This is the film that answers the question we've all asked about sex addiction since Hollywood stars began telling all in gossip rag sob stories; does it really exist? Or, as pragmatic love interest Phoebe (Gwyneth Paltrow) ask hero Adam (Mark Ruffalo) when he finally comes clean about suffering from it, isn't it just an excuse for guys to cheat?

Whatever your views, Thanks For Sharing unashamedly believes in sex addiction as a modern and very real malady. As Phoebe also observes of Adam, being a straight, mature, single and gainfully employed New Yorker makes him almost too good to be true, and with strategies to combat his illness that include not owning a laptop and having porters remove TVs from hotel rooms, Adam's finally on the straight and narrow.

He does so with the help of his sponsor, former alcoholic Mike (Tim Robbins), and in turn sponsors fellow sex addict Neil (Josh Gad). All three are in a traditional 12-step program and things are going swimmingly until everyone's life is turned upside down.

For Adam, it's meeting the beautiful Phoebe, who seems to have her life even more together than he does despite her own history of illness after surviving breast cancer. Mike and his wife Katie (Joely Richardson) are surprised by the arrival of their grown, former addict son Danny (Patrick Fugit), who – as an addict himself – Mike has to learn hard to trust again.

And Neil is having trouble committing to the program until salvation beckons in the form of friendship with a new member of the group, fellow sex addict Dede (Alecia Moore, aka pop star Pink). When Neil and Dede are drawn to each other, they start to learn that relations with the opposite sex don't always have to involve desire and destruction.

As Adam falls deeper for Phoebe, his conundrum is whether to tell her about his condition – she says at the outset that after a former alcoholic boyfriend she wants nothing to do with addicts.

The plot tracks all three men and the women and families in their lives mostly in parallel, showing the effects of past mistakes that will never leave them truly alone them, all three stumbling badly on the same fateful night and their hopes for the future.

Even though he's great in the role, it's hard for Ruffalo not to rely on his crumpled charm only because his drawl and everybody's-buddy smile are so distinctive. Paltrow is a particular standout, giving Phoebe a knowing worldliness and sharing easy romantic chemistry with Ruffalo. Gad has his moments even though a lot of his character is comic relief, and Robbins shows the kind of gravity he's been growing into for years now. Moore is the biggest surprise because we've never seen her do this before, but she gives Dede a real dimension as the lost, scared girl who's all tough attitude on the outside.

The script and direction by writer-director Stuart (The Kids Are All Right) Blumberg is sensitive and heartfelt. Everyone – right down to the supporting cast – are given enough room to play real characters and you believe every word of what goes on, even if you think sex addiction is still an excuse for male movie stars to shag anything on two legs.