As an exploration of post-traumatic stress disorder in US war veterans, the psychological thriller “Jacob’s Ladder” was ripe for an update. As a piece of enjoyable ’90s shock schlock, it maybe should have just stayed where it was.

The 1990 original, from director Adrian Lyne, starred a pre-“Shawshank” Tim Robbins as a Vietnam vet hallucinating his way through 1970s New York. Here, director David M. Rosenthal (“The Perfect Guy”) adapts the same screenplay with a necessarily new twist, but also a lower level of imaginative mental chaos.

This version’s Jacob (Michael Ealy) is a former Army surgeon who served in Afghanistan. He’s now married and a new dad, and working in an Atlanta VA hospital where patients are exhibiting strange psychotic symptoms. One vet claims Jacob’s late brother Isaac (Jesse Williams) is actually alive and living in the subway tunnels, sending Jacob on an underworld odyssey where he begins to experience his own worrying, demonic visions.

Lyne may have been a sexist sensationalist (so many writhing, scantily clad women, from “Flashdance” to “9 ½ Weeks” to “Fatal Attraction”), but at least the first “Ladder’s” Elizabeth Peña had some fun as Jacob’s saucy girlfriend Jezebel. Here Nicole Beharie (“Black Mirror”) has little to do other than furrow her brow as the protagonist’s concerned wife.

Ealy and Williams dig into their roles as the golden boy and the prodigal son, and every so often Rosenthal gets in a genuine scare. But as the plot moves forward, it loses interest in the metaphysical torment that made the original so gripping. The drug called “the ladder” remains, but now it doesn’t lead anywhere you’d be dying to go.