Persistent cognitive deficits attributed to substance abuse.

Abstract

This article exemplifies the major difficulties inherent in carrying out and interpreting human drug research. The information available about the long-term consequences of opiate use remains unclear. In fact, an overall summary of the persistent cognitive effects of long term drug use yields vague and tentative information (Table 2). An explanation of some of the methodologic constructs that have led to the majority of unclear conclusions may be helpful. 1. Baseline. One such important factor in providing an accurate assessment of the possible effects of long-term drug use is to have knowledge of the user's cognitive capacity before exposure to drugs. Such baseline information might be available from school records. 2. Repeated testing. Additionally, it is essential to have control groups and conditions, whereby the groups receive nearly identical testing on repeated occasions to assess whether findings remain consistent. 3. Observed Subjects. In choosing the subjects, polysubstance users are probably the most convenient group of individuals to study because of ease of availability, but very little about the effects of one specific drug class compared to another will be learned. Users do have decided drug preferences and ideally researchers should observe a user over a period of time with repeated urine testing to determine the pattern of use and as much information as possible about the dose. An adequate age range in both drug users and control subjects is helpful. 4. Age Range. One must control for the effects of aging, but if all of the subjects are very young, subtle cognitive deficits may be missed. If, however, subjects are too old, acute or chronic physical conditions that cause cognitive deficits may be impossible to differentiate from long-term drug effects. 5. Choice of Test. It is essential to match the appropriate test to the dependent variables being assessed. 6. Length of abstinence. For valid testing, subjects should be drug free confirmed by toxicology. The best studies have the longest periods of abstinence in a protected environment where drugs are not available. Recovery of function may occur weeks or months after last exposure to drugs. These standards are difficult to achieve, but many studies that have failed to attend to these issues have involved large expenditures of effort with little or no new knowledge as the outcome.