yes, it is, and I have gone through it(and still think I am in it)...I think it's because we tend to internalize our thoughts and emotions a lot, personally I tend to get depress easely...Maybe it's because sometimes I just feel like life is not worthed, that I hate being misunderstood..sometimes feelings of unappreciation really affect me, criticism and conflict also. the fact that I live a complete solitary life outside the internet does not help, as I think INFJ's enjoy time by themselves introspecting and imaginating, but there's a point where you reach your limit, you feel alone, lonely, unworthy, and misunderstood and that's when it hits you,, me at least. I also suffer from low self-confidence which also aids to this whole depression of mine, suicidal level? once in a while, but I usually get back to my senses after that day and move on..I just try to keep some sort of optimism that the next day will be better and things would change..