The Psychedelic Renaissance in Clinical Research: A Bibliometric Analysis of Three Decades of Human Studies with Psychedelics

Psychedelics were used in the treatment of psychiatric conditions prior to their prohibition in the late 1960s. In the past three decades, there is a revived research interest in the therapeutic potential of psychedelic drugs with expected FDA approvals for treatment of various conditions. Given the exponential scientific growth of this field, we sought to characterize, analyze, and visualize trends in its top-cited articles. Bibliometric analyses are quantitative approaches to characterize a scientific field, including evaluation of the impact of academic literature. The bibliometric analysis and visualizations were conducted with R-tools for comprehensive science mapping. The top-cited 100 articles were cited between 82 and 668 times (median 125; mean 158). Fifty-four percent of the T100 articles were produced in the past decade (2010-2020). Network and author impact analysis highlighted key figures and primary collaboration networks within the top 100 publications. UK, USA, Switzerland, Spain, and Brazil lead the field. Results are discussed in terms of research growth, access, diversity, and the distribution of knowledge and experience in the field. These aggregated data and insights on the second wave of psychedelic research facilitate research evaluation, data-driven funding policies, and a practical map for researchers and clinicians entering the field.

A supervised machine learning model for imputing missing boarding stops in smart card data

Public transport has become an essential part of urban existence with increased population densities and environmental awareness. Large quantities of data are currently generated, allowing for more robust methods to understand travel behavior by harvesting smart card usage. However, public transport datasets suffer from data integrity problems; boarding stop information may be missing due to imperfect acquirement processes or inadequate reporting. This study introduces a supervised machine learning method to impute missing boarding stops based on ordinal classification using GTFS timetable, smart card, and geospatial datasets. A new metric, Pareto Accuracy, is suggested to evaluate algorithms where classes have an ordinal nature. The results are based on a case study in the city of Beer Sheva, Israel, consisting of one month of smart card data. We show that our proposed method is robust to irregular travelers and significantly outperforms well-known imputation methods without the need to mine any additional datasets. The data validation from another Israeli city using transfer learning shows the presented model is general and context-free. The implications for transportation planning and travel behavior research are further discussed.

The association between cannabis use and psychiatric comorbidity in people with personality disorders: A population-based longitudinal study

Both personality disorders (PD) and cannabis use are highly comorbid with various psychiatric disorders. While previous research indicates specific interactions between cannabis use and schizotypal PD associated with schizophrenia, research into cannabis use among individuals with other PDs and the development of several additional psychiatric disorders is scarce. We explored the prevalence and incidence of psychiatric disorders among individuals with PDs who use cannabis, and whether individuals with PDs who use cannabis are at increased risk for developing psychiatric disorders compared to cannabis users without a PD. Finally, we examined the interaction effect between cannabis use and personality disorders on comorbid psychiatric disorders. Data from 34,653 participants in waves 1 and 2 of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) were analyzed. Our findings indicate that individuals with PDs who used cannabis were at increased odds for developing substance use disorders (including opioid use disorder), but not other comorbid psychiatric disorders, at 3-year follow up. No significant interaction effects were generally found between cannabis use and PD. These findings suggest that aside from specific substance use disorders, individuals with PDs are not at an increased risk for developing other psychiatric disorders following cannabis use.

The association between cannabis use and suicidality among men and women: A population-based longitudinal study

BACKGROUND

Evidence regarding the role of sex differences in the association between cannabis use and suicidality is lacking. We explored sex differences in the bidirectional association between cannabis use and suicidality in a 3-year longitudinal study.

METHODS

Data were drawn from waves 1 and 2 of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). Bidirectional analyses were conducted separately by sex, exploring incidence of suicidality among cannabis users (n=963 vs. 30,586 non-users) as well as initiation of cannabis use among suicidal individuals (n=1805 vs. 25,729 non-suicidal). Cannabis use was categorized based on frequency of use. Multivariate logistic regression analyses controlling for multiple covariates were conducted.

RESULTS

Cannabis use was significantly associated with increased incidence of suicidality among men (Adjusted Odds Ratio [AOR] for any cannabis use =1.91[1.02-3.56]) but not among women (AOR=1.19[0.64-2.20]). Daily cannabis use was significantly associated with increased incidence of suicidality among men (AOR=4.28[1.32-13.82]) but not among women (AOR=0.75[0.28-2.05]). Conversely, baseline suicidality was associated with initiation of cannabis use among women (AOR=2.34[1.42-3.87]) but not among men (AOR=1.10[0.57-2.15]). Separate analyses of suicidal ideation and suicide attempts demonstrated a significant association between cannabis use and subsequent incidence of suicidal ideation in men, and a significant association between baseline suicidal ideation and subsequent initiation of cannabis use in women. No significant association was found for the bidirectional association between cannabis use and suicide attempts in either sex.

LIMITATIONS

Suicidality was assessed only in individuals reporting depressed mood and/or anhedonia.

CONCLUSIONS

Our findings support a longitudinal association between heavy cannabis use and the incidence of suicidality in men, but not in women. Conversely, baseline suicidality is longitudinally associated with the initiation of cannabis use in women, but not in men. This may have implications on clinical and social aspects of cannabis use and merit further research into the unique effects of sex differences on cannabis induced psychopathology.

Characteristics of Synthetic Cannabinoid and Cannabis Users Admitted to a Psychiatric Hospital: A Comparative Study

BACKGROUND

Psychotic and affective exacerbations associated with synthetic cannabinoid (SC) use are becoming an emerging concern in psychiatric hospitals. However, data are lacking regarding whether clinical manifestations of SC use differ from those associated with cannabis use.

OBJECTIVE

Our aim was to explore the unique profile of SC users admitted to a mental health center in terms of demographic, clinical, and physiologic variables in comparison to cannabis users.

METHODS

We retrieved retrospective data of patients admitted to a mental health center between October 2007 and May 2014 who self-reported recent use of SC (n = 60) and patients who were cannabis users (positive carboxy-tetrahydrocannabinol urine test at admission) without a history of SC use (n = 163). Clinical measures included hospitalization length, number of previous hospitalizations, Positive and Negative Syndrome Scale (PANSS) scores, psychiatric status at admission, and relevant physiologic and laboratory parameters.

RESULTS

Hospitalized SC users were younger than hospitalized cannabis users (n = 163) (30.46 ± 7.83 years versus 34.67 ± 10.07 years, U₂₂₃ = 3,781.5, P = .009, respectively). SC patients had longer hospitalizations compared to cannabis users (43.45 ± 54.02 days versus 22.91 ± 31.36 days, U₂₁₉ = 5,701.5, P = .005, respectively), had more previous hospitalizations (3.73 ± 5.05 versus 1.98 ± 5.12, U₂₂₃ = 6,284, P < .001, respectively), and were more likely to be hospitalized by criminal court order (36.7% [n = 22] versus 19.9% [n = 32], χ²₂ = 7.136, P = .028, respectively). SC patients presented with a more severe clinical picture manifested by higher total PANSS scores (82.53 ± 23.05 versus 69.98 ± 19.94, t₉₁ = -2.696, P = .008) in a subset of patients with PANSS scores assessed within a week from admission (n = 30 in the SC group and n = 63 in the cannabis group). No differences were found in physiologic or laboratory measures on admission between the SC and cannabis groups.

CONCLUSIONS

Patients admitted following use of SC are generally younger males who have higher severity of psychotic symptoms at admission, are more likely to be admitted by criminal court order, and require longer hospitalization periods in comparison to cannabis users.