Asymmetry in Psychoactive Research: A Bibliometric Study on 15 Psychoactive Drugs

This study (2022) is a bibliometric review of 15 psychoactive drugs from 1960 to 2018 (956,703 publications). Results show heterogeneous patterns of growth for the publications of the selected psychoactive drugs. The literature on legal substances and depressants represented between 60% and 80% throughout the years. Additionally, unexpected regional differences in the scientific output about the selected drugs were found, which might be explained by cultural and political phenomena.

Authors

“Although intended to avoid illicit drug use, national laws and international conventions have limited research on psychoactive drugs. To characterise the evolution of the literature on psychoactive drugs, a bibliometric study of 15 psychoactive drugs from 1960 to 2018 was conducted in which 956,703 academic publications were obtained from Web of Science. Growth patterns were analysed per drug type, legal status and country. Our results show the existence of heterogeneous patterns of growth for the publications of different psychoactive drugs. Strikingly, the literature on legal substances and depressants represented between 60% and 80% throughout the years. We found unexpected regional differences in the scientific output about the selected drugs, which might be explained by cultural and political phenomena. Governments and funding bodies should consider these results when allocating resources to research on psychoactive drugs to optimise the therapeutic applications of these compounds and our understanding of the nervous system.”

Authors: Julia Lebrero-Tatay, Arthur Sebag & Ivan Ezquerra-Romano

Summary

Although intended to avoid illicit drug use, national laws and international conventions have limited research on psychoactive drugs. A bibliometric study of 15 psychoactive drugs from 1960 to 2018 showed that there were heterogeneous patterns of growth for the publications of different psychoactive drugs.

Introduction

When trading and consuming psychoactive drugs, the laws aim to reduce their availability due to perceived societal and individual harm. However, the way in which psychoactive drugs are policed is poorly correlated with their harms.

After 1961, the current laws and restrictions on controlled substances were implemented. These laws were based on a series of national and international conventions, including the 1961 UN Single Convention on Narcotic Drugs, the 1971 UN Convention on Psychotropic Substances and the 1988 UN Convention Against Illicit Traffic in Narcotic Drugs.

The original laws have remained virtually unchanged at a global scale despite the political, social and scientific costs. Scientists face four main hurdles when attempting to study controlled substances: a special licence is required, the substances are not readily available, and they are expensive.

Previous bibliometric studies have highlighted the impact of drug policies on psychoactive substances research, but have hardly discussed the impact of historical and socio-political factors on publication trends of psychoactive substances.

Our study aims to compare publication trends among different psychoactive substances to reveal the existing gaps in this field and inform future policies and funding strategies.

We expected publications on drugs classified into the most restrictive categories to show unstable patterns of growth and periods of decline, and expected regional differences in the growth patterns and productivity.

Search Protocol

The number of publications per year and top contributing countries for each drug were obtained using the Web of Science Core Collection.

After pilot searching, a series of topic keywords were determined. The top 5 contributing countries for each drug were determined using WoS0 analysis tools.

Selection criteria

We selected psychoactive drugs according to two criteria: (1) to include at least one drug per drug schedule or class according to the legal classifications used in the US and UK as of July 2019; and (2) to assess similarities and differences between and within psychoactive drug categories.

Drug laws changed substantially during the 70s, so data from the period before and during this period were excluded.

The studies on drugs that met the previous criteria were individually checked to exclude studies unrelated to the drug.

Analysis

A curve was fitted to the number of publications per year for a topic to show the pattern of growth of publications in a topic.

The growth rate of y was fitted to a non-linear equation using the curve_squares function from the scipy library and the R2 value was obtained to assess goodness of fit.

We hypothesized that stricter regulations on the trade and consumption of a drug would result in publications patterns which deviated from an exponential curve.

The Relative Growth Rate was calculated for all drugs per decade from 2010 to 2018 using the following equation.

The RGR is the natural logarithm of the number of published papers over time. A positive RGR indicates an increase in the number of published papers.

Results

In the 1960s, the number of published papers on most drugs increased subtly but steadily. In the 1970s, the number of published papers on heroin, methadone and benzodiazepines increased steeply, while the number of published papers on LSD and psilocybin decreased.

We fitted an exponential curve to the growth rate of publications for each drug. Psilocybin showed the highest growth rate, 0.17, followed by all other drugs with 0.04 to 0.08 growth.

The growth patterns of publications for the studied drugs show different patterns, with alcohol having the best fit to an exponential curve, and benzodiazepines having the poorest fit to an exponential curve.

We used the Relative Growth Rate (RGR) standardised measure to analyse the productivity and growth of published papers in the field of psychoactive drugs from 1960 to 2018. The literature on alcohol, legal substances, depressants, psychedelics and Schedule I – V drugs represented between 60% and 80% of total literature from 1960 to 2018, whereas the literature on LSD represented 5 – 10% during the 1960s, but dropped during the 70s, reaching 1.5% in 1978.

The US has been the main contributor to the literature on alcohol, cannabis, MDMA, LSD and cocaine from 1960 to 2018. The top five contributing countries vary across drugs, with the US dominating the literature on all five drugs.

Discussion

Our bibliometric analysis showed that the literature of 15 different psychoactive drugs shows heterogenous growth patterns, is uneven among the selected drugs, and has regional differences in the contribution of countries to the literature.

We hypothesised that the less control imposed over a drug, the higher the R2 value from fitting its curve to an exponential equation. However, the results suggest a far more complex series of growth patterns.

The number of scientific publications follows an exponential growth, but there are periods of plateau or decay within the publication patterns. This suggests there are factors affecting this natural growth. MDMA was studied as a treatment for psychedelic use, but the US banned it in 1985 and the UK brewing industry sponsored anti-MDMA campaigns. This impacted MDMA research and the number of papers published on MDMA decreased after 1995.

The uneven research output among the selected drugs shows that alcohol has dominated research over the years, and that depressants and stimulants account for between 70% and 90% of the total literature of the selected drugs. This asymmetry may skew our understanding of the nervous system.

The US dominates the psychoactive drug literature, while no Asian country is listed within the top five contributor countries for cannabis, ketamine, LSD nor MDMA literature. This could be explained by socio-political regional differences.

Italy is the third top contributor to the literature on cannabis, Ethiopia and Yemen are amongst the top 5 contributors to literature on khat, and Switzerland is the third contributor to literature on psilocybin due to the legal use of psilocybin and LSD in the 1980s and 1990s.

Our bibliometric study of 15 different psychoactive substances shows that research on psychoactive substances is asymmetric. Restrictive laws and social stigma seem to particularly hinder research on psychoactive substances, and government and funding bodies should consider these side-effects of drug laws and continue promoting drug research even for highly regulated substances.