Journal of Psychopharmacology
September 28, 2011
Katherine A Maclean, Matthew W Johnson, Roland R Griffiths
907 citations
Core personality traits are generally stable after age 30, but a high dose of the hallucinogen psilocybin can increase Openness to experience in healthy adults. In a double-blind controlled study, participants who had a mystical experience during their psilocybin session showed significantly higher Openness than baseline, and this increase persisted for more than a year. The findings suggest that psilocybin and mystical-type experiences can produce lasting personality change in adults.
Psychological science
June 1, 2010
Katherine A Maclean, Emilio Ferrer, Stephen R Aichele et al.
625 citations
Voluntary attention cannot be sustained for long periods, leading to a decline in perceptual sensitivity called the vigilance decrement. Training involving meditation practice—about 5 hours daily for 3 months—improved sustained attention. Participants were randomly assigned to receive training first or serve as waiting-list controls. Training improved visual discrimination, linked to increases in perceptual sensitivity and vigilance during sustained visual attention. These results suggest that perceptual improvements reduce the resource demand of target discrimination, making it easier to sustain voluntary attention.
Psychoneuroendocrinology
June 1, 2011
Tonya L Jacobs, Elissa S Epel, Jue Lin et al.
435 citations
After a 3-month meditation retreat with about 6 hours of daily practice, retreat participants showed greater telomerase activity—an indicator of cellular longevity—compared to a matched wait-list control group. Retreat participants also reported increased Perceived Control, Mindfulness, and Purpose in Life, and decreased Neuroticism. Statistical mediation analyses suggested that the retreat's effect on telomerase activity was explained by increases in Perceived Control and decreases in Neuroticism. These changes in perceived control and neuroticism were themselves partially explained by increased Mindfulness and Purpose in Life. Purpose in Life also directly mediated the group difference in telomerase activity, whereas Mindfulness did not. The findings suggest that meditation may influence cellular health through psychological changes.
Emotion (Washington, D.C.)
April 1, 2011
Baljinder K Sahdra, Katherine A Maclean, Emilio Ferrer et al.
203 citations
Three months of intensive meditation training in an isolated retreat setting improved sustained self-regulatory control, measured by a response inhibition task, and adaptive socioemotional functioning, a latent factor combining measures of attachment, mindfulness, empathy, personality traits, emotion regulation, depression, anxiety, and well-being. A wait-list control group showed no improvement until they underwent the same training. Gains in both self-regulation and adaptive functioning were sustained at a 5-month follow-up. Dynamic modeling indicated that improvements in self-regulation drove later changes in adaptive functioning, supporting the Buddhist claim that enhanced self-regulation is a precursor to emotional well-being.
Frontiers in human neuroscience
January 1, 2012
Manish Saggar, Brandon G King, Anthony P Zanesco et al.
136 citations
Intensive meditation training produces replicable changes in brainwave activity. In a controlled study, participants who practiced focused attention meditation for three months showed reduced beta-band power over anterior and posterior scalp regions during meditation, compared to a wait-list group that later received identical training. Individual alpha frequency also decreased across both retreats, and the decrease was directly related to the amount of meditation practice. These longitudinal changes in brain oscillatory activity help explain how meditation may support long-term improvements in attention and cognition.
Psychopharmacology
March 1, 2013
Katherine A Maclean, Matthew W Johnson, Chad J Reissig et al.
134 citations
Inhaled salvinorin A, the active compound in Salvia divinorum, produces intense, dose-related subjective and cognitive effects that peak within 2 minutes and rapidly dissipate. In eight healthy adults with hallucinogen experience, high doses frequently caused maximal drug strength ratings or unresponsiveness. The compound induced dissociative effects and impaired recall and recognition memory, with some overlap with classic hallucinogens but a qualitatively distinct profile. No persisting adverse effects were observed at one-month follow-up. These findings contribute to understanding the kappa opioid system and may inform future therapeutic applications.
Drug and alcohol dependence
May 1, 2011
Matthew W Johnson, Katherine A Maclean, Chad J Reissig et al.
134 citations
Salvinorin A, the psychoactive compound in Salvia divinorum, produces rapid, dose-dependent subjective effects that peak at 2 minutes and subside within 20 minutes after inhalation. In a double-blind, placebo-controlled study with 4 healthy hallucinogen-using adults, doses from 0.375 to 21 μg/kg increased ratings of mystical-type experiences and effects similar to classic hallucinogens. Salvinorin A did not significantly raise heart rate or blood pressure. Participants reported intense experiences involving altered spatial orientation, pressure on the body, childhood memories, cartoon-like imagery, and contact with entities. The findings suggest salvinorin A has a unique profile that includes mystical-type effects.
PloS one
January 1, 2014
Donal G Maccoon, Katherine A Maclean, Richard J Davidson et al.
97 citations
Eight weeks of mindfulness-based stress reduction (MBSR) training did not improve sustained attention more than an active control program (Health Enhancement Program, HEP) in a randomized trial with 63 community participants. The study used a visual continuous performance task to measure attention. Although the main hypotheses were not confirmed, some evidence suggested improved visual discrimination similar to effects seen in other research. Attentional sensitivity was not affected by MBSR, and it remains unclear whether mindfulness might positively affect vigilance. The results highlight procedural modifications needed for future research on sustained attention in similar samples.
Frontiers in human neuroscience
January 1, 2013
Anthony P Zanesco, Brandon G King, Katherine A Maclean et al.
96 citations
One month of intensive daily Vipassana meditation training improved executive control on a 32-minute response inhibition task. Trained participants showed better accuracy and reduced reaction time variability compared to matched controls. They also reported increased concentration during the task, but not changes in effort or motivation. Higher concentration ratings predicted lower reaction time variability, linking subjective concentrative engagement with objective attentional stability. The findings support contemplative claims that meditation leads to stable, clear attentional focus and suggest that meditators accurately perceive their improved cognitive performance.
Emotion (Washington, D.C.)
December 1, 2015
Erika L Rosenberg, Anthony P Zanesco, Brandon G King et al.
77 citations
Three months of intensive meditation training—daily practice in attention and compassion techniques—alters emotional responses to human suffering. In a randomized trial, 60 participants were assigned to either a meditation retreat or a wait-list control. At post-training, those who meditated showed more facial expressions of sadness and fewer expressions of anger, contempt, and disgust when viewing film scenes of suffering, compared to controls. Self-reported sympathy, but not sadness or distress, predicted these sad expressions and reduced rejection emotions in the training group. The results suggest that intensive meditation fosters enhanced sympathetic concern for others and reduced aversion to their suffering.
Health psychology : official journal of the Division of Health Psychology, American Psychological Association
October 1, 2013
Tonya L Jacobs, Phillip R Shaver, Elissa S Epel et al.
62 citations
Cognitive perseverations such as worry and rumination may prolong cortisol release, potentially contributing to disease pathways. Meditation training can increase self-reported mindfulness, which is linked to reductions in such perseverations, but no prior work directly linked mindfulness to resting cortisol output. In an observational study of 57 adults on a 3-month meditation retreat, mindfulness increased from pre- to post-retreat, while cortisol did not significantly change overall. However, mindfulness was inversely related to evening cortisol at both time points, and larger increases in mindfulness were associated with decreases in cortisol, whereas smaller increases or slight decreases in mindfulness were linked to increases in cortisol. These findings suggest a relationship between self-reported mindfulness and resting output of the hypothalamic-pituitary-adrenal system.
Journal of cognitive neuroscience
August 1, 2019
Anthony P Zanesco, Brandon G King, Chivon Powers et al.
40 citations
Improvements in perceptual discrimination from intensive meditation training can alter brain signals related to attention and perception, but only when the task difficulty is fixed rather than adjusted to match the person's improving ability. In two three-month meditation retreats, participants performed a continuous visual task while brain activity was recorded. When the target difficulty was held constant, training reduced declines in early sensory processing and shifted the timing of those brain signals. Changes in later processing stages correlated with better perceptual thresholds. No such brain changes occurred when task difficulty was increased to keep pace with participants' improving skill. The findings show that directed mental training can modify electrophysiological markers of attention and perception, depending on how task demands relate to the individual's capacity.
NeuroImage
July 1, 2015
Manish Saggar, Anthony P Zanesco, Brandon G King et al.
31 citations
Intensive meditation training alters brain dynamics by increasing the delay between cortical and thalamic cells and reducing inhibitory connections within the thalamus. These changes, identified through computational modeling of EEG data from two 3-month meditation retreats, provide a neural mechanism for the previously observed slowing of individual alpha frequency. The reduced thalamic inhibition enhances dynamical stability in the model. This is the first computational approach incorporating anatomical and physiological constraints to formally model brain processes underlying intensive meditation, offering testable hypotheses for attention training and potential clinical applications.
Journal of psychopharmacology (Oxford, England)
April 1, 2016
Matthew W Johnson, Katherine A Maclean, Michael J Caspers et al.
11 citations
After inhaling a high dose of vaporized salvinorin A (18–21 mcg/kg), plasma levels of the compound peak at 2 minutes and then rapidly decline. Higher drug levels are strongly linked to stronger subjective and observer-rated drug effects. Prolactin rises significantly from 5 minutes onward, peaking at 15 minutes, while cortisol increases are inconsistent across participants. Hormonal changes do not closely track drug levels. This work demonstrates a direct relationship between salvinorin A plasma concentrations and drug effects in humans, validating an efficient inhalation method.