Child neurologist here.

Definitely NOT bi-polar. He has never had a truly maniac episode (mandatory for diagnosing bipolarity) not even euphoria. Examples of maniac episodes would be killing Gaz while laughing, or charging the Parshendi alone, unarmed and unarmored.

I also strongly doubt if it can be classified as depression; it would be hard to truly assess due to him being in a truly terrible situation, finding a way to survive. To classify for depression you need to have some degree of anhendonia (not enjoying things you used to like), changes in appetite, sleep pattern, etc, in an otherwise “normal” life. To put it as simply as I can, even if my psychiatrist friends don’t fully agree, it’s not depression if you have an actual reason for feeling that way, i.e: finding a way to stay alive as a bridgeman. Renarin is more likely to suffer from real depression than Kaladin.

I also don’t believe he has PTSD since he (as of early RoW) doesn’t wake up with nightmares, has no flashbacks (remembering stuff and thinking you’re back in it), fear, irritability, hostility.

My opinion is that he has adjustment disorder (https://emedicine.medscape.com/article/2192631-overview). In adjustment disorders you can develop both depressive symptoms (not depression itself) and anxiety, insomnia, etc. Adjustment disorder usually resolves at around 6 months after the stressor events, and IIRC by OB most of his symptoms from WoK are gone.

Perhaps he is developing generalized anxiety disorder as of early RoW: not sleeping, always wondering what could go wrong.

I’m going to try and see if I can re-read WoK and make a deeper analysis into it.

P.S. Shallan (WoR) has dissociative amnesia first (flashbacks), and then multiple personality disorder (present day and onwards). Dalinar (OB) had some type of personality disorder (previously known as psycopathy), which included his alcoholism; before being magically cured of it by the Nightwatcher<! . Gavilar (OB & RoW prologues) >!also some type of personality disorder.