One of the biggest (yet also most hidden) causes of depression for INFJ personality types (and INFP personality types) is blocked creativity. Many INFJ personality types do not even realize that the reason they feel low-grade depression constantly throughout their life is because they have cut themselves off from a vital need of their personality, and that need is the call to be creative.
Creativity is an unstable energy by nature, and because of its instability it can feel difficult for INFJ personality types to trust it. An INFJ who has experienced trauma in their past will most likely have control issues, and they will feel very uncertain about allowing creativity into their lives because the energy of creativity cannot be predicted, and it cannot be controlled. Surrendering to their own creativity can feel scary, and the INFJ personality type also doesn’t want to get hurt. So, they mentally protect themselves from feeling out of control by suppressing their own creativity.