Using Meth Increases Risk of Developing Parkinson’s

Methamphetamine users are more likely to experience premature stroke, Parkinson’s disease, and parkinsonism, according to results of a recent study.

The study, “Methamphetamine and heightened risk for early-onset stroke and Parkinson’s disease: A review,” was published in the journal Experimental Neurology.

Increasing methamphetamine use is a growing global health concern, given the physical and mental harm associated with the illegal drug. Its use is known to cause damage to blood vessels in the brain and heart, and can lead to psychosis and suicidal tendencies.

Methamphetamine’s effects on the brain, in particular, have attracted researchers’ attention, as evidence from animal studies suggest that it causes widespread alterations in brain structure, including damage to dopamine-producing (dopaminergic) neurons, a hallmark of Parkinson’s.

Methamphetamine users tend be younger than 45 and less likely to seek medical help for non-emergency conditions. Developing conditions, therefore, may not be detected in a timely fashion and lead to worse outcomes.

Julia Lappin, PhD, and Shane Darke, PhD, with Australia’s National Drug & Alcohol Research Centre, reviewed studies on the occurrence and clinical features of stroke, Parkinson’s disease, and parkinsonism associated with methamphetamine use, looking for evidence of underlying disease mechanisms. Parkinsonism is any condition that causes a combination of the movement abnormalities seen in Parkinson’s disease.

Several studies linked methamphetamine use to both Parkinson’s and parkinsonism in general, with one large U.S. study showing a greater Parkinson’s risk among people who had been admitted to a hospital for methamphetamine-related issues. Another study estimated an up-to-three-times-greater risk of developing Parkinson’s among individuals who had been exposed to the drug.

Methamphetamine use also was reported to be associated with a six-year median earlier onset of Parkinson’s.

Lappin and Darke noted, however, that Parkinson’s remained rare among adults younger than 45 despite the higher risk observed in these studies.

The team suggested there also may be a subset of people particularly vulnerable to developing Parkinson’s following methamphetamine use. If so, then the factors underlying such susceptibility, whether related more to the individual or to the drug, remain unclear.

Although methamphetamine users showed subtle signs of parkinsonism, such as hand tremors, walking slowly, and difficulty with speech and posture, the relationship between these symptoms and the risk of later developing Parkinson’s remains unclear.

Lappin and Darke found that where brain-imaging data was available, methamphetamine users showed changes in the substantia nigra — a brain region where dopaminergic nerve loss often begins — similar to those of people with Parkinson’s.

However, with few neurological studies with which to compare the imaging data, the researchers could not determine to what extent methamphetamine use causes lasting and irreversible dopaminergic neuron damage. The team also noted that methamphetamine users’ higher mortality rate further complicates things, as Parkinson’s tends to develop later in life.

One interesting finding was that methamphetamine-related Parkinson’s and parkinsonism “may be less likely among those who smoke, as nicotine is a known protective factor in [Parkinson’s],” the researchers highlighted.

Finally, some studies showed evidence that methamphetamine use is associated with falling dopamine levels. While this could lead to a progressive loss of dopamine function, which raises one’s risk of Parkinson’s and potentially hastens its onset, “direct evidence of degeneration of dopaminergic neurons in methamphetamine users has not been demonstrated to date,” the researchers wrote.

Beyond Parkinson’s, the studies that Lappin and Darke reviewed indicated that meth use is a significant cause of stroke among users younger than 45, and is associated with significantly worse outcomes.

Overall, “methamphetamine use is associated with important neurological harms at a young age, resulting in significant disability and life years lost,” the researchers concluded. “Evidence from a variety of sources supports a link between methamphetamine use and increased risk for the earlier development of [Parkinson’s] and parkinsonism, at least in a subset of individuals.”