The Duke of Sussex had a long convo with Dr. Gabor Maté Saturday, where they dove into his book, "Spare," and the benefits of Harry living his true, authentic life ... while breaking away from the Royal Family, which he says was holding him back from this for years.

During the chat, they talked at length about trauma, vulnerability, healing and why Harry was opening up as much as he is. For that last bit, PH actually calls all this (the book/press run) a service to others ... because he genuinely believes it'll help folks better themselves.

There were a lot of standout moments -- including the fact Harry insists he's not a victim, nor is he seeking sympathy here -- but one that truly flashed was when Dr. Maté diagnosed him right on the spot ... handing down disorders that he says he perceived from reading about Harry and talking to him too. Among them ... ADD, PTSD, anxiety and depression.

Much of it, DGM explained, stems from his childhood -- with the death of his mother being a main factor, of course. Harry seemed to accept Dr. Mate's diagnoses at face value ... even acknowledging that he'd been diagnosed with PTSD by his own personal therapist.

Another interesting tidbit ... Harry talking about his past substance use. He distanced himself from cocaine -- saying he felt no benefit from it -- but he did praise marijuana and psychedelics ... explaining that he felt both of those had helped him become more clear.

At one point, Harry also addressed the flak he continues to catch from the media and others for speaking up about his private life/woes -- in his mind, he actually thinks the criticism hurts more than it helps, because he says it discourages normies from opening up.

Harry also talked about his wife, Meghan Markle, and his kids. In terms of MM, he praised her as saving his life and helping him break free from what he essentially calls shackles of the Royal institution ... and when it comes to his kids, he says he's trying to heap on as much love and affection as he can, to compensate for what he says he lacked as a child.

Frankly, much of the conversation focused on mental health ... not so much on Harry's father or brother or any other particular Royal. But, there was a noteworthy revelation PH dropped -- he says when he was first getting into therapy, he actually encouraged his "family" to do the same ... presumably, that means he approached Will/Charles with the prospect. It doesn't sound like they took him up on it, though, and Harry says he believes it actually widened the divide between them. As he put it, therapy was both a blessing and a hindrance.

Toward the end, Harry fielded Qs from people who were watching ... none of them were all that profound or pointed -- most simply asked how/why Harry thought it was important to seek help ... and some of the most effective ways he thought folks could do that.

The takeaway ... Harry very much believes in his work to bring mental health awareness to the forefront -- and one of the vehicles he's using to do that is to put his own life and story on the dissection table for all to see. Not everyone may love it, but he thinks it's ultimately a good thing to lay it all out there ... even at the risk of further pissing off the Royals.

A few things that were NOT discussed here ... Harry and Meghan getting evicted from Frogmore Cottage (which they confirmed was happening this past week), King Charles' coronation, South Park making fun of them ... or next steps with the Royals at large.

Dr. Maté did somewhat allude to a controversy surrounding himself -- where he was accused of being antisemitic by some for his defense of Palestine -- and the guy made clear ... he comes from Jewish heritage and had family that lived through Nazi-occupied Europe. Without directly saying it, he seemed to suggest he wasn't antisemitic ... far from it, in fact.

All in all, it was insightful. And it's obvious Harry might keep on talking from here on out.