I've spent eight years researching the relationships parents have with their children once they're adults. That's the topic considered in this film: 30-year-old Jeff (Jason Segel) is still living at home with his mother Sharon (Susan Sarandon), who worries about the fact that he smokes a lot of dope and won't get a job.

It's incredible, really, that so little academic research has been conducted into the growing phenomenon of young people moving back home. I call it "second-phase parenting" and, in my job, I see many such families who are looking for guidance. In one case, a son living at home had been sacked from his job after testing positive for drugs. His parents didn't even know he was a user.

The media paints an endlessly negative picture, calling them the "boomerang generation" and implying that the parents should really just throw them out. That's very much the view taken by Sharon. "Get your ass off that couch," she says to Jeff, "or find somewhere else to live."

If Jeff and his mother came to see me, I would say that what they really need to work on is not making Jeff get a job or move out, but on Sharon's under-negotiated relationship with her sons: she has to learn to accept them as adults. I don't subscribe to the blame culture that implies such children are somehow failures. If your relationship with your family is good, why shouldn't you live with them? The key thing, however, is for parents to move into second-phase parenting, to enjoy their adult children, rather than treat them as if they're in an extended adolescence – which is exactly what's happening here.

I would have liked to see a fuller depiction of the family's relationships: the script was quite thin, and elements of the plot verged on the preposterous. I won't give away the ending, but let's just say that Jeff gets to prove that he's loving and protective. Perhaps he and Sharon will learn to live together as adults after all.

• Dr Myrna Gower is a research fellow at Royal Holloway, University of London