Stick and Pokes for is like stimming (find out more here). Given their even busy and anxious mind - possible related to their ADHD and autism - tattooing is when they find peace.
Stick and Poke / Hand Poke Tattoos are different to tattoos made with tattoo gun. Instead of a machine injecting the ink, the artist holds one single needle that they put into the skin, dot by dot. Thus, generally this form of tattooing necessitates more layers as the hand is slower than the machine that shoots dots at a rate faster than what the eye can see.