People who have a version of the 5-HTT gene, a gene efficient at moving serotonin (known to improve mood), are more likely to be satisfied with their lives. So says research out of the London School of Economics and Political Science. But before you think you're predestined for happiness or not, you can affect your mood. Studies have shown that performing acts of kindness or even listing what you're grateful for can help you to feel happy.
But if you put too much emphasis on being happy you can find yourself depressed, according to a study in the journal Emotion.
Happiness, like everything else, is a balance.