Dominant and Non-Dominant Hands Showed Different Cannabis Pegboard Findings

A cannabis trial in spinal-cord-related neuropathic pain found a motor-performance difference for the non-dominant hand without the same dominant-hand result. Combining the hands into a general statement would lose the measured pattern.

The review separated the two tests

Eadie and colleagues describe Grooved Pegboard testing of dominant and non-dominant hands in a vaporized-cannabis trial. The task assesses manual dexterity and fine motor control. These were clinical human participants with disease or injury affecting the spinal cord.

The affected comparison was specific

The review reports no significant dose-effect differences on the dominant-hand test. The higher-THC condition performed worse than placebo on the non-dominant-hand measure after the second dosing session, with the difference no longer observed at a later assessment. The result should preserve hand, dose and time rather than becoming uniform motor impairment.

A selective null is not proof of full functional recovery

The dominant-hand result does not validate every activity requiring coordination, and the non-dominant finding does not prove that both hands were equally affected. Physical disability can also complicate task completion in this population. The appropriate inference is about the actual comparison, not a universal ability or inability to operate a vehicle. A useful opinion identifies the limb and task relevant to the disputed function before borrowing a general motor label.

Related analysis: the review’s broader findings and limitations.

Research cited

This analysis draws on the supplied review: Eadie and colleagues (2021). Duration of Neurocognitive Impairment With Medical Cannabis Use: A Scoping Review. Frontiers in Psychiatry.

Study discussed in that review: DOI 10.1016/j.jpain.2016.05.010.