Psychiatry and Clinical Neurosciences
June 19, 2019
Kenji Hashimoto
325 citations
Ketamine, particularly its enantiomers (R)-ketamine and (S)-ketamine, shows rapid and sustained antidepressant effects in patients with treatment-resistant major depressive disorder (MDD) or bipolar disorder (BD). While (S)-ketamine (esketamine) was FDA-approved as a nasal spray in 2019 due to its higher affinity for the NMDA receptor, preclinical data suggest (R)-ketamine may have greater potency, longer-lasting effects, and fewer side effects. The author reviews the historical development of ketamine enantiomers and their metabolites, compares other rapid-acting antidepressant candidates, and discusses the molecular and cellular mechanisms underlying ketamine's effects.
Psychiatry and Clinical Neurosciences
December 1, 1966
Akira Kasamatsu, T Hirai
324 citations
During Zen meditation, EEG recordings from 48 Zen priests and disciples showed a consistent pattern of brainwave changes: alpha waves appeared within 50 seconds of starting meditation, their amplitude increased, and their frequency decreased over time. In some priests, rhythmic theta trains emerged. These four EEG stages corresponded to the disciples' mental states, as evaluated by a Zen master, and to their years of training. Unlike drowsiness or hypnotic sleep, the meditation EEG pattern was more persistent and did not shift into deeper sleep. Alpha blocking in response to repeated click stimuli showed no habituation during meditation, whereas control subjects habituated quickly. These findings indicate a specific change of consciousness during Zen meditation.
Psychiatry and Clinical Neurosciences
April 1, 2008
Miho Miyajima, Toshihiko Matsumoto, Shigeo Ito
45 citations
A 40-year-old man with no prior mental illness was brought to an emergency room in a delusional, psychotic state after ingesting a liquid labeled 'Vanilla aroma' to enhance sexual pleasure. The substance contained 2C-T-4, a phenethylamine analog hallucinogen not detected by standard urine screening. He recovered with neuroleptic medication within 17 hours. This is the first reported clinical case of acute psychosis caused by 2C-T-4, which is not legally controlled in many countries including Japan and the USA, and is difficult to detect on routine drug screens.
Psychiatry and Clinical Neurosciences
December 1, 1994
Tetsuhito Murata, Yoshifumi Koshino, Masao Omori et al.
38 citations
During Zen meditation (Zazen), slow alpha brain waves appeared in most subjects regardless of meditation experience, but theta waves appeared only in monks (priests and disciples), predominantly in the frontal region. The frequency of theta waves increased with more years of Zen training. In experienced monks, theta 2–3 (6.0–8.0 Hz) waves increased while the increase in alpha 2 (9.0–10.0 Hz) waves was attenuated over the course of meditation. These EEG changes may reflect a mental state of relaxation combined with heightened consciousness induced by Zazen.
Psychiatry and Clinical Neurosciences
October 1, 2024
Shakila Meshkat, Fatemeh Gholaminezhad, Eric Vermetten et al.
24 citations
A systematic review of 20 studies with 2,959 participants found that psilocybin's effects on cognitive function are mixed. Global cognitive function and processing speed remained mostly unchanged in healthy individuals, while improvements in sustained attention, working memory, and executive function were reported in patients with treatment-resistant depression. Emotional processing and empathy were positively modified, especially in these patients, but cognitive empathy and social cognition were not significantly altered. Cognitive flexibility and creative cognition initially declined but could improve over time. Psilocybin improved semantic associations and associative learning, but effects on episodic and verbal memory were less pronounced than with other cognitive enhancers.
Psychiatry and Clinical Neurosciences
December 1, 2024
Yohei Ohtani, Hideaki Tani, Kie Nomoto-Takahashi et al.
13 citations
In a double-blind randomized placebo-controlled trial with 34 Japanese patients suffering from treatment-resistant depression, intravenous ketamine (0.5 mg/kg) given twice a week for two weeks did not show a statistically significant advantage over placebo in reducing depression scores when all participants were analyzed together. However, among those who completed the full treatment protocol, ketamine led to a significantly greater reduction in depressive symptoms than placebo. Higher baseline depression severity and body mass index were linked to greater symptom improvement with ketamine. Adverse events were more common with ketamine but no serious events occurred. These results suggest ketamine may be effective for treatment-resistant depression across diverse ethnic groups.
Psychiatry and Clinical Neurosciences
April 1, 2024
Ting Xue, Jialing Sheng, Hui Gao et al.
5 citations
An 8-month daily guided intensive meditation-based intervention (iMI) added to a general rehabilitation program reduced persistent hallucinations and delusions and improved health-related quality of life in male inpatients with treatment-refractory schizophrenia. In a randomized trial of 64 participants, those receiving iMI showed significantly greater reductions in Positive and Negative Syndrome Scale total scores, positive symptoms, and hallucination/delusion items at both 3 and 8 months compared with rehabilitation alone. Treatment response rates (at least 25% reduction) for these measures were higher in the iMI group at 8 months. The iMI group also reported better physical activity and mindfulness skills. Longer iMI duration produced stronger benefits.
Psychiatry and Clinical Neurosciences
June 1, 1967
Y Shimazono, Katsumi Ando, Takashi Tanaka et al.
4 citations
In 45 normal subjects, horizontal eye movements changed after psychotropic drugs. Amobarbital and chlorpromazine gradually eliminated rapid eye movements. LSD-25 increased rapid movements in 80% of subjects and produced large, slow pendular movements in about half, especially among those showing euphoria, disinhibition, and ecstasy. Psilocybin caused similar pendular movements but with longer duration. Methamphetamine and epinephrine initially decreased slow movements and increased rapid ones; epinephrine later transiently increased slow movements. The findings suggest different drugs distinctly alter eye movement patterns, possibly reflecting their mechanisms of action.
Psychiatry and Clinical Neurosciences
May 17, 2024
Vanessa Siffredi, Maria Chiara Liverani, Natalia B. Fernandez et al.
2 citations
Adolescents born very preterm (before 32 weeks) showed reduced executive and socioemotional functioning compared to full-term controls. After an 8-week mindfulness-based intervention, their scores on these measures improved significantly. The improvement in executive functioning was linked to reliable changes in the duration of activation of several large-scale brain networks during rest, including frontolimbic, amygdala-hippocampus, dorsolateral prefrontal, and visual networks. These networks are involved in self-regulation, attentional control, and awareness of sensory stimuli.
Psychiatry and Clinical Neurosciences
February 26, 2026
Kengo Yonezawa, M. Hirata, Hiroaki Takano et al.
1 citation
Psilocybin, a classic psychedelic compound, is being reexamined as a treatment for psychiatric disorders after decades of legal restrictions. Clinical trials report therapeutic effects for major depressive disorder, depressive symptoms in life-threatening illnesses, and some substance use disorders, with phase III trials for depression underway. Short-term side effects are generally mild and transient, but long-term effects need investigation. Neuroimaging research, mainly using MRI and EEG, is limited and focused on MDD, though ongoing trials include broader studies. Regulatory frameworks vary; controlled use is permitted in Switzerland, parts of the US, Canada, and Australia. Challenges remain, including the need for larger blinded trials and standardized protocols.
Psychiatry and Clinical Neurosciences
July 15, 2025
Hitoshi Sakurai, Daiki Setoyama, Takahiro A Kato et al.
1 citation
In an open-label study of 30 patients with treatment-resistant depression, four intravenous ketamine infusions (0.5 mg/kg) over two weeks rapidly reduced depression severity: the average Montgomery-Åsberg Depression Rating Scale score fell from 30.6 to 20.3 after the fourth infusion, and 26.7% of participants achieved remission. However, only 13.3% remained in remission at 12 months. Early changes in the metabolite 3-hydroxybutyrate predicted the degree of improvement both after the fourth infusion and at 12 months, suggesting it could serve as a biomarker for treatment response. The findings point toward more individualized use of ketamine infusions.
Psychiatry and Clinical Neurosciences
May 30, 2026
Nathalia Novaretti, Rebeca Mendes P Pessoa, Jaime Eduardo Cecilio Hallak et al.
Oral ketamine shows a favorable short-term safety profile across a range of uses, including depression, chronic pain, and pediatric sedation, based on a systematic review of 18 randomized controlled trials involving adults, children, and healthy volunteers. Adverse effects were predominantly mild and transient; in depression studies (427 participants), effects were mild, and pediatric premedication trials (239 participants) reported transient neurological effects without significant safety concerns. Pain and experimental studies (372 participants) showed mostly mild adverse events, with dissociative symptoms at higher doses. Dizziness, sedation, and dissociation were more common with ketamine, while serious adverse events were rare. However, the certainty of evidence is low, and long-term safety remains uncertain.
Psychiatry and Clinical Neurosciences
May 7, 2026
Abidemi Otaiku
Frequent disturbing dreams (bad dreams or nightmares occurring at least weekly) are linked to a higher risk of developing dementia and Alzheimer's disease in later life, according to a longitudinal multi-cohort study of 10,238 adults aged 60 to 89 from six countries across Asia, South America, and Europe, followed for an average of 6.5 years. The relationship was stronger in men than in women, and the finding that disturbing dreams may predict Alzheimer's disease is novel, as prior research focused on Lewy body dementia. However, differences in how disturbing dreams and dementia were measured across cohorts mean these sex- and disease-specific patterns need replication with harmonized methods.
Psychiatry and Clinical Neurosciences
April 18, 2023
Lucy Chester, L. Valmaggia, M. Kempton et al.
Cannabis use is associated with an increased risk of developing psychotic disorders among people already at clinical high risk for psychosis. In a prospective study of this population, cannabis use was linked to a higher incidence of psychotic disorders and to more persistent psychotic symptoms, as well as poorer functional outcomes. The findings strengthen evidence that cannabis acts as a risk factor for psychosis, though the direction of causality remains debated.
Psychiatry and Clinical Neurosciences
November 27, 2019
Akira Ninomiya, Mitsuhiro Sado, Sunre Park et al.
Mindfulness-based cognitive therapy (MBCT) helped reduce depression in patients who had not recovered despite prior medication. In a secondary-care setting, patients who received MBCT showed significantly greater improvement in depressive symptoms compared to those receiving treatment as usual. The therapy was especially beneficial for those with more severe or chronic depression. The findings suggest MBCT can be an effective additional treatment for people who have not responded to pharmacotherapy alone.
Psychiatry and Clinical Neurosciences
December 1, 2016
Chanchan Shen, Jiawei Wang, Guorong Ma et al.
People with nightmare disorder show altered resting-state brain activity compared to healthy volunteers. Fifteen nightmare disorder patients and 15 healthy controls completed questionnaires and resting-state fMRI scans. Patients scored higher on measures of physical effect and horrible stimulation from nightmares. They had higher regional homogeneity (a measure of local brain connectivity) in the left anterior cingulate cortex and right inferior parietal lobule, and lower regional homogeneity in the left superior and inferior frontal gyri and bilateral middle occipital gyri.
Psychiatry and Clinical Neurosciences
August 1, 2009
Alejandro Jiménez-Genchi, Víctor M Avila-Rodríguez, Frida Sánchez-Rojas et al.
Sleep paralysis, known colloquially in Mexico as 'a dead body climbed on top of me,' is a common experience among adolescents. In a survey of 322 Mexican high school students, 92.5% had heard the folk expression and 27.6% had experienced the phenomenon. The prevalence of sleep paralysis was 25.5%, with 22% reporting hypnagogic or hypnopompic hallucinations. Most (61%) had two or more lifetime episodes, with an average onset age of 12.5 years. Episodes typically included both paralysis and hallucinations (72%), while 20.2% involved only paralysis and 7.8% only hallucinations. Sleepiness scores did not differ between those who had experienced sleep paralysis and those who had not.
Psychiatry and Clinical Neurosciences
June 1, 2009
Miyuki Sugiura, Masataka Hirosawa, Sumio Tanaka et al.
A Japanese version of the Cambridge Depersonalization Scale (J-CDS) showed good reliability and validity for screening depersonalization disorder in non-clinical settings. Cronbach's alpha was 0.94 and split-half reliability was 0.93. Scores on the J-CDS were significantly higher in the depersonalization group than in healthy controls and correlated with scores on the Dissociative Experience Scale and its depersonalization subscale. A cut-off score of 60 yielded a sensitivity of 1.00 and specificity of 0.96 for distinguishing individuals with depersonalization disorder from those without psychiatric disorders.
Psychiatry and Clinical Neurosciences
February 1, 2008
Umit B Semiz, Cengiz Basoglu, Servet Ebrinc et al.
Borderline personality disorder (BPD) patients experience significantly more nightmares, higher dream anxiety, and worse subjective sleep quality than healthy controls. Among BPD patients, greater dream anxiety is linked to more childhood trauma, dissociative symptoms, and impaired sleep. Those with nightmare disorder show a more severe clinical profile. The findings suggest that addressing dream and sleep disturbances in BPD could improve overall clinical outcomes.
Psychiatry and Clinical Neurosciences
December 1, 2003
Mehmet Yucel Agargun, Hayrettin Kara, Ömer Akil Özer et al.
Among 30 patients with dissociative disorders, 57% also met criteria for nightmare disorder. Those with both conditions were more likely to engage in self-mutilative behavior, have attempted suicide in the past year, and have a comorbid diagnosis of borderline personality disorder compared to dissociative patients without nightmares. The findings suggest that nightmares and dreams warrant attention in the treatment of dissociative disorders.
Psychiatry and Clinical Neurosciences
April 1, 1998
Hideki Tanaka, Mitsuo Hayashi, Tadao Hori
Hypnagogic EEG stages, defined by Hori's nine-stage system, show distinct topographic patterns of brain activity as sleep progresses. Delta and theta power increase prominently in anterior-central areas starting from the vertex sharp-wave stage (stages 6 and 7). Alpha 3 power increases in anterior-central areas from stage 9, and sigma power increases in the central-parietal area from stage 8. These findings suggest that basic sleep processes may begin before the onset of sleep stage 2 or before manually scored sleep spindles appear.
Psychiatry and Clinical Neurosciences
April 1, 1998
K Takata, Y Inoue, H Hazama et al.
Three patients reported hypnopompic visual hallucinations at night, resembling Charles Bonnet syndrome. The content of the hallucinations appeared to be attempts at wish fulfillment. In two cases, polysomnograms showed abnormal REM sleep findings during the hallucinations. The authors suggest that dysfunction of the REM sleep mechanism may contribute to these nighttime visual hallucinations, and that the visual experiences might reflect dream content.