President Trump's Twitter Rants Show Narcissism and Lack of Impulse Control

President Trump's a child with extreme narcissistic tendencies ... so says "Couples Therapy" star Dr. Jenn Mann, who helped us psychoanalyze 45 ... in an attempt to figure out what's behind his brutalization of people on Twitter.

We got the good doc Thursday in L.A. and the TV/radio shrink has her own mental dossier on Trump's antics, and what's really behind them.

For starters Dr. Jenn says Trump is a walking dichotomy ... on the one hand he's like a young child lacking impulse control who gets triggered by just about anything critical of him or his job. On the other hand, he a master at manipulating and besting the media by creating diversions ... and that skill may be Trump's most powerful weapon in 2020.

The latest attack, as you know, is against 16-year-old Person of the Year Greta Thunberg, whom Trump tried to bully, but much to the delight of everyone, Greta clearly knows his game.

Dr. Jenn thinks Trump's playbook may have been set in stone while he was still a child. She says this could well be a case where the Trump family didn't set proper boundaries. Watch the video and see if you buy it.