Specifically the review which analyzed studies from over 43 countries revealed "the overall prevalence of depression or depressive symptoms among medical students was 27.2%, and the overall prevalence of suicidal ideation was 11.1%. Among medical students who screened positive for depression, 15.7% sought psychiatric treatment."
To learn more about the study, check out:
http://jamanetwork.com/journa…/jama/article-abstract/2589340
http://www.cbc.ca/news/health/medical-students-medicine-mental-health-depression-suicide-1.3883935