It’s because he doesn’t regulate his ADHD with medication. He constantly seeks dopamine hits. It’s part of the problem, if the low dopamine levels aren’t regulated properly with people like Josh, they’re predisposed to engaging in impulsive behaviour to constantly chase dopamine. They’ll usually prefer short challenges and big rewards because of the fixation on getting the dopamine hit as quickly as possible. It’s why people like Josh are predisposed to addiction, too. His self medication actually makes things significantly worse, because weed will decrease dopamine levels in your brain and play a significant role in fucking up your brain’s reward system. His alcohol addiction will produce similar effects along with being a depressant.