Can Childhood School Records Clarify Cognitive Differences in Methamphetamine Users?

Childhood academic records can help distinguish preexisting differences from later cognitive difficulties, but they cannot fully reconstruct a person’s original ability. A methamphetamine study used those records to improve a comparison that current education alone could not resolve.

A historical anchor before use

Dean and colleagues obtained childhood transcripts for 37 methamphetamine-dependent adults and 41 controls of similar educational level and estimated premorbid IQ. Participants completed cognitive testing and structural MRI. Investigators used control data to model expected adult cognitive performance from childhood academic performance and other predictors.

Both earlier and later differences appeared

The methamphetamine group had lower childhood grade-point averages before reported methamphetamine use. Its adult cognitive performance also fell below the model’s prediction, particularly in attention/concentration and memory. Thus a preexisting difference did not account for every observed adult difference.

Cortical thickness supplied an association

Within the methamphetamine group, memory deficits were related to lower overall cortical thickness. The study did not establish a significant cortical-thickness difference between the groups as a whole. A within-group relationship must not be converted into a universal anatomical signature of methamphetamine exposure.

Why this was not proof of an individual’s decline

The design was observational, and predicted ability was not a direct cognitive examination before drug use. Grades reflect educational opportunity, engagement and other influences. The model explained only part of performance variability, while other drug use and unidentified factors remained possible contributors. MRI measured anatomy rather than methamphetamine concentration; no forensic specimen cutoff was validated. The study strengthens the case for examining historical records while preserving uncertainty about the cause and magnitude of any individual’s cognitive change.

Related evidence

For a different perspective on interpreting stimulant evidence, see our analysis of education and cognitive-assessment limitations. Its study population and outcome should remain separate from the present findings.

Primary research

Cognitive deficit in methamphetamine users relative to childhood academic performance: link to cortical thickness. Original human research. doi:10.1038/s41386-018-0065-1.