I’ve had friends who believe in ghosts, friends who don’t believe in ghosts, friends with an “open third eye”, and friends with a “closed third eye”. I myself believe in ghosts but haven’t seen one or sensed the presence of one. We have all dreamt about dead persons or pets interacting with us. A few grief-stricken friends have dreamt of recently deceased loved ones. I’ve dreamt of a grandfather I only know through my mother’s stories. As we think about those experiences, we realized that none of the “ghosts” we encountered in our dreams ever said or did anything that we didn’t already know either through first-hand knowledge or through intuition.
So while ghosts may try to communicate with us in our dreams or through our dreams, at least in my experience there are wholly rational explanations for why this would not be the case even if it seems to be so.
None of which stops me from laughing out loud at my favorite anime episode:
Yusuke Urameshi (green), the leader of a gang of misfits at a local high school, died recently after saving a child from being hit by an oncoming car. The Spirit World offered him a chance at resurrection, but they were unimpressed by everything else on his record before his heroic death. They said he had to demonstrate further his capacity to do good before being allowed back into his apparently unembalmed body, which was being preserved by magic or something. (It’s been decades since I've seen the episode. Back off.) Here we see Urameshi coaching his foil, comic relief, and best friend Kazuma Kuwabara (purple) for an upcoming exam in a dream.
The writers of Yu Yu Hakusho made it very clear that Urameshi’s ghost did indeed invade Kuwabara’s dreams all of his own free will in order to impress the Spirit World, and in order to prepare Kuwabara for his test. From Kuwabara’s point of view, however, nothing that Urameshi coached him on in their dream sessions was beyond what he’d already read on his textbooks. And why Urameshi? Grief, probably. It’s been only a week since his best friend died.
In the end, I don’t think ghosts communicate with the living any further beyond the grave because they can’t be bothered to. I believe there is a liberation from all of life’s concerns when a person shuts down for the last time. The dead would know this, if they ever know anything, and to them all of life’s little worries are over in a few decades. These worries and the trouble we assign to them dwarf to insignificance in the context of eternity, which is set before all of us, whether dead or living.
But hey, I'm not an expert in any of this. If you don’t understand what I’m saying, I leave you with another picture of Kuwabara and Urameshi which I'm sure you would understand perfectly well.
Source: My Quora answer to: Do ghosts try to communicate to us through our dreams?