People who abuse crystal meth and similar drugs are far more likely to develop Parkinson's disease later in life, a new study has found.
Researchers have long suspected a link between meth use and Parkinson's, a brain disorder that causes tremors and difficulty moving.
That's because Parkinson's is caused by the brain's inability to produce the chemical dopamine, and previous studies have shown that methamphetamine use damages dopamine-producing areas of the brain in animal test subjects.
But this is the first study to examine the connections between meth and Parkinson's in humans, and the results show an extreme connection.
Researchers examined some 300,000 hospital records from California, a state known for its high rates of meth use, and found patients admitted for methamphetamine- or amphetamine-use disorders had a 76% higher risk of developing Parkinson's than other patients.
"This study provides evidence of this association for the first time, even though it has been suspected for 30 years," said lead researcher Dr. Russell Callaghan, a scientist with the Centre for Addiction and Mental Health (CAMH) in Toronto.
The findings are significant because meth and similar stimulants are the second-most commonly used illicit drugs in the world, he said.
"The current study will help us anticipate the full long-term medical consequences of such problematic drug use," he said.
The researchers said those taking the drugs legitimately are likely safe from the risk of developing Parkinson's.
"It is important for the public to know that our findings do not apply to patients who take amphetamines for medical purposes, such as attention deficit hyperactivity disorder, since these patients use much lower doses of amphetamines than those taken by patients in our study," said Dr. Stephen Kish, a CAMH scientist and co-author of the study.