court” opened, half of the participants were induced into a positive mood (they had been instructed to think and write about an event that had made them feel particularly good), while the other half was asked to recall the mundane events of the previous day (to leave them in a neutral mood). The results were clear: Those in a happy mood were more likely to find a fellow student named “Juan Garcia” guilty of beating up a roommate than one identified as “John Garner.” The control group was pretty much equally divided between “Juan” and “John.”

That happy people are more prone to stereotypic thinking was supported in research by Joe Forgas, a professor of psychology at the University of New South Wales in Australia. In an experiment published in the December 2011 issue of the European Journal of Social Psychology, Forgas asked students to read a philosophical essay by a “Robin Taylor,” to which a photograph of the presumed author was attached. Some of the students received a picture of a middle-aged, bearded man; others of a young woman in a T-shirt. Even though the essays were identical, those students who had been induced to feel happy judged the man’s work more competent than the woman’s. Their non-induced colleagues declared both essays to be of equal quality.

Anyone who has committed a crime should hope that the jury that tries him is happy. According to Forgas, his experiments show that cheerful people are easier to deceive, couldn’t detect lies as easily as those in negative moods and couldn’t tell a thief from an honest person.

Forgas had 117 students watch specially chosen video clips to induce them into either positive or negative moods. Later they were asked to watch another film: an interrogation of people accused of the theft of a movie ticket. Some of the suspects really did steal and were lying about their action; others were honest. Yet those students who were made to feel happy did not detect guilt above chance level (50 percent). Their sad colleagues fared batter: They could spot a thief more often than chance would predict.

And there are more flip sides of happiness: Feeling good makes people more selfish (if asked to divide raffle tickets between themselves and others, they’ll keep more in their pockets than sad people) and worse at defending their opinions (they produce weaker, less detailed arguments). The happiest of us are also less creative than those who describe themselves as just “happy enough.”

Listen to the music

Even just striving to feel cheerful might make us less happy. Jonathan Schooler, a professor of psychology at the University of California at Santa Barbara, and his colleagues asked a group of 120 people to listen to Stravinsky’s “Rites of Spring,” a complex composition that is not that easy on the ear. He discovered that those who listened to the music with a specific intent to make themselves happy or constantly monitored how much they were enjoying themselves ended up enjoying themselves less than those who just focused on the experience.

In another experiment, Schooler found that 83 percent of 475 people interviewed were disappointed with their New Year’s Eve celebrations of 2000. The most dissatisfied? Those who anticipated having a bash and put the most energy into preparations.

“It’s a delicate balance between savoring experiences, being able to appreciate, say, a glass of good wine, and excessively being preoccupied with ‘Am I having fun yet?’ ” says Schooler, who compares striving for happiness with looking at a faint star. If you try to gaze directly at it, it disappears; but if you keep it to the side and don’t make it the focus of your attention, you might actually enjoy it.

Keeping score

According to psychologist Iris Mauss, the more someone pursues happiness, the more he or she will probably end up feeling disappointed. In a study of 43 women published in August 2011 in the journal Emotion, Mauss, then at the University of Denver, showed that those who read a newspaper story designed to induce feelings of happiness felt lonelier after watching Clint Eastwood’s and Meryl Streep’s doomed love in “The Bridges of Madison County” than did a control group whose members were given an emotionally neutral newspaper story to read before watching the movie.

Mauss confirmed her laboratory findings by using diary studies: 206 participants, both men and women, completed happiness surveys and then were asked to fill out diaries on 14 consecutive days in which they wrote about stressful events that occurred and how lonely they felt. Mauss found that those to whom being happy was extremely important felt lonelier after experiencing a stressful event than those who didn’t make such a big deal of wanting to be cheerful.

But don’t burn your “how to be happy” books just yet. “I’d hate to see depressed people, who could gain benefits from self-help books, throwing them out,” says Schooler. “Just don’t keep a score on how happy you are. What’s bad is when people make happiness their explicit goal all the time.”

So how happy is happy enough? Gruber points out that it’s important to accept whatever one’s level of happiness is — as long as you are not clinically depressed, of course — and the negative feelings you may have. Following work of other psychologists, she and her colleagues are now exploring the notion that a good balance to achieve would be experiencing three positive emotions (such as joy, compassion, gratitude or hope) for every one negative (disgust, embarrassment, fear, guilt, sadness).

Zaraska is a Canadian freelance journalist and novelist. She lives in France.