Just reading an article that speculated on impulsivity occurring from different mechanisms between ADHD and (this is pre DSM5) pediatric bipolar.
They proposed ADHD was a cognitive or top down impulsivity; someone cut the brakes. PBPD would be emotional or bottom up. Someone removed the spring from the gas pedal. Both result in excessive speed.
Could this explain apparent resemblance between autism and schizotypal personality disorder? During adolescent pruning there may be too much or not enough. I forget which was which but inflammatory markers were involved so probably autism had more pruning.
It also relates to ASD and OCD. Repetition to escape or to seek reward.
So the five trait model in the DSM5 appendix has lucidity (opposing neurotic in the CANOE model– notable as the “negative” trait.)