Is it true that religion was once classified by the American Psychiatric Association as a mental disorder?

was and still is read some text of the early 60s

Yes and still is. If only one person held these variety of religious beliefs, it'll all become too apparent. Talking snake, flying to heaven, eternal torture (by a "loving God"), angry God drowns the whole world (including children), but saves animals, walking on water, turning water into wine, having a relationship with the creator of the known universe, rising from the dead, talking to an invisible being (ie, Jesus), thinking God answers your prayers while millions of kids are dying from starvation, etc.

It's called being delusional.