I’m a tenured faculty member with chronic depression. Even though one of the flare-ups was in my early twenties, I didn’t tell anyone in graduate school. Even now, when I’m relatively open about this, I have used the gloss of personal or family issues when going through particularly difficult times.
You should also not struggle alone. Your school should have mental health services. There may also be an ombudsman for student affairs. You may also find many of your peers also have mental health concerns. Create a strong support network for yourself.
Depression is a chronic condition. I’ve had several severe bouts through my 20 year career — and moments when the sun came out and everything felt great. I no longer hold the illusion that any sunny period will last and that I’m free of depression forever. The OP should also plan on what they will do if their depression is chronic, pharma-resistant, or remitting. That being said, I believe that some aspects of academia are good for people with depression (flexible schedules and being able to work from home for some of us) although there can be negatives as well (toxicity in some departments, incessant deadlines, stress before tenure, contingent employment etc.).