This is why it is a mental illness.<quoted text>
That is one great way of seeing it. For myself, I often compare the religious to people who are in abusive relationships but stay because they think their abusers love them, despite evidence to the contrary.
But your analogy is better because the goal of the drug abuser is not attainable, and their high is only a temporary thing.
For the religious emotions to be enhanced, the cult member has to get sucked deeper and deeper into the cult, to get the same or increasing high.
This is why they are all on the road to fanaticism, one way or another.