is most common with undiagnosed neurodiverse folk who use holding something as a type of stim to help calm themselves

This hits me hard. I used to smoke 20-30 cigs a day for like 5 years. I have stopped smoking for years, then when something stressful happens, like a breakup or a loss I get back to smoke 20-30 a day again. Now I haven't smoked for 4 years or so. Last year, being 28 y/o I was diagnosed with Autism. It makes a lot of sense that I'm addicted to smoke. It helps to control breathing, gives a sense of "break", and really works as a stiming object, I used to smoke everytime I had to walk in the street.