I know this is very specific and probably not that many dramas exist that have it but could you recommend any dramas where the male lead suffers from post traumatic stress disorder?

Love Me if You Dare
When A Man is in Love
Return of Iljimae
D-Day
only PTSD, or are you also open to mental disorders caused by trauma but not explicitly classified as "PTSD" in the drama? If only PTSD, Juls gave you an awesome list!
Oh can you suggest any dramas dealing with other mental disorders caused by a traumatic experience? If yes, I'm open to it :)
Evil Minds
ST ~ Aka to Shiro no Sousa File
Gap Dong
Dr. Frost (not my favorite)
Man of Honor (the character In Woo)

from your PTW list:
Aozora no Tamago
Ouroboros
Hotel King 
Nodame Cantabile
Rich Man, Poor Woman
Chuno (aka Slave Hunter) - the lead character lost his nobility status and his first love.
Fermentation Family - the lead character was an orphan child and does not remember his child hood.

The only one I've seen when they specifically told us is 'Autumn's concerto'
It's Okay, That's Love.
Kill Me Heal Me
Hyde Jekyll Me
movie;
steel cold winter
bokura ga ita
pitch-black darkness

drama;
kurosagi
missing you

they all don't specificly say they have PTSD like mars or dday but they are being haunted by traumatic events from the past so I guess it's the same?
If I recall correctly the main lead in Secret garden suffers from PTSD. Although I am not sure that it is referred to as such, From what little I know it certainly appeared like that to me. Another one is Heart to Heart, in which both leads suffer mental distress but develop quite different symptoms post stress. And last but not least there is The Master's Sun, in which the lead character becomes emotionally detached and looses the ability to read after a horrific incident in his youth.

Just checked and saw that you have already seen both Secret Garden and The Master's Sun but thought I leave them on here just in case somebody else checks out this thread for PTSD dramas.
Cheer Up has some of those themes, but it's more hopeful.
Autumns Concerto (Kinda... more like tortured past, and amnesia which makes it worse)
Me too, Flower