No abstract

Regulations targeting precursors used by large-scale producers reduced admissions substantially during the study period. However, the regulation of precursors used primarily by small-scale producers had little, if any, effect.

Study limitations include difficulty in confirming schizophrenia diagnoses independent of drug intoxication and the possibility of undetected schizophrenia predating drug exposure. The study's findings suggest that individuals with methamphetamine-related disorders have a higher risk of schizophrenia than those with other drug use disorders, with the exception of cannabis use disorders. The elevated risk in methamphetamine users may be explained by shared etiological mechanisms involved in the development of schizophrenia.

Precursor regulations targeting large-scale producers impacted methamphetamine arrests, a criminal justice problem, much as they impacted the public health problem of methamphetamine hospital admissions. Ongoing research is needed to determine whether these problems eventually fully rebound from the last regulation.

Because methamphetamine exposure to experimental animals can damage brain dopamine neurones, we examined whether hospital patients diagnosed with methamphetamine-related disorders might have greater risk of subsequent admission with a Parkinson's disease diagnosis. This was a population-based cohort study using all statewide inpatient hospital discharge records from July 1, 1990, through June 30, 2000, in California, USA, in which subjects aged at least 50 years were followed for up to 10 years. Individuals with reported methamphetamine-related conditions (n = 1,863; ICD-9 codes 304.4, 305.7, 969.7, and E854.2) were matched on demographic variables and follow-up time with those with primary appendicitis conditions (n = 9,315). The appendicitis group had a Parkinson's disease incidence rate no different than the rate found among members of a large health maintenance organization in California. Cox regression procedures were used to estimate group differences in the rates of receiving a subsequent inpatient diagnosis of Parkinson's disease (ICD-9 332.0). The methamphetamine group showed increased risk of a subsequent admission with Parkinson's disease compared with that of the matched appendicitis group (adjusted hazard ratio = 2.65, 95% CI, 1.17-5.98, P= 0.019). Study limitations include a population limited to hospital admissions, an uncertainty regarding diagnostic validity of the ICD-9 code 332.0 (Parkinson's disease), and a small number of incident cases with suspected Parkinson's disease. We strongly emphasize the preliminary nature of the findings. Nevertheless, these data, requiring replication, provide some evidence that methamphetamine users might be at greater than normal risk for developing Parkinson's disease.