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A Link Between Meth Use and Parkinson’s Disease

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A Link Between Meth Use and Parkinson’s Disease

Jan 09, 2015

A recent study published in Drug and Alcohol Dependence shows that methamphetamine users are more likely to get Parkinson’s disease than the general population. Senior author Glen Hanson, D.D.S., Ph.D., interim dean of the School of Dentistry and Dean of the Utah Addiction Center at the University of Utah, explains the reason behind the findings, and the implications for long-term use of other drugs, including prescription drugs.

Episode Transcript

Interviewer: A Link Between Methamphetamine Use and Parkinson's Disease, up Next on The Scope.''

Announcer: Examining the latest research and telling you about the latest breakthroughs, the science and research show is on The Scope.

Interviewer: I'm talking with Dr. Glen Hanson, Interim Dean at the School of Dentistry at the University of Utah and Director of the Utah Addiction Center. You've done some researching looking at a long-term and serious side effect of meth use. What did you find?

Dr. Hanson: We were interested in the dependence on drugs, such as methamphetamine and the amphetamines, and we knew -- we've known for quite a while -- that it interacts with that part of the brain that is associated with the neurological disorder known as Parkinson's disease. And from animal studies, our findings suggested that it may lead to Parkinson's disease in humans, and that's what the study looked at. We found that there was a connection between that dependence on these compounds and Parkinson's disease.

Interviewer: So meth use increases your risk for getting Parkinson's disease. How much of an increased risk do you see?

Dr. Hanson: In the general population, it's about a threefold increase.

Interviewer: This increased risk factor for getting Parkinson's disease is one of actually many terrible side effects of meth use.

Dr. Hanson: Correct.

Interviewer: And is this really the first long-term effect that we know of?

Dr. Hanson: It is, that has looked at a neurological piece to it. We know, in human studies, there are changes in some cognitive functions in people who are long-term users, and they find that some of these neuropsych determinants or elements are still compromised in these people, things such as memory. But even these studies typically only go out two or three years, and none of them have asked the long-term question, ''What neurological diseases may happen down the road to this population of amphetamine users?'' These studies are the first ones to show that this long term, maybe ten, twenty years after you've had the amphetamine problem.

Interviewer: So maybe we can back up a second and you can remind us what Parkinson's disease is.

Dr. Hanson: Parkinson's disease is associated with a fairly select group of pathways in the brain that are involved in motor control, and so some of the earliest signs of Parkinson's are things such as tremors, usually hand tremors, the way someone walks, their posture, they tend to become stooped.

Interviewer: And so you were mentioning in the beginning that there's a particular pathway in the brain that leads to Parkinson's disease. You've also shown that, at least in an animal model, that class of drugs can also damage that part of the brain.

Dr. Hanson: So this pathway uses a chemical called dopamine, and dopamine is a big player in mobility, in behavior, in movement. So there is a selected pathway called the nigrostriatal pathway that methamphetamine or the amphetamines damage when they're used continually and they're used in high doses. So the same pathway gets damaged in Parkinson's. A general figure is that if you damage 70% of that pathway, then you start to see signs of Parkinson's disease.
In everybody, that pathway deteriorates over their lifetime, but most of us die before we reach that critical 70%, so the disease doesn't show up. However, if you take a drug like the amphetamines and it pushes you down that pathway, 20% or 30%, that means you're more likely to hit that magic 70% plateau before you die, which means you're going to have Parkinson's because you got pushed down the pathway earlier on because of your drug use.

Interviewer: Getting this information out there, what do you hope that will accomplish?

Dr. Hanson: We would hope that it would educate the population that there are long-term consequences to misusing drugs in general, not just the amphetamines, but other drugs. As we start to discuss things about, "Do we legalize this? Do we legalize that,'' oftentimes we're not asking the long-term questions. We're asking short-term questions, but we don't say, ''Might there be something showing up in 20 years or 30 years?'' Here's Parkinson's, obvious, but what about other neurodegenerative diseases? May they also be linked? Something like Alzheimer's, may that be linked, and some of these other neurological consequences? So we probably need to be looking at that more closely than what we have done in the past.
Now, we focused on the abuse side. That takes you down the road of: 'Well, what about legitimate use, therapeutic use? Are there drugs we're using for long periods of time, and for good medical reasons . . .

Interviewer: Right.

Dr. Hanson: . . . but they may be doing things, should we look at some of these databases and see is there long-term neurological or psychiatric consequences to them that we're not seeing when we just do our short-term studies?

Interviewer: Right, and you did make the point earlier, when we were talking, that methamphetamines are actually in a larger class of drugs called amphetamines, of which there are many kinds, some of which are used under clinical supervision.

Dr. Hanson: Correct. Well, methamphetamine and amphetamine are prescribed. These are Schedule II drugs. But is there consequences? Is there just the dependence situation, where you're using large doses, and maybe you're binging with it and you're injecting it versus therapeutic doses, which are smaller, you're taking them orally, and we need to look at that. My inclination would be I think that there is a difference. Some of the studies we've done in animals say that the brain responds very differently when it's done with therapeutic caution versus when it's done with abuse abandonment, but we need to make sure that that's the case when we look into our human cohorts.

Announcer: Interesting, informative, and all in the name of better health. This is The Scope Health Sciences Radio.