I'm also a medical student, and have heard the exact same things that the OP is describing during various lectures.
Regarding suicide, peer-reviewed mental health studies routinely show that firearms are statistically the most effective tool for suicide in America, with preponderance for the male population, usually elderly. Trying to refute this will ultimately be fuitile, and just make the pro-gun side appear to be detached from reality.
That being said, I really don't think you can make a rational argument for disarming the populace or further infringing upon a fundamental Constitutional Right based on potential for abuse by suicidal people. If guns were banned, because of this, eventually prescriptions for greater than 3-5 doses would have to be banned, followed by razors/sharp things, and bridges/cliffs. It could very easily be the case that the other methods of suicide would experience drastic increases in success rates following a gun ban. For example, females tend to be less successful at suicide than men, but female doctors are the most successful group when they decide to kill themselves. As a group, they overwhelmingly use prescription drugs and medical training to know exactly what dose to kill themselves with. As others have shown, other parts of the world experience higher suicide rates than the US, many of which have governments that ban firearms ownership amongst their subjects.
From my perspective, the mechanism by which a depressed person takes their life is irrelevant and purely an academic venue of research with no clear translational uses for the bedside. What is relevant would be the lack of adequate medical attention as well as support available to those that do kill themselves. It is often the case that elderly men, abandoned by their families/friends, who then develop depression exacerbated by somatic illness, kill themselves via firearms. Blaming the firearm demonstrates poor logical reasoning skills, or an interest to deflect criticism from the current state of psychiatric care.
