Starring Mark Ruffalo and Zoe Saldana. Rated PG.

Sometimes, when filmmakers are too close to their subject, the results can involve serious TMI. While a worthy effort on several levels, Infinitely Polar Bear suffers from the opposite problem: its characters and situations too often feel superficial and sanitized, and we never really get under their skin.

In real life, first-time feature director Maya Forbes and her sister China—lead singer of cabaret jazzers Pink Martini—were raised by their father, a Boston blueblood with chronic manic depression, while their multiracial mom pursued an MBA and a Wall Street career.

Diagnosed as bipolar back when that was a new concept (hence the kidbookish title), Mr. Manic (a plum role for Mark Ruffalo) indulges in rants, tantrums, and happy revelations that come off like the performance art of an oversized child—albeit one who chain-smokes and drinks to excess. In other words, almost all we get is the up stuff, with an emphasis on cute eccentricity.

This fits with what a child might remember, or perhaps want to remember, and the fine actors here make a convincing display of this unusual family dynamic, even if the cycle of bust and boom (with a lot of yelling in public) grows repetitive.

A layer of additional discomfort comes from the fact that the director’s character is played by Imogene Wolodorsky, her own daughter with frequent screenwriting partner Wallace Wolodorsky, also seen in a small part here. The younger child (newcomer Ashley Aufderheide) seems less anxious, and one of the few conflicts we witness between sisters is connected to the difference in their ethnic appearance. In this area, too, the film stays on the surface regarding issues of gender and race, preferring jokey deflection to anything that might remind us of what has and hasn’t changed in the last four decades.

In those intervening years, the Forbes father died of cancer, the mother had a successful trading career, and how the girls felt about either remains unknown. It’s clear, though, that they both turned their experiences into art. Or, in this case, therapy.