Efron is said to have secretly undergone a stint in a treatment facility five months ago, seeking help for substance abuse issues.
The 25 year old has yet to comment on the rumours, but Harden believes Efron's alleged bid to get clean could serve to inspire fans who are on the path to recovery.
Harden tells E! News, "In my opinion, Zac Efron is a total hero. Him seeking help encourages other people with addictive issues to seek help. It's brave of him.
"I think only a coward lives in denial, and he is not a coward. He's a hardworking go-getter and I love him."