Methamphetamine causes the body to release large amounts of dopamine, a neurotransmitter, resulting in a prolonged sense of pleasure or euphoria for the user; however, over time, this causes severe side effects. With repeated use, meth depletes the brain’s stores of dopamine and actually destroys the wiring of the dopamine receptors. This is a major reason why users become so addicted to the drug; without it they are no longer able to experience pleasure (a condition known as anhedonia), and they usually slip into a deep depression. Although dopamine receptors can grow back over time, studies have suggested that chronic meth use can cause other permanent brain damage, such as declines in reasoning, judgment and motor skills.
In addition, meth is a powerful stimulant that causes the heart to race and the blood vessels to constrict, which can lead to a number of serious medical problems, including heart attack, stroke and even death. During these energy-fueled meth “runs,” which can last days, users generally exhibit poor judgment and dangerous, hyperactive behavior. For instance, many addicts have committed petty and violent crime when high on the drug, and even for casual users the drug can increase the libido and lead them to engage in risky, unprotected sex. Long-time users have been known to develop symptoms of psychosis, including paranoia, aggression, hallucinations and delusions.