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Neuroscience

Psilocybin-Induced Decrease in Amygdala Reactivity Correlates with Enhanced Positive Mood in Healthy Volunteers

April 26, 2014 / Depression, Mushrooms / Psilocybin, Neuroscience, Papers, Psychology, Psychopharmacology, Publications / By / , , , , , ,

Abstract

Background
The amygdala is a key structure in serotonergic emotion-processing circuits. In healthy volunteers, acute administration of the serotonin 1A/2A/2C receptor agonist psilocybin reduces neural responses to negative stimuli and induces mood changes toward positive states. However, it is little-known whether psilocybin reduces amygdala reactivity to negative stimuli and whether any change in amygdala reactivity is related to mood change.

Methods
This study assessed the effects of acute administration of the hallucinogen psilocybin (.16 mg/kg) versus placebo on amygdala reactivity to negative stimuli in 25 healthy volunteers using blood oxygen level-dependent functional magnetic resonance imaging. Mood changes were assessed using the Positive and Negative Affect Schedule and the state portion of the State-Trait Anxiety Inventory. A double-blind, randomized, cross-over design was used with volunteers counterbalanced to receive psilocybin and placebo in two separate sessions at least 14 days apart.

Results
Amygdala reactivity to negative and neutral stimuli was lower after psilocybin administration than after placebo administration. The psilocybin-induced attenuation of right amygdala reactivity in response to negative stimuli was related to the psilocybin-induced increase in positive mood state.

Conclusions
These results demonstrate that acute treatment with psilocybin decreased amygdala reactivity during emotion processing and that this was associated with an increase of positive mood in healthy volunteers. These findings may be relevant to the normalization of amygdala hyperactivity and negative mood states in patients with major depression.

Kraehenmann, R., Preller, K. H., Scheidegger, M., Pokorny, T., Bosch, O. G., Seifritz, E., & Vollenwieder, F. X. (2014). Psilocybin-Induced Decrease in Amygdala Reactivity Correlates with Enhanced Positive Mood in Healthy Volunteers. Biological Psychiatry. http://dx.doi.org/10.1016/j.biopsych.2014.04.010
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Classical hallucinogens as antidepressants? A review of pharmacodynamics and putative clinical roles

March 17, 2014 / Anxiety disorders / PTSD, Depression, Mushrooms / Psilocybin, Neuroscience, Papers, Psychiatry, Psychology, Psychopharmacology, Psychotherapy, Publications / By / , , ,

Abstract

Hallucinogens have been part of spiritual practice for millennia, but controversy surrounding their mind-manifesting effects led to their proscription by the mid-20th century, largely without evidence of harm or toxicity and despite nascent data suggesting therapeutic utility in treating depressive illnesses. This review explores their pharmacodynamic actions and the current limited data on their clinic effectiveness. These drugs appear to exert their psychedelic effects through their agonist or partial agonist activity at the serotonergic 5-HT2A receptor, though they also have affinity for other metabotropic serotonin receptors. Hallucinogen binding affects a wide range of intracellular signalling pathways, the precise nature of which remains incompletely understood. They alter the serotonergic tone of brainstem raphe nuclei that project through the brain; they interact with receptors in the prefrontal cortex altering connectivity patterns and intracellular functioning; and they disrupt inhibitory control of sensory input via the thalamus to the cortex. The serotonergic system has long been implicated in anxiety and depressive disorders, and is a major target of most existing antidepressants. Classical hallucinogens alter the functioning of this system, but not in the same way current medications do: whilst there are identified receptors and neurotransmitter pathways through which hallucinogens could therein produce therapeutic effects, the neurobiology of this remains speculative at this time. There is currently an extremely limited but growing literature on hallucinogen safety and clinical application. The drugs appear well tolerated by healthy controls and clinical populations, and the rapid tolerance to repeated administration might reduce the possibility of dependency. Clinical trials reported over the past decade have generally shown positive therapeutic potential, but they are notably few in number. Legislative policy has had a freezing effect on evaluation of these compounds, a better understanding of which might improve our knowledge of the processes involved in consciousness, the neuropathology of depression, and potentially open up new pharmacological therapies.

Baumeister, D., Barnes, G., Giaroli, G., & Tracy, D. (2014). Classical hallucinogens as antidepressants? A review of pharmacodynamics and putative clinical roles. Therapeutic Advances in Psychopharmacology, 4(4), 156-159. http://dx.doi.org/10.1177/2045125314527985
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Therapeutic Effects of Ritual Ayahuasca Use in the Treatment of Substance Dependence—Qualitative Results

March 11, 2014 / Addiction, Ayahuasca, Ethnobotany, Neuroscience, Papers, Phenomenology, Psychology, Psychotherapy, Publications, Safety, Spirituality, Toxicology / By / ,

Abstract

This qualitative empirical study explores the ritual use of ayahuasca in the treatment of addictions. Ayahuasca is an Amazonian psychedelic plant compound created from an admixture of the vine Banisteriopsis caapi and the bush Psychotria viridis. The study included interviews with 13 therapists who apply ayahuasca professionally in the treatment of addictions (four indigenous healers and nine Western mental health professionals with university degrees), two expert researchers, and 14 individuals who had undergone ayahuasca-assisted therapy for addictions in diverse contexts in South America. The study provides empirically based hypotheses on therapeutic mechanisms of ayahuasca in substance dependence treatment. Findings indicate that ayahuasca can serve as a valuable therapeutic tool that, in carefully structured settings, can catalyze neurobiological and psychological processes that support recovery from substance dependencies and the prevention of relapse. Treatment outcomes, however, can be influenced by a number of variables that are explained in this study. In addition, issues related to ritual transfer and strategies for minimizing undesired side-effects are discussed.

Loizaga-Velder, A., & Verres, R. (2014). Therapeutic Effects of Ritual Ayahuasca Use in the Treatment of Substance Dependence—Qualitative Results. Journal of Psychoactive Drugs, 46(1), 63–72. http://dx.doi.org/10.1080/02791072.2013.873157
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MDMA and the “Ecstasy Paradigm”

March 11, 2014 / MDMA, Neuroscience, Papers, Psychiatry, Psychology, Psychopharmacology, Publications, Safety, Sociology, Toxicology / By /

Abstract

For nearly 30 years, there has been a steady flow of research papers highlighting the dangers of MDMA and the implications for ecstasy users. After such a long time, it would be reasonable to expect that these dangers would be obvious due to the large number of ecstasy users. The available evidence does not indicate that there are millions of ecstasy users experiencing any problems linked to their ecstasy use. The “precautionary principle” suggests that, in the absence of knowing for certain, “experts” should argue that MDMA be avoided. However, this may have been taken too far, as the dire warnings do not seem to be reducing with the lack of epidemiological evidence of clinically relevant problems. The “ecstasy paradigm” is one way of articulating this situation, in that the needs of research funders and publication bias lead to a specific set of subcultural norms around what information is acceptable in the public domain. By digging a little deeper, it is easy to find problems with the evidence base that informs the public debate around MDMA. The key question is whether it is acceptable to maintain this status quo given the therapeutic potential of MDMA.

Cole, J. C. (2014). MDMA and the “Ecstasy Paradigm”. Journal of Psychoactive Drugs, 46(1), 44–56. http://dx.doi.org/10.1080/02791072.2014.878148
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The Potential Dangers of Using MDMA for Psychotherapy

March 11, 2014 / Anxiety disorders / PTSD, MDMA, Neuroscience, Papers, Psychiatry, Psychology, Psychopharmacology, Psychotherapy, Publications, Safety, Toxicology / By /

Abstract

MDMA has properties that may make it attractive for psychotherapy, although many of its effects are potentially problematic. These contrasting effects will be critically reviewed in order to assess whether MDMA could be safe for clinical usage. Early studies from the 1980s noted that MDMA was an entactogen, engendering feelings of love and warmth. However, negative experiences can also occur with MDMA since it is not selective in the thoughts or emotions it releases. This unpredictability in the psychological material released is similar to another serotonergic drug, LSD. Acute MDMA has powerful neurohormonal effects, increasing cortisol, oxytocin, testosterone, and other hormone levels. The release of oxytocin may facilitate psychotherapy, whereas cortisol may increase stress and be counterproductive. MDMA administration is followed by a period of neurochemical recovery, when low serotonin levels are often accompanied by lethargy and depression. Regular usage can also lead to serotonergic neurotoxicity, memory problems, and other psychobiological problems. Proponents of MDMA-assisted therapy state that it should only be used for reactive disorders (such as PTSD) since it can exacerbate distress in those with a prior psychiatric history. Overall, many issues need to be considered when debating the relative benefits and dangers of using MDMA for psychotherapy.

Parrott, A. C. (2014). The Potential Dangers of Using MDMA for Psychotherapy. Journal of Psychoactive Drugs, 46(1) , 37–43. http://dx.doi.org/10.1080/02791072.2014.873690
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Therapeutic infusions of ketamine: Do the psychoactive effects matter?

February 18, 2014 / Addiction, Consciousness, Ketamine, Medicine, Neuroscience, Other disciplines, Other subjects, Papers, Personal development, Psychiatry, Psychology, Psychopharmacology, Psychotherapy, Publications / By / , , , , ,

Abstract

Background

Sub-anesthetic ketamine infusions may benefit a variety of psychiatric disorders, including addiction. Though ketamine engenders transient alterations in consciousness, it is not known whether these alterations influence efficacy. This analysis evaluates the mystical-type effects of ketamine, which may have therapeutic potential according to prior research, and assesses whether these effects mediate improvements in dependence-related deficits, 24 h postinfusion.

Methods

Eight cocaine dependent individuals completed this double-blind, randomized, inpatient study. Three counter-balanced infusions separated by 48 h were received: lorazepam (2 mg) and two doses of ketamine (0.41 mg/kg and 0.71 mg/kg, with the former dose always preceding the latter). Infusions were followed within 15 min by measures of dissociation (Clinician Administered Dissociative Symptoms Scale: CADSS) and mystical-type effects (adapted from Hood’s Mysticism Scale: HMS). At baseline and 24 h postinfusion, participants underwent assessments of motivation to stop cocaine (University of Rhode Island Change Assessment) and cue-induced craving (by visual analogue scale for cocaine craving during cue exposure).

Results

Ketamine led to significantly greater acute mystical-type effects (by HMS) relative to the active control lorazepam; ketamine 0.71 mg/kg was associated with significantly higher HMS scores than was the 0.41 mg/kg dose. HMS score, but not CADSS score, was found to mediate the effect of ketamine on motivation to quit cocaine 24 h postinfusion.

Conclusions

These findings suggest that psychological mechanisms may be involved in some of the anti-addiction benefits resulting from ketamine. Future research can evaluate whether the psychoactive effects of ketamine influence improvements in larger samples.

Dakwar, E., Anerella, C., Hart, C. L., Levin, F. R., Mathew, S. J., & Nunes, E. V. (2014). Therapeutic infusions of ketamine: Do the psychoactive effects matter?. Drug and alcohol dependence, 136, 153-157. http://dx.doi.org/10.1016/j.drugalcdep.2013.12.019

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Do the dissociative side effects of ketamine mediate its antidepressant effects?

February 18, 2014 / Depression, Ketamine, Medicine, Neuroscience, Other subjects, Papers, Psychiatry, Psychology, Psychopharmacology, Psychotherapy, Publications / By / , , , , , , ,

Abstract

Background

The N-methyl-d-aspartate receptor antagonist ketamine has rapid antidepressant effects in major depression. Psychotomimetic symptoms, dissociation and hemodynamic changes are known side effects of ketamine, but it is unclear if these side effects relate to its antidepressant efficacy.

Methods

Data from 108 treatment-resistant inpatients meeting criteria for major depressive disorder and bipolar disorder who received a single subanesthetic ketamine infusion were analyzed. Pearson correlations were performed to examine potential associations between rapid changes in dissociation and psychotomimesis with the Clinician-Administered Dissociative States Scale (CADSS) and Brief Psychiatric Rating Scale (BPRS), respectively, manic symptoms with Young Mania Rating Scale (YMRS), and vital sign changes, with percent change in the 17-item Hamilton Depression Rating scale (HDRS) at 40 and 230 min and Days 1 and 7.

Results

Pearson correlations showed significant association between increased CADSS score at 40 min and percent improvement with ketamine in HDRS at 230 min (r=−0.35, p=0.007) and Day 7 (r=−0.41, p=0.01). Changes in YMRS or BPRS Positive Symptom score at 40 min were not significantly correlated with percent HDRS improvement at any time point with ketamine. Changes in systolic blood pressure, diastolic blood pressure, and pulse were also not significantly related to HDRS change.

Limitations

Secondary data analysis, combined diagnostic groups, potential unblinding.

Conclusions

Among the examined mediators of ketamine׳s antidepressant response, only dissociative side effects predicted a more robust and sustained antidepressant. Prospective, mechanistic investigations are critically needed to understand why intra-infusion dissociation correlates with a more robust antidepressant efficacy of ketamine.

Luckenbaugh, D. A., Niciu, M. J., Ionescu, D. F., Nolan, N. M., Richards, E. M., Brutsche, N. E., … & Zarate, C. A. (2014). Do the dissociative side effects of ketamine mediate its antidepressant effects?. Journal of affective disorders, 159, 56-61. http://dx.doi.org/10.1016/j.jad.2014.02.017

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The entropic brain: a theory of conscious states informed by neuroimaging research with psychedelic drugs

February 3, 2014 / Consciousness, LSD, Mushrooms / Psilocybin, Neuroscience, Papers, Psychology, Psychopharmacology, Publications / By / , , , , , , ,

Abstract

Entropy is a dimensionless quantity that is used for measuring uncertainty about the state of a system but it can also imply physical qualities, where high entropy is synonymous with high disorder. Entropy is applied here in the context of states of consciousness and their associated neurodynamics, with a particular focus on the psychedelic state. The psychedelic state is considered an exemplar of a primitive or primary state of consciousness that preceded the development of modern, adult, human, normal waking consciousness. Based on neuroimaging data with psilocybin, a classic psychedelic drug, it is argued that the defining feature of “primary states” is elevated entropy in certain aspects of brain function, such as the repertoire of functional connectivity motifs that form and fragment across time. Indeed, since there is a greater repertoire of connectivity motifs in the psychedelic state than in normal waking consciousness, this implies that primary states may exhibit “criticality,” i.e., the property of being poised at a “critical” point in a transition zone between order and disorder where certain phenomena such as power-law scaling appear. Moreover, if primary states are critical, then this suggests that entropy is suppressed in normal waking consciousness, meaning that the brain operates just below criticality. It is argued that this entropy suppression furnishes normal waking consciousness with a constrained quality and associated metacognitive functions, including reality-testing and self-awareness. It is also proposed that entry into primary states depends on a collapse of the normally highly organized activity within the default-mode network (DMN) and a decoupling between the DMN and the medial temporal lobes (which are normally significantly coupled). These hypotheses can be tested by examining brain activity and associated cognition in other candidate primary states such as rapid eye movement (REM) sleep and early psychosis and comparing these with non-primary states such as normal waking consciousness and the anaesthetized state.

Carhart-Harris, R. L., Leech, R., Hellyer, P. J., Shanahan, M., Feilding, A., Tagliazucchi, E., Chialvo, D. R., & Nutt, D. (2014). The entropic brain: a theory of conscious states informed by neuroimaging research with psychedelic drugs. Frontiers in Human Neuroscience, 8, 1-22. http://dx.doi.org/10.3389/fnhum.2014.00020
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The Effects of Acutely Administered 3,4-Methylenedioxymethamphetamine on Spontaneous Brain Function in Healthy Volunteers Measured with Arterial Spin Labelling and Blood Oxygen Level-Dependent Resting-State Functional Connectivity

January 10, 2014 / MDMA, Neuroscience, Other subjects, Papers, Psychology, Psychopharmacology, Publications / By / , , , , , ,

Abstract

Background
3,4-methylenedioxymethamphetamine (MDMA) is a potent monoamine releaser that produces an acute euphoria in most individuals.

Methods
MDMA was orally administered to 25 physically and mentally healthy individuals in a double-blind, placebo-controlled, balanced-order study. Arterial spin labelling (ASL) and seed-based resting state functional connectivity (RSFC) were used to produce spatial maps displaying changes in cerebral blood flow (CBF) and RSFC after MDMA. Participants underwent two ASL and two BOLD scans in a 90 minute scanning session and the MDMA and placebo study days were separated by one week.

Results
MDMA produced marked increases in positive mood. Only decreased CBF was observed after MDMA and this was localised to the right medial temporal lobe (MTL), thalamus, inferior visual cortex and the somatosensory cortex. Decreased CBF in the right amygdala and hippocampus correlated with ratings of the intensity of MDMA’s global subjective effects. The RSFC results complemented the CBF results, with decreases in RSFC between midline cortical regions, the medial prefrontal cortex and MTL regions, and increases between the amygdala and hippocampus. There were trend-level correlations between these effects and ratings of intense and positive subjective effects.

Conclusions
The MTLs appear to be specifically implicated in the mechanism of action of MDMA but further work is required to elucidate how the drug’s characteristic subjective effects arise from its modulation of spontaneous brain activity.

Carhart-Harris, R. L., Murphy, K., Leech, R., Erritzoe, D., Wall, M. B., Ferguson, B., … Nutt, D. J. (2014). The Effects of Acutely Administered 3,4-Methylenedioxymethamphetamine on Spontaneous Brain Function in Healthy Volunteers Measured with Arterial Spin Labelling and Blood Oxygen Level-Dependent Resting-State Functional Connectivity. Biological Psychiatry. http://dx.doi.org/10.1016/j.biopsych.2013.12.015
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Psilocybin – Summary of knowledge and new perspectives

December 17, 2013 / Addiction, Anxiety disorders / PTSD, Chemistry, Cluster headache, Depression, HPPD, Mushrooms / Psilocybin, Mystical experiences, Neuroscience, Papers, Personality, Phenomenology, Psychiatry, Psychology, Psychopharmacology, Psychosis, Psychotherapy, Publications, Safety, Spirituality, Toxicology / By / , ,

Abstract

Psilocybin, a psychoactive alkaloid contained in hallucinogenic mushrooms, is nowadays given a lot of attention in the scientific community as a research tool for modeling psychosis as well as due to its potential therapeutic effects. However, it is also a very popular and frequently abused natural hallucinogen. This review summarizes all the past and recent knowledge on psilocybin. It briefly deals with its history, discusses the pharmacokinetics and pharmacodynamics, and compares its action in humans and animals. It attempts to describe the mechanism of psychedelic effects and objectify its action using modern imaging and psychometric methods. Finally, it describes its therapeutic and abuse potential.

Tylš, F., Páleníček, T., & Horáček, J. (2014). Psilocybin – Summary of knowledge and new perspectives. European Neuropsychopharmacology, 24, 342-365. http://dx.doi.org/10.1016/j.euroneuro.2013.12.006

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