Contemporary Drug Problems
September 1, 2019
Hannes Kettner, Natasha L. Mason, Kim P. C. Kuypers
50 citations
Novel psychoactive substances (NPS) are compounds designed to mimic the effects of existing recreational drugs (classical psychoactive substances [CPS]), while eluding established legal frameworks. Little is known about their effects and potential harms, rendering the increasing number of NPS a challenge to policy makers and researchers alike. Quantitative studies on the motives underlying NPS...
Journal of Psychopharmacology
July 14, 2019
Livia Ng, Luca Pani, Anaïs Soula et al.
Background: In the past few years, the issue of ‘microdosing’ psychedelics has been openly discussed in the public arena where claims have been made about their positive effect on mood state and cognitive processes such as concentration. However, there are very few scientific studies that have specifically addressed this issue, and there is no agreed scientific consensus on what microdosing is....
The International Journal of Neuropsychopharmacology
May 30, 2019
Nadia R. P. W. Hutten, Natasha L. Mason, Patrick C. Dolder et al.
132 citations
Abstract Background Microdosing with psychedelics has gained considerable media attention where it is portrayed as a performance enhancer, especially popular on the work floor. While reports are in general positive, scientific evidence about potential negative effects is lacking aside from the prevalence and motives for use. The present study addressed this gap by surveying psychedelic users...
Drug Testing and Analysis
March 26, 2019
Stefan W. Toennes, David J. Schneider, Werner Pogoda et al.
9 citations
INTRODUCTION: Each year, synthetic drugs occur in high numbers on the illicit drug market. But data on their pharmacology and toxicology are scarce. Therefore, a controlled study was performed to evaluate pharmacokinetic parameters of 4-fluoroamphetamine (4-FA) in humans and to compare it with effects. METHODS: Twelve subjects ingested 100 mg and five subjects also received 150 mg 4-FA in a...
Cannabis and Cannabinoid Research
February 27, 2019
Eef L. Theunissen, Nadia R. P. W. Hutten, Natasha L. Mason et al.
22 citations
Abstract Introduction: Synthetic cannabinoid mixtures have been easily accessible for years, leading to the belief that these products were natural and harmless, which contributed to their popularity. Nevertheless, there are many reports of users ending up in hospital due to severe side effects such as tachycardia, aggression, and psychosis. Controlled studies on the effects of synthetic...
Journal of Psychoactive Drugs
February 26, 2019
Natasha L. Mason, Elisabeth Mischler, Malin V. Uthaug et al.
176 citations
Creative thinking and empathy are crucial for everyday interactions and subjective well-being. This is emphasized by studies showing a reduction in these skills in populations where social interaction and subjective well-being are significantly compromised (e.g., depression). Anecdotal reports and recent studies suggest that a single administration of psilocybin can enhance such processes and...
Journal of Psychoactive Drugs
January 24, 2019
Kim P. C. Kuypers, E. B. de Sousa Fernandes Perna, Eef L. Theunissen et al.
13 citations
The phenethylamine 4-fluoroamphetamine (4-FA) is a so-called novel psychoactive substance with a chemical structure resembling that of amphetamine and MDMA. Since 4-FA users report their subjective experience ranges between the effects induced by amphetamine and MDMA, and it is known that both substances can produce an altered state of consciousness, this study tests whether 4-FA induces a...
Human Psychopharmacology Clinical and Experimental
October 25, 2018
Patrick C. Dolder, Elizabeth B. de Sousa Fernandes Perna, Natasha L. Mason et al.
6 citations
OBJECTIVES: 4-Fluoroamphetamine (4-FA) is a novel psychoactive substance with a pharmacological profile and reported subjective effects (e.g., empathy) intermediate between 3,4-methylenedioxymethamphetamine (MDMA) and amphetamine. Studies have shown that MDMA and amphetamine increase emotional empathy without affecting cognitive empathy; MDMA simultaneously leads to elevated levels of oxytocin,...
Psychopharmacology
August 13, 2018
Malin V. Uthaug, Kim van Oorsouw, Kim P. C. Kuypers et al.
213 citations
RATIONALE: Ayahuasca is a psychotropic plant tea from South America used for religious purposes by indigenous people of the Amazon. Increasing evidence indicates that ayahuasca may have therapeutic potential in the treatment of mental health disorders and can enhance mindfulness-related capacities. Most research so far has focused on acute and sub-acute effects of ayahuasca on mental...
Frontiers in Pharmacology
July 6, 2018
Elizabeth B. de Sousa Fernandes Perna, Eef L. Theunissen, Patrick C. Dolder et al.
18 citations
Availability of novel psychoactive substances (NPS) exponentially increased over the last years. Risk evaluations of NPS are hampered by the lack of pharmacological studies in humans on health parameters. The aim of the present study was Tto evaluate safety and neurocognitive function of healthy volunteers (N=12) who received single doses of 100 and 150 mg 4-fluoroamphetamine (4-FA), a...
Journal of Psychedelic Studies
June 1, 2018
Natasha L. Mason, Kim P. C. Kuypers
27 citations
A substantial number of people worldwide suffer from mental health problems during their lifetime. First-line treatments are not effective for everybody. Recent studies suggest that psychedelic drugs have high therapeutic potential for a variety of mental disorders. This survey study aimed to assess the tendency of psychedelic users to self-medicate with psychedelics and to compare the...
Psychopharmacology
May 31, 2018
Kim P. C. Kuypers, E. B. de Sousa Fernandes Perna, Patrick C. Dolder et al.
14 citations
BACKGROUND: New psychoactive substances (NPS) are chemical analogues designed to mimic the effects of various classic recreational drugs of abuse including MDMA, LSD, and cannabis. NPS use is associated with concern about the acute and longer-term effects particular substances might have, with abuse and addiction as potential consequences. Impulsivity and sensitivity to the rewarding effects of...
Scientific Reports
January 12, 2018
Kim P. C. Kuypers, Rafael de la Torre, Magı́ Farré et al.
12 citations
Abstract MDMA exerts its main effects via the serotonergic system and the serotonin transporter. The gene coding for this transporter determines the expression rate of the transporter. Previously it was shown that healthy individuals with the short allelic variant (‘ s -group’) of the 5-HTTLPR-polymorphism displayed more anxiety and negative mood, and had a lower transcriptional efficiency...
British Journal of Pharmacology
November 22, 2017
Eef L. Theunissen, Nadia R. P. W. Hutten, Natasha L. Mason et al.
38 citations
BACKGROUND AND PURPOSE: Synthetic cannabinoids (often sold as Spice or K2) have become a very popular alternative to cannabis due to their easy access and portrayed safety. Controlled studies on the behavioural effects of synthetic cannabinoids are currently lacking, which hampers risk assessments of these compounds. EXPERIMENTAL APPROACH: This is a first attempt to assess the influence of a...
Psychopharmacology
November 16, 2017
Eline Haijen, Magı́ Farré, Rafael de la Torre et al.
9 citations
Preclinical data have suggested involvement of the endocannabinoid (eCB) system in MDMA-induced memory impairment. Clinical research has shown that blockade of the 5-HT 2 receptor nulls memory impairment during MDMA intoxication. Interestingly, studies have demonstrated that the eCB and the 5-HT system interact. It was hypothesized that MDMA would cause an increase in eCB concentrations...
Psychopharmacology
July 22, 2017
Kim P. C. Kuypers, Rafael de la Torre, Magı́ Farré et al.
24 citations
MDMA has been shown to induce feelings of sociability, a positive emotional bias and enhanced empathy. While previous research has used only visual emotional stimuli, communication entails more than that single dimension and it is known that auditory information is also crucial in this process. In addition, it is, however, unclear what the neurobiological mechanism underlying these MDMA effects...
Frontiers in Pharmacology
July 11, 2017
Drew J. Puxty, Johannes G. Ramaekers, Rafael de la Torre et al.
33 citations
Previous research has shown that a single dose of MDMA induce a dissociative state, by elevating feelings of depersonalization and derealization. Typically, it is assumed that action on the 5-HT2A receptor is the mechanism underlying these psychedelic experiences. In addition, other studies have shown associations between dissociative states and biological parameters (heart rate, cortisol),...
Journal of Psychopharmacology
April 3, 2017
Kim P. C. Kuypers, Patrick C. Dolder, Johannes G. Ramaekers et al.
88 citations
Previous placebo-controlled experimental studies have shown that a single dose of MDMA can increase emotional empathy in the multifaceted empathy test (MET) without affecting cognitive empathy. Although sufficiently powered to detect main effects of MDMA, these studies were generally underpowered to also validly assess contributions of additional parameters, such as sex, drug use history, trait...
Journal of Psychopharmacology
August 25, 2016
EB de Sousa Fernandes Perna, Esther Papaseit, Clara Pérez‐mañá et al.
26 citations
Recreational use of mephedrone, alone and in combination with alcohol, has increased over the past years. Pharmacological properties of mephedrone share similarities with methylenedioxymethamphetamine (MDMA), but its effect on neurocognitive function has not been well established in humans. The present study assessed the effect of mephedrone alone and after co-administration with alcohol on...
Psychopharmacology
July 19, 2016
Kim P. C. Kuypers, Jordi Riba, Mario de la Fuente Revenga et al.
204 citations
INTRODUCTION: Ayahuasca is a South American psychotropic plant tea traditionally used in Amazonian shamanism. The tea contains the psychedelic 5-HT2A receptor agonist N,N-dimethyltryptamine (DMT), plus β-carboline alkaloids with monoamine oxidase-inhibiting properties. Increasing evidence from anecdotal reports and open-label studies indicates that ayahuasca may have therapeutic effects in...
Scientific Reports
May 26, 2016
Johannes G. Ramaekers, J. H. van Wel, Desirée Spronk et al.
81 citations
Cannabis use history as predictor of neurocognitive response to cannabis intoxication remains subject to scientific and policy debates. The present study assessed the influence of cannabis on neurocognition in cannabis users whose cannabis use history ranged from infrequent to daily use. Drug users (N = 122) received acute doses of cannabis (300 μg/kg THC), cocaine HCl (300 mg) and placebo....
PLoS One
February 23, 2016
Kim P. C. Kuypers, Eef L. Theunissen, Janelle H. P. van Wel et al.
23 citations
BACKGROUND: Ecstasy use has been associated with short-term and long-term memory deficits on a standard Word Learning Task (WLT). The clinical relevance of this has been debated and is currently unknown. The present study aimed at evaluating the clinical relevance of verbal memory impairment in Ecstasy users. To that end, clinical memory impairment was defined as decrement in memory performance...
Brain Imaging and Behavior
December 14, 2015
Johannes G. Ramaekers, J. H. van Wel, Desirée Spronk et al.
61 citations
The dopamine β-hydroxylase (DβH) enzyme transforms dopamine into noradrenaline. We hypothesized that individuals with low activity DBH genotypes (rs1611115 CT/TT) are more sensitive to the influence of cannabis and cocaine on cognitive impulse control and functional connectivity in the limbic 'reward' circuit because they experience a drug induced hyperdopaminergic state compared to individuals...
Journal of Psychopharmacology
January 8, 2015
JHP van Wel, DB Spronk, Kim P. C. Kuypers et al.
23 citations
Trait impulsivity has been linked to addiction in humans. It has been suggested that drug users with high trait impulsivity levels are more sensitive to subjective drug intoxication. This study assessed whether subjective response to drugs differs between drug users with normal or high levels of trait impulsivity. Regular drug users (N = 122) received doses of cocaine HCl, cannabis, and placebo...
PLoS One
June 27, 2014
Kim P. C. Kuypers, Rafael de la Torre, Magı́ Farré et al.
88 citations
The present study aimed at investigating the effect of MDMA on measures of empathy and social interaction, and the roles of oxytocin and the 5-HT1A receptor in these effects. The design was placebo-controlled within-subject with 4 treatment conditions: MDMA (75 mg), with or without pindolol (20 mg), oxytocin nasal spray (40 IU+16 IU) or placebo. Participants were 20 healthy poly-drug MDMA...