Action sequence learning, habits, and automaticity in obsessive-compulsive disorder.

This study investigates the goal/habit imbalance theory of compulsion in obsessive-compulsive disorder (OCD), which postulates enhanced habit formation, increased automaticity, and impaired goal/habit arbitration. It directly tests these hypotheses using newly developed behavioral tasks. First, OCD patients and healthy participants were trained daily for a month using a smartphone app to perform chunked action sequences. Despite similar procedural learning and attainment of habitual performance (measured by an objective automaticity criterion) by both groups, OCD patients self-reported higher subjective habitual tendencies via a recently developed questionnaire. Subsequently, in a re-evaluation task assessing choices between established automatic and novel goal-directed actions, both groups were sensitive to re-evaluation based on monetary feedback. However, OCD patients, especially those with higher compulsive symptoms and habitual tendencies, showed a clear preference for trained/habitual sequences when choices were based on physical effort, possibly due to their higher attributed intrinsic value. These patients also used the habit-training app more extensively and reported symptom relief post-study. The tendency to attribute higher intrinsic value to familiar actions may be a potential mechanism leading to compulsions and an important addition to the goal/habit imbalance hypothesis in OCD. We also highlight the potential of smartphone app training as a habit reversal therapeutic tool.

ØCD: protocol for the development and evaluation of a cognitive-behavioral prevention program for obsessive-compulsive disorder.

BACKGROUND: Obsessive-compulsive disorder (OCD) imposes significant burdens on individuals, families, and healthcare systems and the COVID-19 pandemic appears to have exacerbated OCD symptoms. Currently, there are no validated prevention programs for OCD, highlighting a critical gap in mental health services. This study aims to develop and validate the first ØCD prevention program, for at-risk adults, utilizing cognitive-behavioral therapy (CBT) and exposure response prevention (ERP) techniques. METHODS: A single-blind, randomized controlled trial comparing the ØCD prevention program to a waitlist control group will be conducted. Participants, at-risk adults (18-65 years) with subclinical OCD symptoms (OCI-R score ≥ 12), will be recruited for the study. The ØCD prevention program compresise of six online group sessions incorporating CBT and ERP techniques over three modules. The primary outcomes are OCD symptom severity (measured by the Obsessive-Compulsive Inventory- revised form; OCI-R), depression symptoms (measured by the Patient Health Questionnaire; PHQ-9), and anxiety symptoms (measured by the Generalised Anxiety Disorder 7-item; GAD-7). Secondary outcomes include OCD-related beliefs, experiential avoidance, resilience, quality of life, uncertainty intolerance, automatic thoughts, and distress. Outcome measures will be collected at baseline, at completion of the intervention, and one year later (follow-up). At follow-up, we will also analyze the OCD diagnostic incidence, using the Structured Clinical Interview for DSM-5. We will employ a multivariate analysis of variance (MANOVA) to explore whether significant differences exist between groups across dependent variables. To compare the OCD incidence levels from the pre-test to the follow-up we will use the chi-squared test. DISCUSION: The present study may contribute novel data on the efficacy of OCD prevention approaches, leading to the development of an evidence-based OCD prevention program that could alleviate individual and societal burdens associated with OCD. TRIAL REGISTRATION: This trial was approved by the University Ethical Review Authority (937/ 28.11.2023) at Babeș-Bolyai University and is registered on clinicaltrials.gov (ID: NCT06262464).

Altered neural anticipation of reward and loss but not receipt in adolescents with obsessive-compulsive disorder.

BACKGROUND: Obsessive-compulsive disorder (OCD) is characterized by persistent, unwanted thoughts and repetitive actions. Such repetitive thoughts and/or behaviors may be reinforced either by reducing anxiety or by avoiding a potential threat or harm, and thus may be rewarding to the individual. The possible involvement of the reward system in the symptomatology of OCD is supported by studies showing altered reward processing in reward-related regions, such as the ventral striatum (VS) and the orbitofrontal cortex (OFC), in adults with OCD. However, it is not clear whether this also applies to adolescents with OCD. METHODS: Using functional magnetic resonance imaging, two sessions were conducted focusing on the anticipation and receipt of monetary reward (1) or loss (2), each contrasted to a verbal (control) condition. In each session, adolescents with OCD (n1=31/n2=26) were compared with typically developing (TD) controls (n1=33/ n2=31), all aged 10-19 years, during the anticipation and feedback phase of an adapted Monetary Incentive Delay task. RESULTS: Data revealed a hyperactivation of the VS, but not the OFC, when anticipating both monetary reward and loss in the OCD compared to the TD group. CONCLUSIONS: These findings suggest that aberrant neural reward and loss processing in OCD is associated with greater motivation to gain or maintain a reward but not with the actual receipt. The greater degree of reward 'wanting' may contribute to adolescents with OCD repeating certain actions more and more frequently, which then become habits (i.e., OCD symptomatology).

Retinal Tear Following Low-Frequency Repetitive Transcranial Magnetic Stimulation for Obsessive-Compulsive Disorder.

OBJECTIVES: Repetitive transcranial magnetic stimulation (rTMS) is a noninvasive form of brain stimulation that uses magnetic pulses to stimulate specific brain regions. Retina is being investigated whether the retina, which is also known as the brain's window to the outside world, is affected by the treatment. METHODS: Magventure X100 device was used for the procedure. The bilateral supplementary motor area was targeted. Procedure protocol: power: 47%, repetitive rate (frequency): 1 Hz, pulses in train duration: 300, intertrain interval (waiting time): 120 seconds, number of trains: 4, total pulses: 1200. Twenty sessions of rTMS were planned for the patient. The patient was informed about the procedure, and her consent was obtained. RESULTS: The Yale-Brown Obsessive-Compulsive Disorder Scale (YBOCS) score before the first session was 31, and the Brown Assessment Beliefs Scale (BABS) score was 5. The patient's YBOCS score after the 15th session was 14, and the BABS score was 0. After the implementation of the 15th session of the patient's treatment, retinal detachment developed in the right eye, and the treatment was terminated. As a result of the eye examination of the patient, it was determined that there was 1 horseshoe rupture and 2 hole-shaped ruptures in the lower half of the left eye. CONCLUSIONS: Patients at risk for retinal detachment may require specialized treatment and close monitoring to prevent the condition from worsening. It is important to consult with an ophthalmologist for patients at risk for retinal detachment before TMS application.

The relationship between obsessive-compulsive symptoms and real-life functioning in schizophrenia: New insights from the multicenter study of the Italian Network for Research on Psychoses.

BACKGROUND: Although obsessive-compulsive disorder (OCD) is highly prevalent in schizophrenia, its relationship with patients' real-life functioning is still controversial. METHODS: The present study aims at investigating the prevalence of OCD in a large cohort of non-preselected schizophrenia patients living in the community and verifying the relationship of OCD, as well as of other psychopathological symptoms, with real-life functioning along a continuum of OCD severity and after controlling for demographic variables. RESULTS: A sample of 327 outpatients with schizophrenia was enrolled in the study and collapsed into three subgroups according to OCD severity (subclinical, mild-moderate, severe). A series of structural equation modeling (SEM) was performed to analyze in each subgroup the association of obsessive-compulsive symptoms with real-life functioning, assessed through the Specific Levels of Functioning Scale and the UCSD Performance-Based Skills Assessment. Moreover, latent profile analysis (LPA) was performed to infer latent subpopulations. In the subclinical OCD group, obsessive-compulsive symptoms (OCS) were not associated with functioning, whereas in the mild-moderate OCD group, they showed a positive relationship, particularly in the domains of work and everyday life skills. The paucity of patients with severe OCD did not allow performing SEM analysis in this group. Finally, LPA confirmed a subgroup with mild-moderate OCS and more preserved levels of functioning. CONCLUSIONS: These findings hint at a positive association between mild-moderate OCD and real-life functioning in individuals with schizophrenia and encourage a careful assessment of OCD in personalized programs to sustain daily life activities.

Neurosurgical neuromodulation therapy for psychiatric disorders.

Psychiatric disorders are among the leading contributors to global disease burden and disability. A significant portion of patients with psychiatric disorders remain treatment-refractory to best available therapy. With insights from the neurocircuitry of psychiatric disorders and extensive experience of neuromodulation with deep brain stimulation (DBS) in movement disorders, DBS is increasingly being considered to modulate the neural network in psychiatric disorders. Currently, obsessive-compulsive disorder (OCD) is the only U.S. FDA (United States Food and Drug Administration) approved DBS indication for psychiatric disorders. Medically refractory depression, addiction, and other psychiatric disorders are being explored for DBS neuromodulation. Studies evaluating DBS for psychiatric disorders are promising but lack larger, controlled studies. This paper presents a brief review and the current state of DBS and other neurosurgical neuromodulation therapies for OCD and other psychiatric disorders. We also present a brief review of MR-guided Focused Ultrasound (MRgFUS), a novel form of neurosurgical neuromodulation, which can target deep subcortical structures similar to DBS, but in a noninvasive fashion. Early experiences of neurosurgical neuromodulation therapies, including MRgFUS neuromodulation are encouraging in psychiatric disorders; however, they remain investigational. Currently, DBS and VNS are the only FDA approved neurosurgical neuromodulation options in properly selected cases of OCD and depression, respectively.

Does mental contamination mediate the association between childhood trauma and obsessive-compulsive symptoms in adults?

BACKGROUND: Previous research has shown that individuals with obsessive-compulsive disorder (OCD) and OCD symptoms have higher rates of childhood trauma. Although it has been suggested that this relationship is due to mental contamination that developed in response to trauma, no studies have investigated the associations between childhood trauma, mental contamination, and OCD, and none have examined whether the relationship between childhood trauma and OCD is mediated by mental contamination. OBJECTIVE: We hypothesized that OCD, childhood trauma, and mental contamination are positively correlated, and that mental contamination would mediate the association between childhood trauma and OCD symptoms PARTICIPANTS AND SETTING: We tested these hypotheses in a sample of 245 individuals, which comprised 158 MTurk workers recruited via CloudResearch.com and 87 individuals recruited through social media with OCD diagnoses or OCD symptoms above the clinical cutoff on the Obsessive-Compulsive Inventory-Revised. METHODS: Participants completed online self-report questionnaires on childhood trauma, mental contamination, and OCD symptoms. RESULTS: The results revealed statistically significant positive correlations between childhood trauma, mental contamination, and OCD, and statistically significant total and indirect effects for the simple mediational model. Exploratory re-analyses with participants who had high OCD symptoms (n = 87) showed similar results. CONCLUSIONS: Our research shows that the association between childhood trauma and OCD may be explained by mental contamination. We recommend that mental contamination should be assessed and addressed in OCD patients with a history of childhood trauma.

From compulsivity to compulsion: the neural basis of compulsive disorders.

Compulsive behaviour, an apparently irrational perseveration in often maladaptive acts, is a potential transdiagnostic symptom of several neuropsychiatric disorders, including obsessive-compulsive disorder and addiction, and may reflect the severe manifestation of a dimensional trait termed compulsivity. In this Review, we examine the psychological basis of compulsions and compulsivity and their underlying neural circuitry using evidence from human neuroimaging and animal models. Several main elements of this circuitry are identified, focused on fronto-striatal systems implicated in goal-directed behaviour and habits. These systems include the orbitofrontal, prefrontal, anterior cingulate and insular cortices and their connections with the basal ganglia as well as sensoriomotor and parietal cortices and cerebellum. We also consider the implications for future classification of impulsive-compulsive disorders and their treatment.

The role of psychosis and clozapine load in excessive checking in treatment-resistant schizophrenia: longitudinal observational study.

BACKGROUND: A significant proportion of people with clozapine-treated schizophrenia develop 'checking' compulsions, a phenomenon yet to be understood. AIMS: To use habit formation models developed in cognitive neuroscience to investigate the dynamic interplay between psychosis, clozapine dose and obsessive-compulsive symptoms (OCS). METHOD: Using the anonymised electronic records of a cohort of clozapine-treated patients, including longitudinal assessments of OCS and psychosis, we performed longitudinal multi-level mediation and multi-level moderation analyses to explore associations of psychosis with obsessiveness and excessive checking. Classic bivariate correlation tests were used to assess clozapine load and checking compulsions. The influence of specific genetic variants was tested in a subsample. RESULTS: A total of 196 clozapine-treated individuals and 459 face-to-face assessments were included. We found significant OCS to be common (37.9%), with checking being the most prevalent symptom. In mediation models, psychosis severity mediated checking behaviour indirectly by inducing obsessions (r = 0.07, 95% CI 0.04-0.09; P < 0.001). No direct effect of psychosis on checking was identified (r = -0.28, 95% CI -0.09 to 0.03; P = 0.340). After psychosis remission (n = 65), checking compulsions correlated with both clozapine plasma levels (r = 0.35; P = 0.004) and dose (r = 0.38; P = 0.002). None of the glutamatergic and serotonergic genetic variants were found to moderate the effect of psychosis on obsession and compulsion (SLC6A4, SLC1A1 and HTR2C) survived the multiple comparisons correction. CONCLUSIONS: We elucidated different phases of the complex interplay of psychosis and compulsions, which may inform clinicians' therapeutic decisions.

Crocin (bioactive compound of Crocus sativus L.) potently restores REM sleep deprivation-induced manic- and obsessive-compulsive-like behaviors in female rats.

Rapid-eye movement (REM) sleep deprivation (SD) can induce manic-like behaviors including hyperlocomotion. On the other hand, crocin (one of the main compounds of Crocus sativus L. or Saffron) may be beneficial in the improvement of mental and cognitive dysfunctions. Also, crocin can restore the deleterious effects of SD on mental and cognitive processes. In this study, we investigated the effect of REM SD on female rats' behaviors including depression- and anxiety-like behaviors, locomotion, pain perception, and obsessive-compulsive-like behavior, and also, the potential effect of crocin on REM SD effects. We used female rats because evidence on the role of REM SD in modulating psychological and behavioral functions of female (but not male) rats is limited. REM SD was induced for 14 days (6h/day), and crocin (25, 50, and 75 mg/kg) was injected intraperitoneally. Open field test, forced swim test, hot plate test, and marble burying test were used to assess rats' behaviors. The results showed REM SD-induced manic-like behavior (hyperlocomotion). Also, REM SD rats showed decreased anxiety- and depression-like behavior, pain subthreshold (the duration it takes for the rat to feel pain), and showed obsessive compulsive-like behavior. However, crocin at all doses partially or fully reversed REM SD-induced behavioral changes. In conclusion, our results suggested the possible comorbidity of OCD and REM SD-induced manic-like behavior in female rats or the potential role of REM SD in the etiology of OCD, although more studies are needed. In contrast, crocin can be a possible therapeutic choice for decreasing manic-like behaviors.

Family accommodation in obsessive-compulsive disorder: An updated systematic review and meta-analysis.

Family accommodation might play a crucial role in obsessive-compulsive disorder (OCD). Previous systematic reviews on family accommodation in OCD have focused on specific populations or variables or are outdated. We conducted a preregistered systematic review and meta-analysis on family accommodation in adults, children, and adolescents with OCD (CRD42021264461). We searched PubMed, Scopus, and Web of Science using the keywords "family accommodation" and "obsessive-compulsive disorder. One hundred-eight studies involving 8928 individuals with OCD were included. Our results indicate that levels of family accommodation in OCD are moderate, that there is a significant positive correlation between family accommodation and OCD severity (r = 0.42), that baseline family accommodation does not predict pre- to post-treatment change in OCD severity (g = -0.03), and that family accommodation decreases as a result of both individual and family-focused cognitive behavioral therapy for OCD (g = 2.00 and g = 1.17, respectively). Our findings highlight the relevance of family accommodation in OCD and may help guide assessment and treatment.

Mechanisms of therapeutic change after psychedelic treatment in OCD.

Novel treatments are required for the 30-50% of individuals with obsessive-compulsive disorder (OCD) who remain resistant to first-line pharmacological and psychotherapeutic treatments. Recent pilot data suggest benefit from psilocybin-assisted psychotherapy (PAP) and from imagery rescripting (ImRs). We explore psychological mechanisms of change underpinning both interventions that appear to allow for reprocessing of negative emotions and core beliefs associated with past aversive events. A next critical step in PAP is the development of psychotherapeutic frameworks grounded in theory. We propose that basing PAP on an ImRs framework may provide synergistic benefits in symptom reduction, modification of core beliefs, and value-based living.

The anxiety response of patients with severe psychiatric disorders to the recent public health crisis.

BACKGROUND: The devastating health, economic, and social consequences of COVID-19 may harm the already vulnerable groups, particularly people with severe psychiatric disorders (SPDs). The present study was conducted to investigate the anxiety response of patients with SPDs during the COVID-19 pandemic. METHODS: A total of 351 patients with SPDs [Schizophrenia Spectrum (SSD), Bipolar (BD), Major Depressive (MDD), and Obsessive-Compulsive (OCD) Disorders] and healthy controls in Guilan province, Iran, throughout 2021-2022 were included in this cross-sectional analytical study. The anxiety response consisted of four concepts: COVID-19-related anxiety, general health anxiety, anxiety sensitivity, and safety behaviors. We conducted an unstructured interview and provided sociodemographic and clinical information. Also, the participants were asked to complete four self-report measures of the Corona Disease Anxiety Scale, the Anxiety Sensitivity Index-Revised, the Short Health Anxiety Inventory, and the Checklist of Safety Behaviors. RESULTS: Analysis of variance showed a significant difference between the groups of patients with SPDs and the control group in COVID-19-related anxiety (F = 6.92, p = 0.0001), health anxiety (F = 6.21, p = 0.0001), and safety behaviors (F = 2.52, p = 0.41). No significant difference was observed between them in anxiety sensitivity (F = 1.77, p = 0.134). The Games-Howell test showed that the control group obtained a higher mean than the groups of people with BD (p < 0.0001), SSD (p = 0.033), and OCD (p = 0.003) disorders in COVID-19-related anxiety. The patients with MDD (p = 0.014) and OCD (p = 0.01) had a higher mean score than the control group in health anxiety. Tukey's test showed that the mean of safety behaviors of the control group was significantly higher than the OCD group (p = 0.21). No significant difference was found between the groups of patients with MDD, BD, SSD, and OCD in terms of COVID-19-related anxiety, health anxiety, and safety behaviors. CONCLUSION: Anxiety response to health crisis is different in groups with SPDs and control group. The findings of this study suggest that although health anxiety is present in many of these patients during the pandemic, their anxiety response to the health crisis may be less than expected. There can be various explanations, such as pre-existing symptoms, low health literacy, and possible co-occurring cognitive impairment. The results of this study have many practical and policy implications in meeting the treatment needs of this group of patients during public health crises and indicate that their needs may not be compatible with the expectations and estimates that health professionals and policymakers already have.

Implementation and Preliminary Outcomes of an Exposure-Based Summer Camp for Pediatric OCD and Anxiety.

Despite the high prevalence of anxiety disorders in children and adolescents and the existence of effective evidence-based treatments for them, access to psychological care remains a major public health concern. Summer camps may provide an effective treatment avenue for youth who might not otherwise have access to care. This study describes the design and implementation of Fear Facers, a semistructured, 5-day, daytime exposure-therapy-based summer camp designed for youth with a primary diagnosis of obsessive-compulsive disorder (OCD), social anxiety, separation anxiety, or a specific phobia. Preliminary data regarding feasibility and patient outcomes is also reported. Among 52 children and adolescents aged 7 to 16 who attended one of six camp sessions between 2018 and 2021, significant reductions in anxiety (d = 0.54) and OCD symptoms (d = 0.57) were observed from pre-camp to immediately post-camp. A subset of campers who were followed for an additional 3 months post-camp (n = 22) showed maintenance of treatment gains. Retention rates for the intervention were high. Our investigation provides further support for the use of a camp-based design for cognitive-behavioral approaches, and may provide a unique setting to maximize elements of inhibitory learning in exposures. We also discuss a number of elements regarding feasibility that need consideration for those hoping to develop similar interventions.

Identification of key mRNAs and signaling pathways in obsessive compulsive disorder based on weighted gene co-expression network analysis and cytoHubba plugin.

PURPOSE: Obsessive-compulsive disorder (OCD) is a complex psychiatric disorder. Genetic and broad environmental factors are common risk factors for OCD. The purpose of this study is to explore the molecular mechanism of OCD and to find new molecular targets for the diagnosis and management of OCD. METHODS: All data were downloaded from public dataset. Key modules and candidate key mRNAs were identified based on weighted gene co-expression network analysis (WGCNA). The "limma" R package was used for differential expression analysis of mRNAs. Subsequently, functional enrichment analysis of differentially expressed mRNAs (DEmRNAs) was also carried out. In addition, a diagnostic model was constructed. Finally, the infiltration level of immune cells in OCD and its correlation with multicentric key DEmRNAs were analyzed. RESULTS: Green and red modules were selected as the hub modules. A total of 447 mRNAs were considered candidate key mRNAs according to GS > 0.2 and MM > 0.3. A total of 26 DEmRNAs in the same direction were identified in the GSE60190 and GSE78104 datasets. A total of 26 DEmRNAs were intersected with candidate key mRNAs in WGCNA to obtain 10 intersection DEmRNAs (HSPB1, ITPK1, CBX7, PPP1R10, TAOK1, PISD, MKNK2, RWDD1, PPA1, and RELN). However, only four DEmRNAs (HSPB1, TAOK1, MKNK2, and PPA1) predicted related drugs. Subsequently, receiver operating characteristic analysis shows that the diagnostic model has high diagnostic value. Moreover, six multicentric key DEmRNAs (SNRPF, SNRNP70, PRPF8, NOP56, EPRS, and CCT2) were screened by UpSet package. Finally, six multicentric key DEmRNAs were found to be associated with immune cells. CONCLUSION: The key molecules obtained in this study lay a foundation for further research on the molecular mechanism of OCD.

The COGINS: A New Measure of Cognitive Insight in Obsessive-Compulsive and Related Disorders.

Research suggests that individuals with obsessive-compulsive and related disorders (OCRDs) with lower insight show a poorer response to cognitive behavioral therapy and might benefit from alternative treatments. However, there are inconsistencies in the literature regarding the definition and measurement of insight. This study endeavored to evaluate the psychometric properties of the Cognitive Obsessional Insight Scale (COGINS), a novel self-report measure of cognitive insight in OCRDs. The sample comprised 166 participants with a diagnosis of obsessive-compulsive disorder or body dysmorphic disorder enrolled in clinical trials. Participants completed the COGINS and a questionnaire battery at baseline and posttreatment. The COGINS demonstrated good internal consistency, test-rest reliability, convergent validity with other OCRD-specific measures of insight, positive associations with OCRD symptomatology, and had a moderating effect on treatment response. The COGINS is a valid and reliable practical tool to measure cognitive insight in OCRDs and might help toward clarifying the role of cognitive insight in this population.

Resting-state functional connectivity of amygdala subregions predicts treatment outcome for cognitive behavioral therapy in obsessive-compulsive disorder at a 4-month follow-up.

BACKGROUND: Cognitive behavioral therapy (CBT) is considered as the first-line treatment for obsessive-compulsive disorder (OCD). However, the underlying neural mechanisms through which CBT exerts its effects in OCD remain unclear. This study aims to investigate whether the improvement of clinical symptoms in OCD patients after CBT treatment is associated with changes in resting-state functional connectivity (FC) of the amygdala subregion, and whether these changes can be served as potential predictors of four-months treatment efficacy. METHODS: We collected resting-state functional magnetic resonance imaging (rs-fMRI) data from 57 OCD patients and 50 healthy subjects at baseline. In the patient group, rs-fMRI was also obtained after completion of an 8-week CBT treatment and 4 months post-treatment. A whole-brain rsFC analysis was conducted using the amygdala subregion as the seed point. We analyzed the FC patterns in relation to 4 months clinical outcomes to elucidate the long-term efficacy of CBT in OCD patients. RESULTS: Treatment responseat at pre-treatment was found to be associated with reduced rsFC between the left basolateral amygdala(BLA)and left superior temporal gyrus(STG) at baseline. Lower pre-treatment FC were negatively correlated with the severity of OCD symptoms as measured by the Yale-Brown Obsessive Compulsive Severity Scale (Y-BOCS). Moreover, the area under the receiver operating characteristic (ROC) curve for the FC between the left BLA and STG at the end of treatment was 73.0% and 70.4% for the effective-ineffective and remitted or unremitted groups, respectively. At the 4-month follow-up, the area under the ROC curve for the effective-ineffective and remitted or unremitted groups was 83.9% and 76.5%, respectively. CONCLUSION: These findings suggest that brain functional activity in patients with OCD can predict treatment response to CBT, and longitudinal changes in relevant brain functional activity following CBT treatment are associated with treatment response in OCD.

Efficacy and safety of psychedelics for the treatment of mental disorders: A systematic review and meta-analysis.

We aim to systematically review and meta-analyze the effectiveness and safety of psychedelics [psilocybin, ayahuasca (active component DMT), LSD and MDMA] in treating symptoms of various mental disorders. Web of Science, Embase, EBSCO, and PubMed were searched up to February 2024 and 126 articles were finally included. Results showed that psilocybin has the largest number of articles on treating mood disorders (N = 28), followed by ayahuasca (N = 7) and LSD (N = 6). Overall, psychedelics have therapeutic effects on mental disorders such as depression and anxiety. Specifically, psilocybin (Hedges' g = -1.49, 95% CI [-1.67, -1.30]) showed the strongest therapeutic effect among four psychedelics, followed by ayahuasca (Hedges' g = -1.34, 95% CI [-1.86, -0.82]), MDMA (Hedges' g = -0.83, 95% CI [-1.33, -0.32]), and LSD (Hedges' g = -0.65, 95% CI [-1.03, -0.27]). A small amount of evidence also supports psychedelics improving tobacco addiction, eating disorders, sleep disorders, borderline personality disorder, obsessive-compulsive disorder, and body dysmorphic disorder. The most common adverse event with psychedelics was headache. Nearly a third of the articles reported that no participants reported lasting adverse effects. Our analyses suggest that psychedelics reduce negative mood, and have potential efficacy in other mental disorders, such as substance-use disorders and PTSD.