He has been hit with a two month ban and fined $A27,500 ($NZ30,000) for breaching Rugby Australia's illicit drugs policy.
Slipper returned two positive tests for cocaine taken from urine samples between February and May 2018.
In a statement, Slipper says he's been suffering from depression for a year, but in no way does it excuse his actions.
Rugby Australia Chief Executive Raelene Castle said: "We are extremely disappointed to be in this position today with one of our most senior international players having submitted two positive tests for cocaine.
"We are fully aware that James is dealing with very significant personal issues and we have been working with him since February on these matters. We are ensuring that James is receiving full help and support, including specialist medical treatment.
"James has expressed his sincere remorse for his actions and for placing himself, Rugby Australia and the Reds in this very difficult situation. It is an incredibly challenging time for him and his family and our immediate focus is on James' health and wellbeing while he undertakes an enforced period away from the sport."
Slipper has played 86 tests for the Wallabies, but his last match was in December 2016.