I have a very good friend who is a therapist for an inner city school district dealing with very traumatic cases in teenagers and she swears by EMDR. It’s a process, and you have to believe in it yourself or you’ll never actually put in the effort needed to pull some of those memories from wherever you locked them away in your brain. Best of luck to your friend. Tell them to just believe in the process and be open to it all. Not sure how old he is, but I know the older generations have a little fear and skepticism towards any kind of therapy so it’s wonderful to hear that they’re taking the correct steps to try and get better instead of just trying to cope with what’s going on.
Edit: She also showed me a song by NF called “Mansions”. I’m on my phone so I can’t embed but here’s the link and some of my favorite lyrics in the spoiler that really resonate to me about locking memories away and how that affects your mindset later in life.
https://www.youtube.com/watch?v=uF5QE3-ox4o