On Jan. 12, a few days after registration opened at Yale for Psyc 157, Psychology and the Good Life, roughly 300 people had signed up. Within three days, the figure had more than doubled. After three more days, about 1,200 students, or nearly one-fourth of Yale undergraduates, were enrolled.

The course, taught by Laurie Santos, 42, a psychology professor and the head of one of Yale’s residential colleges, tries to teach students how to lead a happier, more satisfying life in twice-weekly lectures.

“Students want to change, to be happier themselves, and to change the culture here on campus,” Dr. Santos said in an interview. “With one in four students at Yale taking it, if we see good habits, things like students showing more gratitude, procrastinating less, increasing social connections, we’re actually seeding change in the school’s culture.”

Dr. Santos speculated that Yale students are interested in the class because, in high school, they had to deprioritize their happiness to gain admission to the school, adopting harmful life habits that have led to what she called “the mental health crises we’re seeing at places like Yale.” A 2013 report by the Yale College Council found that more than half of undergraduates sought mental health care from the university during their time there.

“In reality, a lot of us are anxious, stressed, unhappy, numb,” said Alannah Maynez, 19, a freshman taking the course. “The fact that a class like this has such large interest speaks to how tired students are of numbing their emotions — both positive and negative — so they can focus on their work, the next step, the next accomplishment.”

Students have long requested that Yale offer a course on positive psychology, according to Woo-Kyoung Ahn, director of undergraduate studies in psychology, who said she was “blown away” by Dr. Santos’s proposal for the class.

Administrators like Dr. Ahn expected significant enrollment for the class, but none anticipated it to be quite so large. Psychology and the Good Life, with 1,182 undergraduates currently enrolled, stands as the most popular course in Yale’s 316-year history. The previous record-holder — Psychology and the Law — was offered in 1992 and had about 1,050 students, according to Marvin Chun, the Yale College dean. Most large lectures at Yale don’t exceed 600.