The 52-year-old has been seeking treatment at the Cirque Lodge in Utah since the end of August.
Representatives for the star had previously refused to disclose the reason for her stay, but Spanish actor Banderas has now spoken out, admitting she turned to professionals in a bid to prevent a relapse into the narcotic addiction she suffered from for years.
Griffith battled alcohol and drugs in the 1970s and ‘80s, and spent time in rehab in 1998 and again in 2000 in an effort to kick an addiction to prescription painkillers.
The Shrek star has also used the opportunity to dismiss reports that his marriage is collapsing under the strain of Griffith's troubles.
He tells talk-show host Ellen DeGeneres, "Let me explain to you. It was actually in some magazine that I said that I gave an ultimatum to my wife. That I present the matter of divorce (sic) because she has been involved in addictions and blah, blah, blah...
"Melanie has been addicted for many years and we always came out. We said it out loud. It was OK, we were never embarrassed of the situation but... she was clean and sober for six years."
However, Griffith felt her resolve weaken after three operations on her knee following a skiing accident at the start of 2008 and feared taking the medication she was prescribed to numb the pain would tempt her back onto harder drugs.
Banderas adds, "In March, she came to me and said, 'I'm feeling a little bit weak in my determination for this (to stay sober)... so I just thought to go to rehabilitation by myself.'"
Griffith has her whole family behind her in her battle to stay clean -- and her relatives even attend group therapy sessions with the embattled star.
Banderas says, "We have been following some type of therapy with other families. There are a number of invisible heroes working in AA (Alcoholics Anonymous) all around the world. I just say to families, 'Don't get embarrassed, just confront this problem head-on. And don't hide from that because there is a beautiful gift at the end of this tunnel, and it is the person that you love back, and that is what I am searching for.
"So the whole entire family is supporting her, and I am supporting her, and at this particular time more than ever. I'm very proud of her."
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