Heightened excitability and impaired Inhibition in methamphetamine users: a pilot study of neurophysiological correlates of psychological symptoms.

BACKGROUND

In this study, we investigated transcranial magnetic stimulation (TMS)-derived markers of excitability and inhibition in methamphetamine (METH) use disorder.

METHODS

Sixteen methamphetamine users and 20 matched controls underwent psychological assessments, revised form of Symptom Checklist-90-Revised, cognitive assessment, anxiety and depression scales and TMS measures, including resting and active motor thresholds (RMT and AMT), motor evoked potential amplitude (MEP-A), cortical silent period (CSP), and short-interval intracortical inhibition (SICI).

RESULTS

METH users reported higher anxiety, depression, and somatization (p < 0.001), while cognition remained preserved. They exhibited reduced RMT and AMT (p < 0.001), indicating increased excitability, with no significant differences in MEP-A (p = 0.083). CSP onset latency was prolonged at 150% RMT (p = 0.042), suggesting impaired inhibition. Excitability thresholds correlated negatively with methamphetamine dose, while addiction duration was linked to CSP changes and obsessive-compulsive symptoms. Lower thresholds also correlated with greater interpersonal sensitivity and addiction severity.

CONCLUSION

Increased cortical excitability and decreased inhibitory control are linked to METH usage, and these factors may be underlying psychiatric symptoms. TMS-derived indices show potential as biomarkers for neurophysiological monitoring and targeted interventions in methamphetamine use disorder.