Warwickshire batsman Trott was right to treat his condition just like an injury, and seek medical help, said the PCA chief executive.
Australia batsman David Warner branded Trott "weak" and said England were scared of fast bowling as Alastair Cook's side lost the opening Ashes Test in Brisbane.
But Porter said those comments had no bearing on an illness Trott was already fighting.
He said: "This does require bravery, admitting to a problem very publicly and leaving a tour and team-mates, that's the brave thing to do.
"It would have been much easier in many ways to plough on, and not address the problem, and maybe that's what people would have done 10 or 20 years ago and we'd never have known why they performed badly.
"At least we've grown up to the point that people acknowledge just as you shouldn't play on with a knee injury you shouldn't play on with a brain injury - you should seek treatment and get yourself right for the future.
"This problem wasn't caused by an Aussie player sledging Jonathan on the pitch, or indeed by anything that was said in a press conference.
"This is a serious illness relating probably to chemical imbalances in the brain.
"So it's not something that's been triggered by a recent event.
"From a cricketing point of view we would want to give Jonathan and his family the time, space and privacy to get on and address the problem."
Porter said England will initially lead Trott's treatment, with the PCA ready to offer help at any stage.
Marcus Trescothick left England's tour of India in 2006 in similar circumstances, and Porter said the Somerset batsman's honesty in discussing that situation has helped cricketers confront mental illness.
He said: "It's ground we've covered before.
"We are in the position where we have a support network of medical professionals available, and normally it's accessed by players through our confidential helpline.
"Any player who is struggling with any kind of problem, whether mental illness, financial worries or anything else, can call that helpline and after an initial assessment what we do is to provide access to whatever is the most appropriate form of help or treatment.
"That's well-established, and we'll be working very closely with the ECB to ensure he receives the very best of care.
"In this particular circumstance, England have their own doctor and psychologist.
"So they are leading on the case at the moment and will continue to do so.
"They have been working with Jonathan for some time, and we will be available to provide whatever support is necessary through our network.
"Our experience says it is right to have people interacting with a doctor or counsellor who strikes the right chord for the individual.
"So it's not necessarily the first person they talk to, it's a question of finding somebody who is able to engage with them.
"Every case is different, we need to recognise that there is a wide spectrum of illnesses and problems that are experienced by people.
"In many ways cricketers are completely representative of society, they are just in a slightly odd life, in a bit of a pressure cooker.
"But they are no more or less susceptible to depression or mental illness than any other walk of life.
"One of the positives from our point of view is that we have had role models like Marcus Trescothick who have been prepared to speak publicly about their problems and that has made it easier for every successive player who has a problem to come forward and do so without feeling a stigma attached to it."
- Sports & Recreation
- mental illness