Are there any highly credible sources for this correlation?
No data on pre-meds, but there’s plenty of data showing med students are at higher risk for suicide than their peers. (Some studies suggests med students are 3x or more likely to die by suicide than their age peers.) Suicidal ideation has been reported by as many as 56% of all medical students at some time during medical school school.
https://www.webmd.com/mental-health/news/20180508/doctors-suicide-rate-highest-of-any-profession#1
https://www.medscape.com/viewarticle/896257
From PubMed (peer reviewed studies)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6276609/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6398967/
Medical student suicide isn’t just a problem in the US; it’s a worldwide issue.