A college student is brought to the campus health center by their roommate. The roommate reports that the student has been complaining of a constantly racing heart and nausea for the past few days. The student also seems unusually agitated and has expressed intense, unfounded fears that their professors are plotting to fail them. Based on this specific combination of physical and psychological symptoms, which category of psychoactive substance is most likely responsible? Explain your reasoning by linking the reported symptoms to the known effects of that substance category.