The former pacer, who turned 35 on Sunday, said he bullied himself into remaining normal even while he battled lows. "How have I got through to now without doing anything about it? It's different for everyone. But I think I bullied myself into doing things and trying to live 'normally'," O'Brien told 'Sunday Star Times'.
O'Brien said he first experienced depressive lows while representing his university team and continued to have the problem even while representing the national team.
"I'd just got back into the Test team after two-and-a-half years out of the mix, but for the first two weeks of our tour to South Africa, I didn't really leave my room. I was just too scared.
"I went and played cricket, went to training and did a bit of shopping. But most nights I'd eat by myself and order room service," he said, recalling the 2007 tour of South Africa.