According to a 2018 Harvard study of students in economics Ph.D. programs, 18% of the students were reported to likely have mental health disorders (more than three times the population average), and 11% of the students experienced suicidal thoughts within a two-week period.
There are several factors that can negatively affect a Ph.D. student’s mental health. Ph.D. students typically work well over 40 hours per week for low pay, usually around $30,000 per year as a fellow. Unlike other graduate programs, including medical and law programs, Ph.D. programs don't have a set schedule and number of credits or coursework needed to complete; instead, they’re based on research and publication. While the success or failure of those things can sometimes be out of the student’s control, there is also an element of faculty subjectivity. Negative circumstances, such as research funds running out or hindering publication, can cause a student’s efforts to be in vain. Additionally, universities invest a great deal of time and money into Ph.D. programs and candidates, and there is enormous pressure on the student’s research to potentially be used to procure possibly millions of dollars in research funding for the university. That is a lot of weight for Ph.D. students and faculty to shoulder.
Then there's the dynamic between the student and their supervising professors. While there are many supportive professors, there can also be a power dynamic that can put students in precarious situations. Allegations of sexual harassment, character assassination and manipulation aren’t unheard of, and were recently scandalized at the University of California, Harvard and Columbia University.
Ph.D. students also face a serious lack of job opportunities postgraduation, which can further affect their mental health, even once they have their degree.