A few years back UC Berkeley did a study of the mental health of graduate students. The results were quite astounding.
The study found that 67% of graduate students said they had felt hopeless at least once in the last year; 54% felt so depressed they had a hard time functioning; and nearly 10% said they had considered suicide (note that in the graph below shows considering suicide “frequently” or “all the time”, thus the percentage difference). Female respondents were more likely to report feeling hopeless, exhausted, sad, depressed, or suicidal. By comparison, an estimated 9.5% of American adults suffer from depressive disorders, according to the National Institute of Mental Health. Read more at Women in Astronomy.