Because methamphetamine/amphetamine abuse damages dopamine-producing neurons in the brain, scientists have long suspected that it could be linked to an increased risk of Parkinson’s disease — a chronic condition in which the brain does not produce enough dopamine levels.
For the first time in epidemiological research, scientists at Toronto’s Centre for Addiction and Mental Health (CAMH) have confirmed in the journal Drug and Alcohol Dependence.
A significant study
Lead researcher Dr. Russell Callaghan — a specialist in social and epidemiological research at CAMH — and his team conducted a longitudinal cohort study following the progress of more than 280,000 patients from California where methamphetamine abuse is significantly more prevalent than most of the country. For the study, the researchers included individuals over the age of 30 who were admitted to statewide inpatient hospitals for methamphetamine/amphetamine abuse-related conditions, and tracked their health status for up to 16 years between 1990-2005. A total of 40,472 patients were identified as having methamphetamine/amphetamine abuse-related conditions based on their admissions or death records during the study’s time frame.
For comparison, the researchers matched the methamphetamine group with a representative population group consisting of 207,831 patients who were admitted for appendicitis, as well as a drug control group of patients admitted for cocaine-use disorders (35,335 patients). All of the patients were matched based on age, race, gender, date of admission, and number of admissions in order to make similar comparisons. Overall, the researchers sought to identity whether a history of methamphetamine/amphetamine abuse raises one’s risk for Parkinson’s disease, which is typically not diagnosed until later in life.
A significant risk
As a result of their analysis, the researchers found that the methamphetamine group was 76% more likely to develop Parkinson’s disease in later life than both the cocaine group and the appendicitis population group. Additionally, the cocaine group did not show an elevated risk of Parkinson’s disease when compared to just the appendicitis population group. Within a ten-year span, the researchers found that 21 in 10,000 individuals who abuse methamphetamine will develop Parkinson’s disease in middle or old age, yet only 10 in 10,000 individuals from the general population will end up developing Parkinson’s disease in later life.
Furthermore, the researchers caution that the methamphetamine abuse Parkinson’s disease link may be even higher than indicated by their data since many individuals who abuse methamphetamine often do not receive medical treatment due to lack of health insurance, and therefore were not accounted for by the study. The researchers also comment that prescribed use of amphetamines, such as that for attention deficit-hyperactivity disorder, is not associated with this increased risk since these prescriptions contain very low amounts of the substance compared to abused levels. The new study confirms similar findings discovered in previously conducted animal studies that identified an association between methamphetamine abuse and higher risk for Parkinson’s disease in mice.
Methamphetamine and amphetamine-like drugs make up the nation’s second leading type of illicitly abuse substances. Callaghan and his colleagues suggest their study is evidence of yet another long-term consequence of methamphetamine abuse, which clinicians should inform their patients with methamphetamine/amphetamine abuse-related conditions.