Music icon John Mayer, renowned for his soulful melodies and captivating guitar riffs, is on a mission that's about more than his music. When he's not making music, he's focused on the mental health of veterans.

For over a decade, the seven-time Grammy winner has been quietly pursuing research into veterans' mental health issues. Several years ago, in 2019, he launched the non-profit Heart and Armor Foundation with $3 million of his own money, funding studies that look at issues like the effect of trauma on women warriors, and the biology of PTSD.

"That's a burden that I think we can help lift off of people," Mayer said. "Someone saying that the smell of diesel fuel at the gas station triggers a very anxious response because it's a sense memory from Iraq or Afghanistan. And that got me deeper and deeper into wanting to understand it."

Money raised since then — including half a million dollars from a recent intimate show with Ed Sheeran — has helped publish 25 peer-reviewed studies.

Mayer's connection with veterans began in 2008 with a visit to Marine Corps base Camp Lejeune and came after years of success that left him wondering what else he could do for the world. The stories he heard — and the veterans he met — pushed his desire to make a difference.

"It was not set up as a celebrity visit. So, they didn't know I was coming, but it was the most natural way to meet these veterans, and just immediately start talking and hearing their stories," he said. "The humanness of it is what struck me."

Heart and Armor's work includes community outreach and supporting veterans like former Army Sgt. Aundray Rogers, who witnessed unthinkable horrors in Iraq in 2003. Once home, he couldn't cope and said he struggled with alcoholism, substance abuse and suicidal thoughts. He said he never thought he was suffering from PTSD.

"After seeing just a lot of bodies, you know, people on fire, cars burning with people in them, in buses. A small-town boy from Mississippi, I wouldn't have never thought I'd see something like this," said Rogers.

With the help of Heart and Armor, Rogers has moved from being homeless to healing. He is now a volunteer helping others.

"It means so much, that insurmountable support that they give me to serve. You know, service is my medicine," said Rogers.

The essence of Heart and Armor is perhaps best seen when Mayer meets with the organization's volunteers, like former Marine Spencer McGuire. McGuire said Mayer's album "Continuum," particularly the songs "Waiting for the World to Change" and "Gravity," provided comfort during his service in Afghanistan, where he faced constant mortar fire and developed PTSD. 

Specific lyrics from "Gravity" — "keep me where the light is" — resonated so deeply with McGuire that he got them tattooed on his arm.

"My mom always kind of spoke to me about how it's really important to stay within the light. You got to fight for it, sometimes the darkness can be overwhelming, but you know, if you persevere, then you can get there," said McGuire.

 At 46, Mayer's definition of success has evolved. He said it's no longer about album sales or fame. 

"It's just down to touching people with music, getting people through tough nights with your music," Mayer said. "From this point until my last breath, we do this as a calling."

Jamie Yuccas

Jamie Yuccas is a CBS News correspondent based in Los Angeles.

Twitter