It’s no secret that illicit substance use, or substance use disorders, can cause a variety of health effects, including increased risks for certain diseases. As Parkinson’s News Today recently reported, one medical study connected methamphetamine use to an increased risk of Parkinson’s disease (PD/Parkinson’s), parkinsonism, and stroke. Since rates of methamphetamine harm are rising, it is important to better understand this association and improve public health. Check out the full study findings published in Experimental Neurology.

Methamphetamine

According to the CDC’s Morbidity and Mortality Weekly Report from March 27, 2020:

Methamphetamine is a highly addictive central nervous system stimulant. During 2015–2018, an estimated 1.6 million U.S. adults aged ≥18 years, on average, reported past-year methamphetamine use; 52.9% had a methamphetamine use disorder, and 22.3% reported injecting methamphetamine within the past year.

Typically, methamphetamine users are younger in age (under 45). Because they are less likely to go to the doctor or seek out assistance, especially for non-emergency issues, potential health problems are not often caught early. Additionally, methamphetamine usage is often seen in conjunction with other substance abuse disorders or mental illnesses. Although the CDC explains that (technically) usage rates have remained fairly standard, there has been increased availability and related health harms, such as overdoses and deaths; psychosis; transmission of infectious diseases; and issues with cardiovascular and renal function.

The Research

Within this study, researchers wanted to understand the intersection between methamphetamine and brain function. In prior animal studies, methamphetamine changed the brain structure and damaged dopaminergic neurons. Since PD is also characterized by dopaminergic neuron death, researchers wondered if methamphetamine use could heighten PD risk. To begin, Dr. Julia Lappin, PhD, and Dr. Shane Darke, PhD, read and evaluated past studies on stroke, PD, and parkinsonism (any condition causing the movement-related symptoms associated with PD) in relation to methamphetamine use. Findings included:

• Patients with methamphetamine use disorder experienced PD onset around 6 years earlier than those who did not use this drug.
• In one study, data highlighted how patients hospitalized for methamphetamine use had a significantly higher PD and parkinsonism risk. Alternately, another study showed that methamphetamine use increased PD risk by 3x.
• Despite the risk, incidences of PD in young adults are still low. Thus, Dr. Lappin and Dr. Darke believe that methamphetamine use could spur PD in those susceptible to the condition once they are older.
• Similar to patients with PD, brain scans of methamphetamine users highlighted substantia nigra alterations. Since this area is often where dopaminergic neuron death occurs, it accounts for similar symptom manifestations. Similarly, meth use has been linked to lower overall dopamine levels, which could spur PD onset.
• Smoking (tobacco/nicotine) conferred some protection against PD and parkinsonism.

Parkinson’s disease (PD)

Parkinson’s disease (PD) is a central nervous system disorder caused by dopamine-producing (dopaminergic) neuron death. Normally, dopamine plays a role in communication between the muscles and brain. When this communication is interrupted, patients experience progressively worsening movement issues. Doctors are not sure exactly what causes this neuron death. However, genetics, Lewy bodies, and environmental factors are all believed to play a part. Typically, PD occurs in five stages, the first being the mildest (with just light tremors) and the fifth being characterized by inability to stand or walk, hallucinations or delusions, and inability for patients to live independently. In many cases, PD onset occurs in older individuals (50+). Symptoms include:

• Muscle stiffness and rigidity
• Slowed movement
• Difficulty standing or walking
• A tremor in one or both hands
  • Note: The most common tremor is “pill-rolling,” in which patients rub their thumb and index finger back and forth.
• Changes in speech, such as slurring or stuttering
• Hallucinations or dementia
• Restless sleep or other sleep disturbances
• Loss of automatic movements (blinking, smiling)
• Incontinence
• Loss of smell
• Anxiety or apathy
• Impaired balance and posture