Methamphetamine and Attention: Two Studies Showing Measured Performance Improvements
Claims about methamphetamine and performance should identify an actual measured function. Two controlled human studies found improvements in divided attention after methamphetamine administration. Their results deserve precise treatment when scientific evidence is discussed.
Hart: faster responses and improved tracking
In a 2008 study, Hart and colleagues tested 11 experienced methamphetamine users under placebo and intranasal methamphetamine conditions. The active doses improved maximum tracking speed and reduced response latency on a divided-attention task. Intermediate doses also improved the number of attempts and correct responses on digit-symbol substitution. Other tested performance outcomes did not significantly change. [1]
The distinction between the tasks matters. Tracking a moving target while responding to another stimulus is one operational measure of attention. Digit-symbol substitution measures a different performance demand. Neither should be described simply as proof that the drug improves every cognitive function.
Kirkpatrick: improvement in a direct comparison
A 2012 study by Kirkpatrick and colleagues compared methamphetamine with dextroamphetamine and placebo in 13 male recreational methamphetamine users. Both stimulants increased maximum tracking speed. The smaller doses reduced response latency. No other significant acute performance effects were found, and the researchers reported no significant residual performance effects. [2]
This study belongs in a methamphetamine performance discussion because methamphetamine was directly administered. It is not merely a study of another stimulant used as a substitute for methamphetamine evidence.
Applying the findings accurately
These experiments undermine an unqualified statement that methamphetamine must reduce performance on every attention task. They support a narrower proposition: measurable improvements occurred on particular tasks in particular study populations.
The forensic question is whether that experimental result bears on the function being discussed in an individual matter. A laboratory divided-attention result alone cannot resolve the person’s driving performance, judgment, or functioning at the relevant time. A sound analysis states the affirmative finding, identifies its limits, and then evaluates the actual record.
For related case-specific questions, see Methamphetamine Driving Cases: Records and Scientific Questions.
References
- Hart CL, et al. (2008). Acute Physiological and Behavioral Effects of Intranasal Methamphetamine in Humans. DOI: 10.1038/sj.npp.1301578.
- Kirkpatrick MG, et al. (2012). Comparison of intranasal methamphetamine and d-amphetamine self-administration by humans. DOI: 10.1111/j.1360-0443.2011.03706.x.
