Some of the godliest people struggled with depression. Elijah was one of them. Whether Jesus, as "a man of sorrows and acquainted with grief" was ever depressed may be a matter of semantics.
Depression can come from various sources, IMO. Some people are genetically predisposed to operate in a mildly depressed state -- at least most of the time. Others rarely struggle with depression.
Genetics, body chemistry, anger, frustration, disappointment, sad circumstances, pain, stress, weather, unhappiness, sunshine levels....a lot of possible issues.
I consider myself "occasionally depressed but it is relatively mild," although it has not always been easy. But, like most pastors, I deal with people who struggle with more serious issues.
So how would you label your struggles with depression? A non-issue? An occasional problem The norm.
Select the answer that most closely resembles your experience. If you are both "mildly depressed as a normal setting" and are occasionally depressed, sometimes seriously," indicate the later. The more severe of two choices would be appropriate.
If you have never taken medication for depression, you can label your experience "mild."