In 2018, when Professor Laurie Santos introduced her course "Psychology and the Good Life," a class on the science of happiness, it became the most popular in the history of Yale, attracting more than 1,200 undergraduate enrollees that first semester. An online course based on those teachings became a global phenomenon. By latest count, 3.38 million people have enrolled to take the free Coursera.org course, called "The Science of Well Being."

But the popularity of the course posed an interesting question. Does taking the course and participating in homework assignments—which include nurturing social connections, compiling a gratitude list, and meditation—really help improve a sense of well-being?

The answer is yes, according to two new studies that measured the psychological impact on individuals who took Santos's or a similar course. The findings suggest that free online courses that teach principles of positive psychology can enrich the lives of millions of people.

In the latest study, published April 14 in the journal PLOS ONE, researchers at Johns Hopkins University and Yale found that people who took the online "Science of Well Being" course reported a greater sense of well-being than those enrolled in another Yale Coursera course, "Introduction to Psychology." Although learners in both classes said they experienced significant improvement in their well-being after taking the courses, those who took the "Science of Well-Being" course reported greater mental health benefits than those learning about the basics of psychology.

Unlike the psychology course, "The Science of Well Being" requires participants to do exercises known to improve psychological health, such as improving sleep patterns, developing exercise routines, and practicing meditation, the authors say. Before and after taking the course, participants answered questions designed to measure factors related to psychological health such as positive emotions, engagement, and strength of relationships.

"Knowledge is great but it isn't enough. You also have to do the work," said lead author David Yaden, research fellow in the Department of Psychiatry and Behavioral Sciences at Johns Hopkins.

A similar study in Health Psychology Open, conducted by researchers at Yale and the University of Bristol, surveyed people who took either a live or an online credit-bearing course based on Santos's original class and found similar psychological benefits for enrollees.

Yaden stressed, however, that the classes are not a substitute for professional treatment for those who suffer from diagnosed mental illness. "These courses are not a panacea or replacement for psychotherapy or medication," he said.

However, both Yaden and Santos, who co-authored the study, say the findings show that massive open online courses can provide at least modest value to millions of people at no cost.

"We wanted to know if we could scale these benefits and we can," Santos said. "Even bringing a small mental health benefit to millions of people can have a huge value."