Justin Bieber's Anger Issues Are Getting Worse, Dr. Jenn Mann Says

Justin Bieber's anger issues are only getting more intense, and he doesn't have the coping mechanisms to deal with his rage ... so says prominent therapist Dr. Jenn Mann.

We caught up with the reality TV star in Los Angeles on Tuesday ... and, we had to ask her what she makes of this former child star going off the rails on social media -- and berating the paparazzi to boot.

Dr. Jenn says she's super concerned about JB's behavior ... especially his posts about substance use. Remember, Bieber hasn't been shy when it comes to posting pics of himself smoking.

And, it seems Dr. Jenn's sure Justin doesn't have any coping mechanisms of note to deal with the trauma he detailed in a recent IG post ... so, when it comes to anger management and therapy, she's telling Justin to "Never Say Never."

Watch both videos for her takes -- Justin's actions may also be harming his relationship with Hailey, Dr. Jenn adds ... and, she mentions the story about the Biebs telling his better half she'd never get a Vogue cover.

While the initial comment was already hurtful, ya gotta hear why even sharing the story has the "Couples Therapy with Dr. Jenn" host singing "Baby, baby, baby oh NO!"

We dove into Bieber's financial struggles, rumored drug use and rocky relationship with Hailey in our new documentary, "TMZ Investigates: What Happened to Justin Bieber" -- now available to watch on YouTube.