Canadian scientists say there's a link between the abuse of methamphetamines and the development of Parkinson's disease.
Researchers at the Centre for Addiction and Mental Health in Toronto used medical records for more than 40,000 people in California who had been hospitalized for abusing meth- or amphetamine-like stimulants from 1990 to 2005.
They were compared to records for more than 200,000 people admitted for appendicitis, and more than 35,000 diagnosed with cocaine use disorders.
A diagnosis of Parkinson's was identified from hospital records or death certificates.
76 per cent higher risk
The study found that the methamphetamine group had a 76 per cent higher risk of developing Parkinson's disease.
Dr. Stephen Kish, a co-author of the paper, says it's important to note that the findings don't apply to patients like those with ADHD who take amphetamines for medical purposes, since they use much lower doses.
Researchers have long suspected that abuse of these drugs could predispose users to develop Parkinson's disease, which is a dopamine deficiency neurological disorder.
That's because meth and other amphetamine-type stimulants, which are believed to be the second most widely used class of illicit drugs in the world, can damage dopaminergic neurons.
The findings are published in the journal Drug and Alcohol Dependence.