The Good Vibrations hitmaker has been struggling with schizoaffective disorder for several years and he alternates between good and bad days.
He tells People magazine, "On my good days I feel creative, I laugh a lot, I go to my piano and play. Some days I don't feel creative and I don't talk to anybody."
But his wife Melinda insists the 70 year old is doing well - thanks to periodic visits to a specialist to talk through his issues, admitting he sometimes suffers from auditory hallucinations.
She continues, "He hears voices. I can tell if it's good voices or bad voices by the look that comes over his face. For us it's hard to understand, but for him they're very real. I have to bring him back down to reality and say, 'They're not real; they're not going to hurt you.' And then he'll say, 'Yeah, yeah, I got it.'"
Melinda reveals his struggles haven't affected his relationship with his seven children, adding, "The kids understand that he's a different kind of daddy. (But) he's an amazing dad in the respect that he absolutely knows everything that's going on."