If you want to live longer—and help your veterinary patients do the same—smile. That’s the suggestion of a new study that reviews more than 160 studies on human and animal subjects and their happiness. Researchers found evidence that happy people tend to live longer and experience better health than their unhappy peers. The study, published in the journal Applied Psychology: Health and Well-Being, is the most comprehensive review so far of the evidence linking happiness to health outcomes.
Researchers analyzed long-term studies of human subjects, experimental trials, and studies that evaluate the health status of people stressed by natural events. The general conclusion is that your subjective well-being contributes to both longevity and better health among healthy populations. In most of the long-term studies, the researchers found that anxiety, depression, lack of enjoyment of daily activities, and pessimism are all associated with higher rates of disease and a shorter lifespan.
In addition, animal studies also demonstrate a strong link between stress and poor health. Experiments in which animals receive the same care but differ in their stress levels—as a result of an abundance of nest mates in their cages, for example—have found that stressed animals are more susceptible to heart disease, have weaker immune systems, and tend to die younger than those living in less crowded conditions.
Researchers conducting laboratory experiments on humans have found that positive moods reduce stress-related hormones, increase immune function, and promote the speedy recovery of the heart after exertion. In other studies, marital conflicts and high hostility in married couples were associated with slow wound healing and a poorer immune response.
Happiness alone might not prevent or cure disease. However, evidence that positive emotions and enjoyment of life contribute to better health and a longer lifespan is stronger than the data linking obesity to reduced longevity, researchers say. So go on, get happy.