Impaired motor cortical plasticity associated with cannabis use disorder in young adults

Maladaptive cortical plasticity has been described in individuals with heroin and methamphetamine addiction and may mediate other substance abuse disorders. It is unknown whether cannabis dependence in humans alters the capacity for induction of cortical plasticity. The aim of this study was to non‐invasively investigate cortical plasticity with transcranial magnetic stimulation in young adults who meet DSM‐5 criteria for cannabis use disorder (CUD). Thirty men (ages 20– 30) who used cannabis daily over the previous 6 months (15 diagnosed of CUD) and 15 demographically matched non‐users were enrolled in this study. All participants underwent two sessions of theta burst stimulation (TBS) in which either continuous TBS (cTBS; 600 pulses, 80% active motor threshold) or intermittent TBS (iTBS; 2‐s train of cTBS repeated every 10 s for a total of 190 s, 600 pulses) was applied over the primary motor cortex. The effects of these protocols were assessed by analysing the contralateral motor evoked potentials (MEPs). The relationships between cortical plasticity and problematic cannabis use, degree of dependence, and nicotine addiction were also investigated. Significant MEP inhibition after cTBS was observed in both cannabis users without CUD and non‐users, while this inhibition was not seen in cannabis users with CUD. Strikingly, less motor cortical plasticity was observed in subjects with severe problematic cannabis use. No significant differences between users and non‐users were found in the iTBS‐induced cortical plasticity measures. Our study provides the first evidence of maladaptive cortical plasticity associated with cannabis use disorder and problematic cannabis use in humans.
This work was supported by the Instituto de Salud Carlos III‐Fondo Europeo de Desarrollo Regional (ISCIII‐FEDER) (PI14/01823, PI16/01575), the Consejería de Economía, Innovación, Ciencia y Empleo de la Junta de Andalucía (CVI‐02526, CTS‐7685), the Consejería de Salud y Bienestar Social de la Junta de Andalucía (PI‐0437‐2012, PI‐0471/2013), the Fundación Progreso y Salud (FPS 2014 PI‐0055‐2014), the Sociedad Andaluza de Neurología, the Fundación Alicia Koplowitz and the Fundación Mutua Madrileña. J.F.M.‐R. was supported by the “Sara Borrell” Programme from the Instituto de Salud Carlos III and the VI PPIT‐US from the University of Seville; P.A.d.T. was supported by the FPU programme of the Ministry of Education, Culture and Sport of Spain; and M.R.‐V. was supported by Grant BAE 09/90088.