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24DESIGNER DRUGSand experiences very pleasurable feelings. These effects maytake longer (15 –20 minutes) to achieve if the drug is snortedor taken orally. Regardless of how it is taken, the effects ofmethamphetamine last anywhere from 6–24 hours (muchlonger than the effects of cocaine, which last 30–60 minutes).When people start to use methamphetamine repeatedly,however, its psychological effects start to change. Repeated usecauses tolerance to the psychological and physical effects of thedrug—that is, the drug becomes less effective each time it istaken, causing the user to progressively need more and more of itto achieve the same desired high he or she has become accustomedto. However, some repeated users of methamphetaminemay become increasingly sensitive (or “sensitized”) to itseffects. Repeated methamphetamine use can lead to “psychosis”(a lost sense of reality accompanied by hallucinations, delusions,and paranoia). A common delusion experienced by meth users isthe belief that their skin is crawling with insects (“crank bugs”),so users may frequently pick at their skin, causing sores to form.Repeat users also commonly experience insomnia, mood swings,and personality disturbances, and because methamphetaminesuppresses appetite, significant weight loss. Meth users mayalso become violent and aggressive, or engage in odd repetitivebehaviors, such as being obsessed with dismantling andreassembling cars or other mechanical devices.In addition to its effects on the brain, methamphetaminecauses dramatic increases in heart rate and blood pressure. Thisis because methamphetamine causes increases in the secretionof dopamine, epinephrine, and norepinephrine in the heart andcirculatory system, raising the user’s heart rate to as much as200 beats per minute (normal heart rate is around 70 beats perminute). Irregular heartbeats (arrhythmias) are also common.In addition, methamphetamine causes blood vessels to constrict,resulting in higher blood pressure in many parts of the body,including the brain. This “cerebral hypertension” eventuallycauses damage to the vessels, greatly increasing the risk for stroke