There are three kinds of dead.
Physically dead: no heartbeat, no brain activity. Returning to dust.
Psychologically dead: no will to live, immobilized, depressed, incapacitated to one degree or another either physically or mentally, perhaps even vegetative. One can be physically alive, moving and breathing, going through the motions, spiritually acquainted with God, but emotionally miserable and tormented. One might as well be a zombie. Perhaps this is what has given us the sci-fi genre. What a terrible and sad way to live.
Spiritually dead: having suppressed or rejected relationship with the Divine. If one holds a biblical worldview, this is a fearsome prospect.
Of the three, I far prefer the first. (But only after I have fully lived the time God has intended!)
I have briefly experienced the verge of psychological sickness “unto death” and I certainly know what the spiritual death is, though being raised in the church and accepting Christ at a young age and growing in faith through the years has protected me from the risk of out and out spiritual death. And I know I will experience physical death unless Christ returns first. How sad that some people experience all three.