Skip to content

Robbert J. Verkes

5 papers in the library · 408 citations · publishing 2008-2016

Papers

Increased oxytocin concentrations and prosocial feelings in humans after ecstasy (3,4-methylenedioxymethamphetamine) administration

Social Neuroscience June 25, 2009 Glenn Dumont, Fred C.g.j. Sweep, R. van der Steen et al. 238 citations

MDMA (ecstasy) causes a strong increase in blood oxytocin levels and enhances feelings of prosociality in healthy people. The changes in prosocial feelings are more closely tied to changes in oxytocin than to changes in MDMA concentration in the blood. This suggests that oxytocin release may be a key mechanism behind the drug's characteristic social effects.

Cannabis and tolerance: acute drug impairment as a function of cannabis use history

Scientific Reports May 26, 2016 Johannes G. Ramaekers, J. H. van Wel, Desirée Spronk et al. 81 citations

Acute cannabis intoxication impairs executive function, impulse control, attention, and psychomotor function, and increases subjective intoxication, regardless of how frequently a person uses cannabis. In a study of 122 drug users with cannabis use histories ranging from infrequent to daily, cannabis (300 μg/kg THC) produced these deficits compared to placebo, while cocaine (300 mg) improved psychomotor function and attention but impaired impulse control. The absence of tolerance to cannabis's neurocognitive effects suggests that frequent use and intoxication can interfere with performance in daily environments such as school, work, or traffic.

Acute neuropsychological effects of MDMA and ethanol (co-)administration in healthy volunteers

Psychopharmacology February 28, 2008 Glenn Dumont, E. Wezenberg, M. M. G. J. Valkenberg et al. 50 citations

Taking MDMA and ethanol together does not worsen the effects of either drug alone. While the impairment caused by each drug condition was relatively moderate, all drug conditions significantly impaired cognitive function.

Single doses of THC and cocaine decrease proficiency of impulse control in heavy cannabis users

British Journal of Pharmacology October 11, 2013 Janelle H. P. van Wel, Kim P. C. Kuypers, Eef L. Theunissen et al. 38 citations

Heavy cannabis users show broad impairments in neuropsychological function during THC intoxication, including reduced psychomotor performance and more errors on impulsivity tasks. These impairments appear less severe in psychomotor tasks than those previously seen in occasional users, suggesting some tolerance. Cocaine temporarily improves psychomotor function and speeds reaction times but increases errors, indicating a trade-off between stimulation and impulse control. The decline in impulse control may increase the risk of repeated drug use and addiction.

Treatment of heroin dependence with ibogaine

European Psychiatry March 1, 2016 Arnt Schellekens, Toon van Oosteren, Thomas Knuijver et al. 1 citation

Ibogaine, a hallucinogen, reduces drug self-administration in animals, especially within the first 24 hours, but causes motor impairment and cerebral cell loss. In a meta-analysis of 27 animal studies, ibogaine did not affect conditioned place preference. Human data from 15 opiate-dependent patients treated with 10 mg/kg ibogaine are still being collected; initial observations show strong QTc prolongation and ataxia, with relatively mild opiate withdrawal symptoms. Ibogaine may reduce opiate withdrawal but carries risks of transient cardiac and cerebellar toxicity, warranting further systematic studies on its safety and efficacy for treating opiate dependence.