Short-term adverse effects include grinding of the teeth, blurred vision, sweating and a rapid heartbeat,[14] and extended use can also lead to addiction, memory problems, paranoia and difficulty sleeping. Deaths have been reported due to increased body temperature and dehydration. Following use, people often feel depressed and tired.[14] MDMA acts primarily by increasing the activity of the neurotransmitters serotonin, dopamine and noradrenaline in parts of the brain.[14][15] It belongs to the substituted amphetamine classes of drugs and has stimulant and hallucinogenic effects.[8][20]