Scientists are using brain imaging techniques, like positron emission tomography (called PET for short), to study the brains of human Methamphetamine users. They have discovered that even three years after long-time Methamphetamine users had quit using the drug, their dopamine neurons were still damaged. Scientists don't know yet whether this damage is permanent, but this research shows that changes in the brain from Methamphetamine use can last a long time. Research with animals has shown that the drug Methamphetamine can also damage neurons that contain serotonin. This damage also continues long after the drug use is stopped.
These changes in dopamine and serotonin neurons may explain some of the effects of Methamphetamine. If a person uses Methamphetamine for a long time, they may become paranoid. They may also hear and see things that aren't there. These are called hallucinations. Because Methamphetamine causes big increases in blood pressure, someone using it for a long time may also have permanent damage to blood vessels in the brain. This can lead to strokes caused by bleeding in the brain.