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Psychedelic drugs, magical thinking and psychosis.
Abstract
After completing an undergraduate degree in Psychology in 2003, Robin studied psychoanalysis at Masters level, receiving his MA in 2004. In 2005, Robin began a four year PhD in Psychopharmacology at the University of Bristol. Working for Professor David Nutt and Dr Sue Wilson, Robin's thesis focused on sleep and serotonin function in ecstasy users. Robin conducted a clinical study involving sleep electroencephalography (EEG) and tryptophan depletion. In 2009, working closely with the Beckley Foundation, he successfully coordinated the first clinical study of psilocybin in the UK and the first clinical study of a classic psychedelic drug in the UK for over 40 years. Also in 2009, Robin moved to Imperial College London to continue his work under the supervision of Professor David Nutt. With the collaboration of Professor Richard Wise at Cardiff University, Robin has since coordinated the first resting state fMRI investigation of a classic psychedelic drug and the first fMRI and PET investigations of psilocybin and MDMA. Robin is first author on a number of publications in peer-reviewed scientific journals including review articles with eminent neuroscientists Professor's Helen Mayberg and Karl Friston. He has presented his data at several international conferences and has appeared on BBC News.
Psychedelic ('psyche'=soul/mind and 'delos'=to make visible or clear) drugs have been used for centuries in mystical ceremonies. In the 1950/60s they were used widely in psychotherapy, under the premise that they lower psychological defences and facilitate psychological insight. Since the 1950s, the psychedelic state has been considered a model of psychosis. Today, all of these properties of psychedelics are researched: a single high-dose of psilocybin (magic mushrooms) has been found to produce profound, personality-changing spiritual-type experiences in healthy participants1, 2, psilocybin has been found to be effective in psychotherapy for end-of-life anxiety3 and the pharmacological pathways through which psychedelic effects are elicited (i.e. stimulation of the serotonin 2A receptor) continue to be linked with psychosis4. These variegated properties do not seem entirely consistent with one another - e.g. how can the same drug be both psychotomimetic and therapeutically useful? This presentation will attempt to resolve this apparent paradox. Evidence will be cited to support the hypothesis that the prodromal phase of first-episode psychosis, spontaneously occurring spiritual experiences and the psychedelic drug state rest on the same neurobiological state - hereafter referred to as the primitive state. This state is described psychologically as evolutionarily regressive, i.e. it is a state the mind and brain falls back to under certain conditions. This evolutionarily primitive state is characterised by magical thinking: i.e. fallacious thinking in which reality-testing is disavowed and thoughts are easily biased by wishes and anxieties. In the spiritual experience it is wishful fantasies that predominate (although not entirely) and in psychosis, it is paranoid thinking. In the psychedelic state, both wishful and paranoid thinking are common and the valence of the experience is highly sensitive to the environment in which it unfolds. That this state is so sensitive to environmental perturbation has important implications for both psychotherapy with psychedelics and treatment approaches for patients exhibiting signs of psychosis-risk - as it emphasises the importance of shepherding the experience in a positive direction. Underneath its sensitivity to suggestion however, is a more fundamental property of the primitive state: that the perception of difference or separateness breaks down. Evidence from functional brain imaging of a decrease in the orthogonality of different brain states in psychosis, the psychedelic-state and the meditative state is presented - and used to support the hypothesis that there is a breakdown of 'multiplicity' in the primitive state which lies at the base of descriptions of 'union' or 'oneness'5.
... However, in cases of too much or a chronic underactive filter, the leaky filter can allow "too much 'Mind at Large' to enter conscious awareness, potentially resulting in perceptual instability, cognitive confusion, or hallucination" (Swanson, 2018, p. 8). More recently, Robin Carhart-Harris has proposed a model of "cognitive entropy," suggesting that both early experiences of psychosis and psychedelic experiences occur in the same "primitive state" characterized by magical thinking, cognitive looseness, imagination, and flexible, creative thinking (Carhart-Harris, 2013;Carhart-Harris et al., 2014, 2016. As with the leaky filter model, the paradox is resolved; such entropy can either lead to symptoms of psychosis, as new meanings and perceptions come rapidly into view, or allow for productive therapeutic engagement outside of one's usual way of thinking (Swanson, 2018). ...
... In particular, research into potential shared mechanisms, notably through the activation of serotonin 5-HT 2A receptors, seen in both types of experience, is ongoing (Geyer & Vollenweider, 2008;Nichols, 2004). Relatedly, there has been interest in the question of whether anti-psychotics tend to block psychedelics experiences, 7 similarities and differences between drug-induced and endogenous hallucinations (Leptourgos et al., 2020), and potential links between early psychotic and psychedelic experiences (Carhart-Harris, 2013;Hartogsohn, 2020;Langlitz, 2013). Psychedelics are also regularly used in animal research to model symptoms of psychosis, although several other options are available as well 8 (Halberstadt & Geyer, 2013). ...
Experiences of psychedelics and psychosis were deeply entangled in scientific practices in the mid-20th century, from uses of psychedelic drugs that could model psychosis, to detailed phenomenological comparisons of endogenous and drug-induced madness. After the moral panic of the 1960s shut down psychedelic research, however, these two phenomena became disentangled. In the decades following, the science of psychosis transformed, shedding the language of psychoanalysis, and adopting the new scientific veneer of psychiatry. Today, as psychedelic science re-emerges, the research programs surrounding psychosis and psychedelics now stand in stark contrast. Here, I look closely at how these research programs respond to questions related to what is worth measuring, what is worth investigating, and how we ought to respond to these experiences. This comparison reveals radically different assumptions and values that guide each research paradigm and shape clinical practice. While psychedelic research often includes scales that seek to capture experiences of mysticism, meaningfulness, and ego dissolution, research related to psychosis focuses on the measurement of pathological symptoms and functioning. Research into psychosis primarily seeks universal and reductionist causal explanations and interventions, while psychedelic research embraces the importance of set and setting in shaping unique experiences. Responses to psychedelic crisis involve warmth, compassion, and support, while responses to psychotic experiences often involve restraint, seclusion, and weapons. I argue that these differences contain important lessons for psychiatry. However, as psychedelic research struggles to meet regulatory requirements and fit within the paradigm of evidence-based medicine, these differences may quickly dissolve.
... The mechanisms by which psychedelics can yield beneficial outcomes for psychiatric subjects are still under investigation. Certainly, these drugs produce a profound psychological effect in which perceptions are enhanced in ways that augment the sense of the meaningfulness of the therapeutic environment ( Hartogsohn, 2018 ;Kaelen et al., 2015 ;Carhart-Harris, 2013 ). Some have noted that psychedelics amplify creative or divergent thinking ( Hartogsohn, 2017 ;Hartogshon, 2018 ;Kaelen et al., 2015 ), which may help to promote novel selfassessment and insight and heighten one's sense of connectedness to the world. ...
... Some have noted that psychedelics amplify creative or divergent thinking ( Hartogsohn, 2017 ;Hartogshon, 2018 ;Kaelen et al., 2015 ), which may help to promote novel selfassessment and insight and heighten one's sense of connectedness to the world. Others have noted the psychedelics can bring about a change in brain state that is evolutionarily regressive ( Carhart-Harris, 2013 ) and by doing so, leaves psychological wellbeing vulnerable to suggestion. For these reasons, the therapeutic setting deserves critical attention in that it can have a powerful effect on the benefits of treatment. ...
Recent interest has emerged regarding the use of several short-acting pharmacotherapies that may be explicitly delivered in the context of psychotherapy for anxiety, mood and substance-dependence disorders. Our objective in this narrative review is to highlight the potential of medically-assisted psychotherapy by outlining the current state of research on some of these drugs, including D-cycloserine, propranolol, and psychedelics, and describing the basic science that supports their use. The neurobiological learning and memory theories that correspond to the manner in which these drugs function are also discussed. Although the efficacy of the medically-assisted psychotherapies reviewed is still under investigation, we propose that these novel treatment approaches may be preferred over traditional psychopharmacological treatments for many reasons, including the presence of fewer chronic side effects, as well as a lesser toxicity and abuse potential. Furthermore, some clinical research suggests that adjunctive pharmacotherapies may help to reinforce the psychotherapeutic alliance and may ultimately yield better long-term treatment outcomes for this reason, alone. If at least some of the adjunctive pharmacotherapies outlined in this review are found to be clinically efficacious and safe, mental health patients will benefit from having more treatment options available to them in the future.
... One study found that higher levels of pre-treatment paranoia and interpersonal sensitivity were associated with great patient discomfort with audio and video recording of psychotherapy sessions (13). Further, paranoid thinking is a common feature of psychedelic mental states, and is highly sensitive to changes in the environment and context in which the psychedelic experience takes place (15). Thus, situated awareness of a camera could exacerbate patient discomfort and shape the therapeutic context in ways that alter psychedelic effects related to paranoid thinking. ...
In light of high-profile cases of sexual assault and other unethical conduct by therapists, recent clinical research involving psychedelic drugs has generally mandated the video recording of therapy sessions. In this paper, I address a gap in the literature by investigating ethical issues related to video recording in the unique context of psychedelic therapy sessions. I begin by summarizing the important benefits and risks related to video recording. I then examine ethical concerns about mandatory recording of psychedelic therapy sessions from a patient perspective and argue that these concerns must be taken seriously by clinicians and researchers. I also examine the view that video recording is essential for clinician safety. Given the legitimacy of concerns from both perspectives, I outline some basic informed consent considerations that could generate dialogue around potential patient concerns and defend the option to opt-out for both patients and clinicians. In conclusion, I underscore the importance of further critical bioethical inquiry and qualitative research regarding video recording practices in the context of psychedelic-assisted therapies.
... The dramatic changes in consciousness produced by a psychedelic can be accompanied by the surfacing of repressed psychological content, intensified emotions (fear, confusion, paranoia, awe, gratitude, joy, etc), sudden changes in core beliefs, ego death or ego inflation, unprecedented stillness or invigorated motivation, and other amplified emotional and behavioral changes (Carhart-Harris, 2013;Ortigo and Richards, 2021;Timmermann et al., 2021). The dissipation of emotional extremes and return to internal stability and a feeling of settledness naturally tends to occur as the acute effects of a psychedelic subside, though in some cases imbalances may persist (Carhart-Harris and Friston, 2019). ...
In this study, we describe the development and initial validation of two psychometric scales for measuring psychedelic integration. Psychedelic integration refers to the post-acute period of time following psychedelic drug administration. We created the Integration Engagement Scale (IES) to capture positive behavioral engagement with integration and the Experienced Integration Scale (EIS) to capture internal aspects of feeling integrated. These scales were developed to measure post-acute psychedelic administration dynamics in order to inform the creation of enhanced integration support and to help refine a general conceptual understanding of the construct of psychedelic integration. The scales are brief and face valid instruments designed for practical use in applied and research settings. Scale items were generated and refined using the Iterative Process Model of scale development, with input from psychedelics experts and clinicians. Content validity, internal structure, and reliability were assessed via expert surveys, content validity analysis, cognitive interviewing, convergent validity analysis, exploratory factor analysis, and confirmatory factor analysis. The data indicates the scales are valid and reliable measurements of the behavioral and experiential forms of Psychedelic Integration.
... This notion is based on the observation that psychedelics tend to intensify mental phenomena and amplify their significance, presenting them as being larger and more dramatic than they would have been without psychedelics (Grof, 1994;Hartogsohn, 2018). It is thought that this leads to a "manifestation of otherwise latent psychological processes" (Grof, 1994, p. 11), an increase in magical thinking (Carhart-Harris, 2013), and meaningenhancement that is crucial in therapeutic work (Hartogsohn, 2018). As with any substance, the concept of Set and Setting plays an important role in psychedelic experiences; set here refers to intentions, expectations and the experiencer's overall state of mind, while setting refers to the environment in which psychedelic use takes place (World Health Organization, 1958;Leary et al., 2000;Hartogsohn, 2016Hartogsohn, , 2017. ...
Psychedelic Harm Reduction and Integration (PHRI) is a transtheoretical and transdiagnostic clinical approach to working with patients who are using or considering using psychedelics in any context. The ongoing discussion of psychedelics in academic research and mainstream media, coupled with recent law enforcement deprioritization of psychedelics and compassionate use approvals for psychedelic-assisted therapy, make this model exceedingly timely. Given the prevalence of psychedelic use, the therapeutic potential of psychedelics, and the unique cultural and historical context in which psychedelics are placed, it is important that mental health providers have an understanding of the unique motivations, experiences, and needs of people who use them. PHRI incorporates elements of harm reduction psychotherapy and psychedelic-assisted psychotherapy, and can be applied in both brief and ongoing psychotherapy interactions. PHRI represents a shift away from assessment limited to untoward outcomes of psychedelic use and abstinence-based addiction treatment paradigms and toward a stance of compassionate, destigmatizing acceptance of patients' choices. Considerations for assessment, preparation, and working with difficult experiences are presented.
... Indeed, despite the longstanding conception of psychedelics as "psychotomimetic" (psychosis-mimicking) drugs (Sessa 2012), a growing body of evidence suggests that psychedelic experiences, especially in controlled conditions, are associated with improved mental health outcomes (Johansen andKrebs 2015, dos Santos et al. 2016). It is true that acute psychedelic intoxication involves increased suggestibility and tendencies towards magical thinking , Carhart-Harris 2013. ...
Can there be phenomenal consciousness without self-consciousness? Strong intuitions and prominent theories of consciousness say “no”: experience requires minimal self-awareness, or "subjectivity". This “subjectivity principle” (SP) faces apparent counterexamples in the form of anomalous mental states claimed to lack self-consciousness entirely, such as “inserted thoughts” in schizophrenia and certain mental states in depersonalization disorder (DPD). However, Billon and Kriegel (2015) have defended SP by arguing (inter alia) that while some of these mental states may be totally selfless, those states are not phenomenally conscious and thus do not constitute genuine counterexamples to SP.
I argue that this defence cannot work in relation to certain experiences of ego dissolution induced by potent fast-acting serotonergic psychedelics. These mental states jointly instantiate the two features whose co-instantiation by a single mental state SP prohibits: (a) phenomenal consciousness and (b) total lack of self-consciousness.
One possible objection is that these mental states may lack "me-ness" and "mineness" but cannot lack “for-me-ness”, a special inner awareness of mental states by the self. In response I propose a dilemma. For-me-ness can be defined either as containing a genuinely experiential component or as not. On the first horn, for-me-ness is clearly absent (I argue) from my counterexamples. On the second horn, for-me-ness been defined in a way that conflicts with the claims and methods of its proponents, and the claim that phenomenally conscious mental states can totally lack self-consciousness has been conceded. I conclude with some reflections on the intuitive plausibility of SP in light of evidence from altered states.
... In psychotic personality organization, on a psychological level it is possible to find diffusion of identity (not integrated and fragmented), primitive defense mechanism, and loss of reality testing; on a neurobiological level we find disturbance at a level of self-constitution, a disruption in the global organization of the brain's intrinsic activity: whole topography over all networks and frequency range are disrupted, and, for instance, the usual negative correlations between the default mode network (DMN) and the control executive network (CEN) that are usually characterized by an anticorrelation are in psychosis transformed into a positive correlation which in turn may lead to the breakdown of the rest-self overlap where there is a self-assignment to either internal or external stimuli (Carhart-Harris 2013;Carhart-Harris et al. 2014). In this case we may hypothesize that there is no possibility to differentiate the internal world from the external reality; there is a fragmentation of the perception of time and space, which results in the identity diffusion or fragmentation of self-constitution. ...
Personality is a complex construct that is closely related to the subjective experiences between internal world and external reality, a sense of subjectivity that is referred to the concept of self in psychiatry and psychodynamic literature.
The sense of self is a foundational element of neurotypical human consciousness. We normally experience the world as embodied agents, with the unified sensation of our selfhood being nested in our body. Critically, the sense of self can be altered in psychiatric conditions such as psychosis and altered states of consciousness induced by psychedelic compounds. The similarity of phenomenological effects across psychosis and psychedelic experiences has given rise to the “psychotomimetic” theory suggesting that psychedelics simulate psychosis-like states. Moreover, psychedelic-induced changes in the sense of self have been related to reported improvements in mental health. Here we investigated the bodily self in psychedelic, psychiatric, and control populations. Using the Moving Rubber Hand Illusion, we tested (N = 75) patients with psychosis, participants with a history of substantial psychedelic experiences, and control participants to see how psychedelic and psychiatric experience impacts the bodily self. Results revealed that psychosis patients had reduced Body Ownership and Sense of Agency during volitional action. The psychedelic group reported subjective long-lasting changes to the sense of self, but no differences between control and psychedelic participants were found. Our results suggest that while psychedelics induce both acute and enduring subjective changes in the sense of self, these are not manifested at the level of the bodily self. Furthermore, our data show that bodily self-processing, related to volitional action, is disrupted in psychosis patients. We discuss these findings in relation to anomalous self-processing across psychedelic and psychotic experiences.
A increasing number of studies points toward beneficial effects of psychedelic experiences if administered in the right setting. A smaller number of studies present explanations for why psychedelics have these therapeutic effects. Of these most argue that psychedelic experiences increase neuroplasticity, allowing subjects to let go of unhelpful entrenched beliefs. I argue that (1) psychedelics are likely therapeutic because they help subjects align their beliefs with their respective contexts; (2) relaxation of entrenched beliefs need not occur at higher cognitive levels concerned with the self or ego to be therapeutic; and (3) the proneness toward having supernatural entity experiences can be explained using this contextual approach. I conclude that therapeutic effects of psychedelics are not necessarily tied to beliefs about the self.
Objective: Reports have indicated possible uses of ayahuasca for the treatment of conditions including depression, addictions, post-traumatic stress disorder, anxiety and specific psychoneuroendocrine immune system pathologies. The article assesses potential ayahuasca and N,N-dimethyltryptamine (DMT) integration with contemporary healthcare. The review also seeks to provide a summary of selected literature regarding the mechanisms of action of DMT and ayahuasca; and assess to what extent the state of research can explain reports of unusual phenomenology.
Design: A narrative review.
Results: Compounds in ayahuasca have been found to bind to serotonergic receptors , glutaminergic receptors, sigma-1 receptors, trace amine-associated receptors , and modulate BDNF expression and the dopaminergic system. Subjective effects are associated with increased delta and theta oscillations in amygdala and hippocampal regions, decreased alpha wave activity in the default mode network, and stimulations of vision-related brain regions particularly in the visual association cortex. Both biological processes and field of consciousness models have been proposed to explain subjective effects of DMT and ayahuasca, however, the evidence supporting the proposed models is not sufficient to make confident conclusions. Ayahuasca plant medicine and DMT represent potentially novel treatment modalities.
Conclusions: Further research is required to clarify the mechanisms of action and develop treatments which can be made available to the general public. Integration between healthcare research institutions and reputable practitioners in the Amazon is recommended.
Having established the basic parameters of human visual perception, it’s time to return to the analogy of how ghostly energy can be comprehended, and the notion of the human visual system as an instrument.
Past research has demonstrated to the ability of psychedelics to enhance suggestibility, and pointed to their ability to amplify perception of meaning. This paper examines the existing evidence for the meaning-enhancing properties of psychedelics, and argues that the tendency of these agents to enhance the perception of significance offers valuable clues to explaining their reported ability to stimulate a variety of therapeutic processes, enhance creativity, and instigate mystical-type experiences. Building upon previous research, which suggested the potential role of psychedelic meaning-enhancement in enhancing placebo response, the paper explores the mechanisms by which the meaning-amplifying properties of psychedelics might also play a role in enhancing creativity, as well as in effecting mystical-type experiences. The wider social and public-health implications of this hypothesis are discussed, and suggestions are made as to the various ways in which scientific understanding of the meaning-enhancing properties of psychedelics might be advanced and utilized.
Although psilocybin has been used for centuries for religious purposes, little is known scientifically about its acute and persisting effects.
This double-blind study evaluated the acute and longer-term psychological effects of a high dose of psilocybin relative to a comparison compound administered under comfortable, supportive conditions.
The participants were hallucinogen-naïve adults reporting regular participation in religious or spiritual activities. Two or three sessions were conducted at 2-month intervals. Thirty volunteers received orally administered psilocybin (30 mg/70 kg) and methylphenidate hydrochloride (40 mg/70 kg) in counterbalanced order. To obscure the study design, six additional volunteers received methylphenidate in the first two sessions and unblinded psilocybin in a third session. The 8-h sessions were conducted individually. Volunteers were encouraged to close their eyes and direct their attention inward. Study monitors rated volunteers' behavior during sessions. Volunteers completed questionnaires assessing drug effects and mystical experience immediately after and 2 months after sessions. Community observers rated changes in the volunteer's attitudes and behavior.
Psilocybin produced a range of acute perceptual changes, subjective experiences, and labile moods including anxiety. Psilocybin also increased measures of mystical experience. At 2 months, the volunteers rated the psilocybin experience as having substantial personal meaning and spiritual significance and attributed to the experience sustained positive changes in attitudes and behavior consistent with changes rated by community observers.
When administered under supportive conditions, psilocybin occasioned experiences similar to spontaneously occurring mystical experiences. The ability to occasion such experiences prospectively will allow rigorous scientific investigations of their causes and consequences.
Psilocybin is a classic psychedelic and a candidate drug model of psychosis. This study measured the effects of psilocybin on resting-state network and thalamocortical functional connectivity (FC) using functional magnetic resonance imaging (fMRI). Fifteen healthy volunteers received intravenous infusions of psilocybin and placebo in 2 task-free resting-state scans. Primary analyses focused on changes in FC between the default-mode- (DMN) and task-positive network (TPN). Spontaneous activity in the DMN is orthogonal to spontaneous activity in the TPN, and it is well known that these networks support very different functions (ie, the DMN supports introspection, whereas the TPN supports externally focused attention). Here, independent components and seed-based FC analyses revealed increased DMN-TPN FC and so decreased DMN-TPN orthogonality after psilocybin. Increased DMN-TPN FC has been found in psychosis and meditatory states, which share some phenomenological similarities with the psychedelic state. Increased DMN-TPN FC has also been observed in sedation, as has decreased thalamocortical FC, but here we found preserved thalamocortical FC after psilocybin. Thus, we propose that thalamocortical FC may be related to arousal, whereas DMN-TPN FC is related to the separateness of internally and externally focused states. We suggest that this orthogonality is compromised in early psychosis, explaining similarities between its phenomenology and that of the psychedelic state and supporting the utility of psilocybin as a model of early psychosis.
A large body of evidence, including longitudinal analyses of personality change, suggests that core personality traits are predominantly stable after age 30. To our knowledge, no study has demonstrated changes in personality in healthy adults after an experimentally manipulated discrete event. Intriguingly, double-blind controlled studies have shown that the classic hallucinogen psilocybin occasions personally and spiritually significant mystical experiences that predict long-term changes in behaviors, attitudes and values. In the present report we assessed the effect of psilocybin on changes in the five broad domains of personality - Neuroticism, Extroversion, Openness, Agreeableness, and Conscientiousness. Consistent with participant claims of hallucinogen-occasioned increases in aesthetic appreciation, imagination, and creativity, we found significant increases in Openness following a high-dose psilocybin session. In participants who had mystical experiences during their psilocybin session, Openness remained significantly higher than baseline more than 1 year after the session. The findings suggest a specific role for psilocybin and mystical-type experiences in adult personality change.
Overactivation of serotonin (5-hydroxytryptamine, 5-HT)(2A) receptors causes impulsivity and attentional deficits. Since 5-HT(2A) receptors are known to entertain antagonistic interactions with metabotropic glutamate (mGlu)2/3 receptors, this interaction may provide an alternative target for a novel class of antipsychotics.
The study characterizes interactions between 5-HT(2A) and mGlu2/3 receptors implicated in impulse control. Hooded Lister rats were trained in a 5-choice serial reaction time task (5-CSRTT) and treated with the 5-HT(2A/2C) receptor agonist (±)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropan hydrochloride (DOI, 0.1 mg/kg) and the mGlu2/3 receptor agonist LY379268 (1 mg/kg). In addition, associated drug-induced changes in neuronal activity were assessed via c-Fos immunoreactivity (Fos IR), and co-localization of c-Fos and GABAergic markers was detected using double immunofluorescence labeling.
Systemic DOI caused impulsive overresponding that was attenuated in animals pre-treated with LY379268. LY379268 itself had no significant effect on the rats' performance in the 5-CSRTT. DOI enhanced Fos IR within fronto-cortical and limbic brain structures, and this effect was blocked by LY379268 pre-treatment. Double immunofluorescence labeling showed a specific co-localization of DOI-elicited Fos IR with GABAergic (GAD(67)-positive) cells lacking the calcium-binding protein parvalbumin while LY379268 increased Fos IR in GABAergic and non-GABAergic cells.
Our results suggest that impulsivity is possibly due to a primary increase in Glu transmission mediated via 5-HT(2A) receptor activation. Thus, mGlu2/3 receptor agonists might have some potential for treating motor impulsivity-related impairments while their cognitive enhancing effects were not confirmed in this study.