Your brain on drugs: It's not a normal brain
October 10, 2005 - registerguard.com
The senseless behavior of addicts makes sense to scientists who study the human brain.
The brains of addicts are different from normal brains, researchers say. The ways addicts weigh priorities and make judgments lead to decisions that neglect families, jobs and health - and that place continued drug use above all else.
Understanding addicts' behavior requires an understanding of how drugs react in the brain and how they change its chemistry, and how that changes behavior, says David Friedman. Friedman, a professor of physiology and deputy associate dean for research at Wake Forest University, is the founder of the Neurosciences Research Branch of the National Institute on Drug Abuse.
"The addicted brain is different than the normal brain. The evidence of that is now overwhelming," Friedman says. "Addicts who make these lousy decisions resemble people in many ways who are known to have damage in the prefrontal cortex, and because of that damage make lousy decisions.
"Classically, it's, `I shouldn't get high. I should go buy food for the kids.' Frequently, those people go get high. They can't make that good decision for the long term, instead of the short-term decision to get high."
Other examples are the addicted woman who can't stop using when she gets pregnant, and parents who can't stop even while their children are living in squalor.
"The reason they can't stop is the addict's brain is not like the normal brain. They are not as capable of making sound decisions as normal people are. Their decision-making capability is impaired," Friedman says.
While some brains become addicted to a drug after one exposure, all brains become addicted after repeated exposure. Recovery requires time for the brain to readjust - chemically and physically - to function without the drug, he says.
Although researchers are a long way from a complete understanding of brain chemistry and addiction, it's clear that drugs such as methamphetamine operate on the so-called "pleasure circuits" of the brain by increasing the release, or decreasing the absorption, of the neurotransmitter dopamine.
The more dopamine the brain senses, the more pleasure a person perceives - be it from eating, hearing music, seeing a loved one or taking meth.
What sets meth apart from other addictive drugs is that it both releases dopamine and slows its absorption, Friedman says. In effect, it is a double-action stimulant on the pleasure circuits, he says.
"It's more complicated than dopamine. That's part of the picture."
But one thing leads to another. The pleasure circuits are connected to the frontal area of the brain - the area where values are formulated, judgments are made and priorities are set.
Drugs such as meth overwhelm the pleasure circuits, releasing more dopamine than any normal human experience does. Meth use stimulates more meth use by boosting pleasure signals to the brain's judgment centers, warping its decision-making process.
The more the drug is used, the more the brain grows dopamine receptors to cope with the flood of dopamine.
A decision to stop using meth goes against strongly wired circuits in the addict's brain, where the overabundant dopamine receptors "cry out like deserted lovers for the missing chemical," according to Dr. Richard Restak, a neuropsychiatrist, clinical professor of neurology at George Washington University and author of 10 books on the human brain.
When breaking a meth habit, craving can last a long time while the brain physically adapts to operating without the drug.
"If the addicted person stays away from the drugs, the (dopamine) receptors eventually die off like leaves spiraling from the branches of a tree deprived of light," Restak writes in his book "Brainscapes." When the excess dopamine receptors are gone, the brain's natural balance returns and the craving for meth declines.
But heavy or prolonged meth use can push a brain past the point of no return.
"When those dopamine circuits get screwed up, that leads to psychosis," Friedman says. "Too much dopamine floating around makes people look like they're psychotic - hallucinations, paranoia, aggression.
"A lot of people use drugs and don't get into trouble," Friedman says. "Some people do get into trouble with them. The question is why. The simple answer is people get into trouble with drugs because of the way their brain responds to them. You don't have any choice about how your brain responds."
The ill effects of meth probably will play a large role in counteracting the current epidemic, just as in a similar meth epidemic in the 1960s, Friedman predicts.
"One of the reasons these epidemics die down is people see what's going on," he says. "What's going on now probably has a natural life cycle, like the flu. It's not going to ever go completely away, because there are always people who are willing to use."
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