Tolerance happens when you no longer respond to a drug in the way you did first so it takes higher dosage of the drug to achieve the similar effect . The adderall and meth, are also affected. A high is caused by increased dopamine and peptide activity in your brains reward system. The user experiences a neuro chemical reaction when the high wears off as per experts at Tarzana Recovery Center. You are then drawn to the substance used again and again to seek better high which is not achieved as you develop tolerance.