I have been doing some research on complicated grief recently. It seems that the term complicated grief is a reasonably new term and that the mental health bods are still working on a definition and what makes complicated grief different to normal or uncomplicated grief.
One of the most commonly used/said words when talking to someone who is grieving is that "time heals" (although it may not feel like it at the time). I realised though that sometimes time does not heal the pain of grief and that that in itself could be the difference between complicated grief and normal or uncomplicated grief. In normal uncomplicated grief time DOES heal but in complicated grief time DOESN'T heal
In complicated grief there may be a block or barrier to that healing taking place, so that you get stuck in the pain.