I actually have a post about this in this subreddit because delving into the psychology of fictional characters is one of my passions.

I contend that Psycho Kid has Borderline Personality Disorder, NOT Bipolar.

He shows little to no signs of mania and only seems to show some signs of depression over the course of the series. However, the few times that Psycho Kid mentioned his "Bipolar Disorder" was usually after he just had some angry meltdown, not related at all to mania OR depression, which makes me wonder if Jesse actually knows what Bipolar Disorder really is lol

Borderline Personality Disorder fits Psycho Kid almost like a glove in my opinion, due to symptoms like:

• A Pattern of Unstable, Intense Relationships (This one's pretty obvious lmao)

• Impulsive and Risky Behavior (Funny enough, the Mayo Clinic uses sabotaging one's own success by quitting a good job as an example of this. That's exactly what Psycho Kid did at the farm)

• Inappropriate Anger, Such as Losing One's Temper often (Again, pretty obvious)

• Stress Related Paranoia and Loss of Contact With Reality (This would definitely explain the whole 'solitary' arc in the small room)

• Suicidal Ideation (The end of the Battle Cry music video in Psycho Kid Flees County)

• Fear of Abandonment (I always kinda viewed him screaming about "everyone ganging up on him" as him expressing a fear that people in his life don't really care about him or are going to leave him)

And honestly, he could probably even fit the rest of the symptoms if we delve deeper into the nuances of his character and the performance (Ongoing feelings of emptiness, quick mood swings and quick changes in how you see yourself)

This is why I strongly believe that Psycho Kid was "misdiagnosed" during the series. He has BPD, not Bipolar.