Depression is not being down or fed up. Of course a doctor is highly skilled at assessing for depression. He/she can use a number of standardised tests, ask the relevant questions and observe the persons demeanor.
May I ask what leads you to the assumption that " invariably" the patient leaves with a prescription. As for " swallowing these things" does this apply to other illnesses or is it just people with depression who have to ignore all that modern pharmacy can offer?
paying a teenager for watering