Depression can last short periods or even longer periods than that. Nothing to be ashamed about; it happens and we to what we can to get by and move forward from there.

I personally wouldn't tell a job I have been depressed for 5 years though because there can be a prejudice or bias in your hiring even though it may have nothing to do with your work performance; I would tell them if they ask about the gap that, 'I took time off to address a medical issue and am ready to return to work.' I have a 10 year hiatus of not working due to my illness and when I went back to school and to work, this what was recommended to me by the employment and disabilities office, is a sufficient explanation and they cannot ask what was the issue. If down the road you run into issues that the depression impacts your work, then there would need to be a further discussion with HR or or boss to disclose it but not until then.

Also, lots of people are returning to work after being out for all sorts of reasons, education, raising families, caring for family members, medical issues, unemployment,... a gap in work history is not so uncommon these days. You are prepared with a good explanation for yours.

Good job on getting your cover letter done. Best of luck as you move forward in your hunt and be sure to take good care of yourself. You can do it.