Columbia University psychology professor Andrew Solomon wrote his best-selling book—as he explains in the initial segment of the documentary Rachel Dretzin and Jamila Ephron have based on it—to come to terms with his late mother’s hostile attitude toward his coming out years ago. How, he asked, do parents react to children who prove very different from their hopes and expectations? And how should they?

No film of “Far from the Tree” could mirror the breadth and complexity of Solomon’s mammoth study, and Dretzin and Ephron’s doesn’t try. What it offers are a few case studies to illustrate its basic theme. Most are rather touching, even uplifting. But one, it must be said, raises some serious questions about the central argument.

After Solomon’s personal introduction, “Tree” turns to Jason, a forty-one-year old man with Down Syndrome, and his loving mother Emily, who along with her late husband raised him as much as possible as a normal child before his learning difficulties became apparent. The two are clearly close—she even puts up with his obsession with the movie “Frozen”—though there are moments when Jason’s brusque behavior obviously hurts her.

A second subject is Jack, an autistic teen who at first seemed unable to communicate; it was by accident that it was discovered that he could do so not through speech but writing, and he is now equipped with a computer system that allows him to. He also socializes with friends with similar conditions (just as Jason does). Still, his mother questions whether if had she taken better care of herself during her pregnancy, her son might not have developed autism.

The film then takes up the example of Loini, whose life with dwarfism is a lonely one until she’s persuaded to attend a Little People of America meeting, where she’s liberated by the camaraderie. There we also encounter Leah and Joe, who met one another at a previous convention, became romantically involved and are now trying to have a child. Naturally they wonder whether, if they are successful, the child will be like them.

The final subject is the outlier among the group, a young man named Trevor Reeves who murdered an eight-year old boy walking along a nature path when he was sixteen. The subsequent trial, along with the comprehensive psychological examinations that accompanied the case, revealed that though he seemed very well-adjusted, Trevor had long harbored thoughts of killing someone, a fact that shocked his mother and father. The emphasis here is on how his family have reacted to his inexplicable crime; his parents and siblings cannot understand how the boy they knew and loved did what he did, and they grapple with the possibility that some genetic abnormality might have been involved.

That case fits with the film’s emphasis on how parents deal with children who have fallen “far from the tree,” as the title indicates. But it’s hard to avoid thinking that in some fundamental way it’s very different from the others, involving a choice which might be inexplicable but was still a choice. That’s certainly not the case with Down’s syndrome, or autism, or dwarfism; and while some biological factors could have been involved, there’s no evidence to prove that. As such this final segment seems somewhat out of place in this context—as though it had wandered in from an episode of one of those ubiquitous TV true-crime shows—though one can certainly understand the filmmakers decision to include it.

One thing’s for certain: Trevor’s story certainly doesn’t allow for the suggestion of inspirational uplift that marks those of Jason, Jack, Loini, Leah and Joe. In this case there is only the heartbreak of the families of both the killer and his victim.

“Far from the Tree” is a worthy cinematic attempt to reflect the theme of Solomon’s book, even if it inevitably feels like the Reader’s Digest condensed version.