“This Is 40” is every inch a Judd Apatow movie, from the pop culture references and potty mouths to the blunt body humor and escapist drug use. Like all the movies he’s directed it’s a good 20 minutes too long.

But within that affectionately messy sprawl lies a maturation, an effort to convey something deeper, more personal and more substantive. That goes beyond the casting of his real-life wife, Leslie Mann, as half of the couple in question, and the Apatow children, Maude and Iris, as the family’s daughters in this sort-of sequel to the 2007 hit “Knocked Up.”

As writer and director, Apatow seems more interested in finding tough nuggets of truth than easy laughs. Much of the banter between longtime Los Angeles marrieds Pete (Paul Rudd) and Debbie (Mann) can be very funny, but frequently it’s raw and painful as they have the kind of conversations about children, finances and sex that might make many people in the audience feel an uncomfortable shiver of familiarity.

The film takes place during the three-week period when Pete and Debbie are both turning 40. Birthday parties, fights about money, giddy getaways, school confrontations and awkward attempts at reconciling with parents are among the many events that occur during this vulnerable time of transition.

Although they would seem to enjoy a comfortable lifestyle, Pete wonders whether his passion project, the niche record label he founded, can survive. Debbie wonders whether either of the two young women who work at the cutesy boutique she owns is stealing from her. Pubescent daughter Sadie (a confident Maude Apatow) is wondering what’s wrong with her parents, while youngster Charlotte (an adorably goofy Iris Apatow) wonders what’s wrong with the big sister she used to know and love.

Debbie and Pete search for answers but eventually understand they must look inward and support each other. This sounds like a pat, feel-good realization but it doesn’t come easily. These are people who rarely handle things well, from a discussion with the middle school principal to a visit with an estranged father. (The terrific supporting cast features Albert Brooks as Pete’s dad and John Lithgow as Debbie’s.) Rudd’s puppy-doggish, everyman likability still serves him well after all these years, and while Mann is humorously sharp and sometimes a bit too screechy, there’s also more depth to her performance.

If “This Is 40” feels a bit unsatisfying at the end, perhaps that’s because it’s meant as an interlude, a snapshot, a moment in time as the title suggests. It’s the feel-bad comedy of the holiday season — and that’s what makes it good.