Robin Williams made no secret of his battles with substance abuse and depression. Still, the Oscar-winning actor's apparent suicide on Monday shocked fans and friends alike and left many wondering whether warning signs were missed.

Appearing Tuesday on Fox News' "Happening Now," addiction expert Joe Schrank argued such signs are often "very subtle and very nuanced," noting "it would take a highly trained and skilled clinician who was seasoned with many years experience" to spot them.

Even if such signs were picked up, psychologist Dr. Chuck Williams explained why treatment is often a long and complicated process.

"We're still mapping the interventions that would be appropriate to treat depression and we're even further behind when it comes to addiction," Williams said. "It's so bad that we're looking at actually making physical changes to the brain as a way to treat addiction because outside of that, we really don't have really good treatment or interventions for it."

Still, tragedies like Williams' death shine a spotlight on mental health issues in America and offer a chance for the public to begin a conversation with their own health care providers.

"We always check our physical health, whether it's cancer screenings or blood pressure," Schrank said. "We don't check our mental health, and that should be something that's done."