As usual, I'm going to give a caveat Mom and I have been differing on for a long time. First of all, a general practitioner is not trained in diagnosing depression. They do study mental illness a tiny bit, but depression is a major mental illness that can only be diagnosed by an expert. General docs are not experts in much of anything, as they have to do so much in our system of medicine in so little time. It takes a fair amount of time talking to diagnose a mental illness as opposed to feeling sad or feeling grief or having a bad spell. A first appointment with a psychiatrist is generally 45 minutes. All appointments with a psychologist are 50 minutes or more. Appointments with a general doc are 15 minutes of actual treatment unless you're very wealthy and have a concierge physician who takes time or see 0ne who practices integrated medicine, neither of which take insurance. Psychologists spend the most time of any other professional studying psychology. Psychiatrists study a few months. Regular docs a mention in a textbook. Everyone gets to decide for themselves but before you get treated for depression you have to get a proper diagnosis. What your regular doc can do better is test you for a host of physiological problems that can mimic depression but aren't depression -- a psychologist can't do this and most psychiatrists won't. The other quibble is, "do I need medicine?" Need is a very strong word. Remember that when you mention medication to a doctor, you're very likely to get medication. That's mostly what docs do -- they really mostly don't know how to do anything else. They don't know how to do therapy -- psychiatrists know how to do it but usually don't, and even when they do, they give you less time and charge a lot more than a psychologist does with less training. What the psychiatrist has more training in than other docs or psychologists is medication, so before you ask these things of a doctor, ask them of yourself and your friends and family. How do you see you? How do they see you? How is your life going? Are you functioning alright or not functioning at all? In other words, do your homework before you see a psychiatrist, because medication is so overprescribed in the US it's become a national crisis. When you truly need it you need it, but if you don't, you might still end up with it, so be wary out there.
I would only like to add that sometimes a GP can do a good diagnosis. This requires a couple things that may not be very common but I wanted to put this out there. If you have seen the doctor regularly for years and they actually know you is #1. If they do doctors visits that are longer then 15 minutes. I agree that these in and out doctors visits aren't good for a diagnosis of a complex issue like depression. I believe if you have a long association with your doctor its more likely you can get a longer visit.
Ok, so assuming that happens and the doctor gives you a diagnosis of depression. Are they giving you a referal to a PDoc or going into see a therapist? If not I agree its less likely to be a good diagnosis. Just remember these other two people you will probably be meeting for the first time and I sometimes wonder if they are like hammers that see everything as a nail? Or in other words whatever symptoms you might have they try to fit it into some mental health diagnosis.
Its my experience that a GP that prescribes drug(s) for MI is going to be following up with you checking for side effects and if its effective or not. And I think for getting dose and drug right a GP might be a better situation then a PDoc you see once a year.