Friends of the comic, who starred in and co-wrote Gavin And Stacey with Mathew Horne, are worried that he is suffering from depression after taking some of the negative comments personally.
Their fears come despite the box office success of the duo's movie Lesbian Vampire Killers, which defied critics and took more than £1 million in its first week.
"It’s the first time since everything kicked off for him that the non-stop good times have really turned bad. He has been depressed because he feels it has all been a bit personal," a friend told The Sun.
"Other good news hasn't helped to pick him up either, and that has been a cause for concern among all his friends."