You may wish to look at other recent threads on the “dark night of the soul.” There have been a couple.
The “dark night of the soul,” a phrase of St. John of the Cross, has nothing to do with depression. Depression is an emotional, mental, and/or physical state that can be helped by therapy or drugs.
The dark night of the soul, as John elaborates in his book by the same name, is a spiritual state of high holiness, when God removes all palpable sense of his presence from the soul, plunging it into a state of longing for God while feeling utterly cast out of his presence. It is similar to Jesus’ cry on the cross: “my God, my God, why have you forsaken me?” In allowing souls who are reaching sanctity this painful period, God refines faith, hope, and charity so that they are purified and greatly strengthened.