Does a Parkinsonian-Like Test Pattern Diagnose Parkinson Disease After Methamphetamine Use?

No. A Parkinsonian-like pattern on a cognitive task is not a diagnosis of Parkinson disease. A 2026 study used that comparison to describe selected test differences in recently abstinent methamphetamine users, without establishing their future disease risk.

The task and the sample

Dumitrescu and colleagues compared 49 participants with methamphetamine use disorder from a residential treatment program with 30 controls. The methamphetamine group included 26 men and 23 women. Trail Making performance supplied measures of completion time and errors relevant to cognitive flexibility and processing demands.

Which associations were reported

Both sexes in the methamphetamine group showed Trail Making deficits relative to controls. Reported age at first use, duration and amount used did not explain performance in the reported analyses. Intravenous use was associated with more errors in women, but not men. This subgroup finding should not be converted into proof that injecting causes Parkinson disease in women.

What was not established

The study did not demonstrate clinical equivalence between methamphetamine use disorder and Parkinson disease. It did not prospectively measure later Parkinson diagnoses. A test sensitive to frontostriatal difficulty can be affected by multiple conditions and is not a disease-specific biological marker.

Exposure timing was incompletely measured

The paper states that systematic toxicology data and precise time since last methamphetamine use were unavailable. Routine monitoring in a treatment setting is not a controlled drug washout experiment. There was no validated whole-blood or urine concentration threshold for this test pattern. Observational selection, subgroup sizes and incomplete exposure timing constrain causal claims. The useful conclusion concerns measured cognitive performance, not a neurological diagnosis or a prediction about an individual driver’s impairment.

Related evidence

For a different perspective on interpreting stimulant evidence, see our analysis of the Swedish amphetamine concentration study. Its study population and outcome should remain separate from the present findings.

Primary research

Trail Making Test performance in early abstinence from methamphetamine: human evidence for a drug-associated Parkinsonian-like phenotype. Original human research. doi:10.3389/fpsyt.2026.1773668.