Does methamphetamine use cause Parkinson's? And what do pizza boxes have to do with it?

The South Australian government is planning to roll out a new mass media campaign about the impact of using methamphetamine, including crystal methamphetamine or “ice” and powdered methamphetamine or “speed”.

The campaign includes warning messages on pizza boxes – presumably because young people are the group most likely to try methamphetamine and they also eat lots of pizza.

It’s based on research from a few years ago that links illicit use of methamphetamine and Parkinson’s disease.

The researchers looked at changes in parts of the brain after methamphetamine use and say they look similar to those in Parkinson’s patients.

But what does the research really tell us about the link? And will pizza box messages prevent these types of harm?

Read more: What is methamphetamine or 'crystal meth'?

Is there a link between methamphetamine use and Parkinson’s?

Parkinson’s disease is a brain disease that progressively gets worse and has no cure. The key feature is deterioration of neurons that manage the amount of dopamine in a part of the brain, called the substantia nigra. Symptoms start to show when about 50% of the neurons have been damaged.

This part of the brain is responsible for controlling movement as well as the production of the neurotransmitter dopamine.

Dopamine is the feel good neurochemical and part of the reward pathway in the brain. Every time we do something pleasant – like eating, sex, listening to music – our brain releases a little bit of dopamine to make us feel good and remind us to do it again. Dopamine is also needed for lots of other functions including thinking and moving.

Methamphetamine triggers the release of much larger amounts of dopamine than most other activities, which is where its intense pleasurable effects come from. But over time, with regular methamphetamine use, the brain’s receptors become less sensitive. Tolerance results. Then the effects of the drug are not as strong, or you need to use more to get the same effect.

We already know regular methamphetamine use causes changes in brain structure (what the brain looks like) and function (how the brain works). And that those changes are similar to those seen in Parkinson’s patients.

But as far as we know, unlike Parkinson’s Disease, the changes after using methamphetamine are temporary and in most cases the brain resets itself back to normal functioning once use stops or becomes less frequent.

Is the link a causal one?

A number of animal and human studies have shown a link between people who have a history of methamphetamine use and the later development of Parkinson’s disease in older age.

Studies have shown that people in treatment for methamphetamine problems are up to two to three times more likely to develop Parkinson’s disease.

However, it’s hard to work out whether one causes the other because the numbers of people with both methamphetamine use and Parkinson’s disease are very small.

The estimate of methamphetamine use is around 1.3% of Australians), and the number of people who develop Parkinson’s disease (around 0.1% worldwide) is relatively small.

The large majority of people who use methamphetamine generally use only a handful of times a year and for a short period in their lifetimes. So even if there is an increased risk of developing Parkinson’s disease, the population risk is quite small.

Studies like those from the UniSA researchers, that take a snapshot in time and look at the correlation of two events, aren’t able to tell us whether one thing causes another, only that they are related in some way.

So we don’t know whether methamphetamine causes Parkinson’s disease.

To really work out whether methamphetamine use causes Parkinson’s disease a longitudinal study is needed. A longitudinal study would track people from say childhood to older age and measure their brain structure and function over time to see whether there is higher rate of Parkinson’s disease among people who have used methamphetamine compared to those who haven’t.

Other potential explanations

It’s possible that short term brain changes from using methamphetamine have some longer term impact that make someone more vulnerable to developing a range of disorders later in life, including Parkinson’s disease.

But there may also be other explanations for the link.

Read more: Why do many people with Parkinson's disease develop an addiction? We built a virtual casino to find out

For example, people who use methamphetamine regularly are more likely to have poor nutrition (because the drug reduces feelings of hunger), more likely to have experienced trauma, and are at higher risk of physical injury. These factors might affect the brain in ways that make the development of Parkinson’s disease more likely.

Genetics plays a major role in Parkinson’s disease and also has some role in the development of drug problems. So there might be a common genetic link.

It’s also worth noting that other drugs, including alcohol and a range of common prescription drugs like medicines for treating psychotic disorders, depression, high blood pressure and epilepsy, also increase the risk of Parkinson’s disease.

And the pizza boxes?

We know mass media campaigns for issues that affect a relatively small number of people are not very effective. Targeted campaigns for people at risk of developing problems tend to work better.

Drug use is one of the issues for which public campaigns are largely ineffective. In fact, they can actually increase problems by creating stigma. This makes people less likely to seek help for their drug problems.

So the pizza box idea is unlikely to have much impact at all.

Money wasted on these types of campaigns would be much better spent on evidence-based interventions. These include addressing the social problems that increase the risk of using methamphetamine such as poverty and childhood trauma, effective drug education programs at school, harm reduction programs and treatment.

Read more: Parkinson’s disease: bad dreams could be an early warning sign – new study

If you are worried about your own or someone else’s drug use you can call the National Alcohol and other Drug Hotline on 1800 250 015 for advice, counselling or help finding a treatment provider.