From a neurological perspective, it's easy to understand the appeal of methamphetamine.
As the drug enters the bloodstream and begins to affect the brain, it triggers a neurological system designed to give pleasure for certain behaviors. The feeling is familiar and, in its own bizarre way, even natural. For a while.
People start using meth to feel good. They later use meth just to feel better, ironically trying to combat psychological problems with the very drug that caused the problems.
And eventually, almost all frequent meth users experience some physical and mental problems: Weight loss, skin lesions, rotting teeth, paranoia, sexual dysfunction, hallucinations, twitching and lethargy are among the known effects of the drug.
Because of their mental state, meth users also are more likely to have violent encounters with people they know, strangers and law enforcement, and are more likely to hurt themselves.
It all begins, as do almost all our emotions and sensations, with chemical reactions in the brain. Whether pleasure, excitement or fear, those sensations usually are the brain's natural reactions to natural stimulation.
Off balance
But when those feelings are triggered unnaturally, the brain is thrown off balance and sometimes tries to compensate in harmful ways, explained Dr. Richard Rawson, a professor in the department of psychiatry at UCLA.
As a result, the same drug that once caused excitement and a sense of clarity later causes lethargy and paranoia. What once brought happiness eventually brings a condition called anhedonia, or the inability to experience pleasure naturally. The stimulant that keeps users awake for almost a week eventually causes them to sleep for days.
Users, of course, do not crave the drug because of the bad consequences, which do not emerge immediately. They initially take the drug because it feels good.
"Methamphetamine creates a release of dopamine in the reward centers of the brain that allows you to feel pleasure," Rawson said about the drug's immediate effect.
Dopamine is a chemical that acts as a neurotransmitter, which relays nerve impulses to muscles, glands or other nerves. It also is called the brain's primary pleasure chemical because of its role in the reward center, a part of the brain that awards pleasant feelings for certain behaviors, such as eating or sex, which are necessary for survival and procreation.
Meth triggers a huge release of dopamine in the brain, magnifying about 10 times the pleasure it would normally deliver, Rawson said. Everyday events suddenly become exciting, and the world is suddenly a much more interesting place for the new user. The sensation can last eight to 12 hours, Rawson said.
Damage sets in
The brain's level of dopamine returns to normal as the drug wears off. Rawson said the trouble begins when the user tries to repeat that sensation again and again, draining the brain's dopamine reserve and damaging the body's ability to produce more.
Explaining it numerically, Rawson said to imagine a normal brain operating with a dopamine level of 10, while a frequent meth user's brain has a dopamine level of 8. Meth users in this state experience anhedonia, and they need another boost of dopamine just to feel normal again, Rawson said.
"You feel depressed, fatigued or just sluggish," he said. "So you need methamphetamine to kick in your dopamine again. You've created this vicious circle."
With the body's dopamine level diminished, a dose of meth does not deliver the same rush as the first use.
Addicts sometimes say they use the drug just to bring their energy up to a functioning level, and Rawson said some longtime users have told him the drug has lost all its pleasurable effect. They use it only for Pavlovian reasons, going through the motions from force of habit, he said.
But as some parts of the brain become numb to the once-pleasurable effects of methamphetamine, the temporal lobe actually becomes more sensitive to the drug, Rawson said.
Eventually, psychotic
An overstimulated temporal lobe can trigger a psychosis such as hallucinations or delusions. About two-thirds of meth users experience some type of psychosis, and Rawson said some become so sensitive to the drug that hallucinations become a regular part of its use.
In a combination that sometimes has tragic results, hallucinations can be accompanied by paranoia caused by the drug's effect on the amygdala, an almond-shaped part of the brain that has a large role in expressing fear, rage and aggression.
When stimulated, the amygdala creates a heightened sense of fear and anxiety, prompting a fight-or-flight response important for survival.
Triggering the reaction unnaturally creates an unfocused anxiety in meth users, Rawson said.
"You have this feeling of anxiety produced by methamphetamine, and you don't know what it's about," he said. "The feeling to the user is, 'Something's wrong, and I'm in danger. Why I'm in danger, I don't know.' It's sort of a feeling detached from cognitive reasoning. You're not afraid for any reason, it's just that the drug has stimulated your emotional anxiety."
Rawson said the drug's effect on the brain leads to paranoia in about 80 percent of meth users and often shows up within the first few months of using.
"In many cases, that'll be the cause of some of the violence associated with methamphetamine," he said.
Prone to violence
As an example, he said, if a man comes home from work and his wife has gone shopping, he may imagine she is cheating on him, so he beats her when she returns. In many cases, paranoia and delusions have led to homicide, he said.
Methamphetamine also suppresses brain functions found in the prefrontal cortex and the limbic system.
The prefrontal cortex is the more evolved part of the brain that controls rational thought and overrides impulsive behavior. The limbic system, sometimes referred to as the reptilian brain, controls emotions, hunger, thirst, sleep and other biological functions.
The stimulation of the drug also causes an increase in sexual desire in men and women, Rawson said.
"All the data we've seen on this shows people who take methamphetamine have more sex than those who don't," he said. "The cops that used to go out and busts labs, they'd say universally there was pornography and even people videotaping themselves."
But the drug also causes delayed ejaculation in men, which Rawson said can lead frustrated men to compensate with aggressive, bizarre and even violent sexual behavior. After excessive drug use, however, some male meth users have experienced sexual dysfunction, he said.
Meth mouth
Some chemical precursors used to make the drug can excrete through perspiration and damage the skin, but Rawson said most of the sores that appear on some meth addicts are self-inflicted.
The drug restricts blood vessels in the skin, which creates a tingling or itchy feeling. Meth users who are fidgety, sleepless and subject to hallucinations will scratch incessantly at the itch, sometimes believing they are feeling bugs crawling under their skin and picking their flesh raw until they leave open wounds.
"For some reason, men tend to scratch their arms and torsos, and women their faces," he said.
Finally, the drug can cause what has been called meth mouth, or a rapid decay of teeth. A combination of the drug's acidic nature and dry mouth caused by a lack of saliva leaves teeth vulnerable to decay.
Combined with poor dental hygiene and an addict's unhealthy diet of sweets, sustained abuse creates what dentists have called a perfect storm of oral problems, Rawson said.
