Evidence map›Paper›PMID 37440493›Full record

Trial reportPloS one2023

The effects of caffeine and d-amphetamine on spatial span task in healthy participants.

Faiz M Kassim, J H Mark Lim, Sophie V Slawik, Katharina Gaus, Benjamin Peters, Joseph W Y Lee, Emily K Hepple, Jennifer Rodger, Matthew A Albrecht, Mathew T Martin-Iverson

Open access · goldAbstract readRandomized Controlled Trial
PubMed Full text at PMC Publisher
In one paragraph

Trial report in PloS one, 2023. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 1 paper.

0numbers the graph read from it
0cells of the map it votes in
1citing papers in PubMed
0.4field-weighted citation impact, top 37% of its field
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.

3 · Its place in the literature

Who cites it

1 citing paper in PubMed, 2 citations in OpenAlex.

  1. Review
4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

10 authors at 4 institutions in 3 countries.

Faiz M KassimPsychopharmacology Research Unit, School of Biomedical Sciences, University of Western Australia, Perth, WA, Australia.ORCID 0000-0001-6356-5867
J H Mark LimPsychopharmacology Research Unit, School of Biomedical Sciences, University of Western Australia, Perth, WA, Australia.
Sophie V SlawikFaculty of Human and Health Sciences, Psychology, University of Bremen, Bremen, Germany.
Katharina GausFaculty of Human and Health Sciences, Psychology, University of Bremen, Bremen, Germany.
Benjamin PetersDepartment of Psychiatry, St. Paul's Hospital Millennium Medical College, Addis Ababa, Ethiopia.
Joseph W Y LeePsychiatry, Medical School, University of Western Australia, Perth, WA, Australia.
Emily K HeppleMental Health, North Metropolitan Health Services, Perth, WA, Australia.
Jennifer RodgerExperimental and Regenerative Neurosciences, School of Biological Sciences, University of Western Australia, Crawley, WA, Australia.
Matthew A AlbrechtWestern Australian Centre for Road Safety Research, School of Psychological Science, University of Western Australa, Crawley, WA, Australia.
Mathew T Martin-IversonPsychopharmacology Research Unit, School of Biomedical Sciences, University of Western Australia, Perth, WA, Australia.
The University of Western Australia · AUUniversity of Bremen · DENorth Metropolitan Health Service · AUSt. Paul's Hospital Millennium Medical College · ET

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

Studies that examined the effect of amphetamine or caffeine on spatial working memory (SWM) and verbal working memory (VWM) have used various tasks. However, there are no studies that have used spatial span tasks (SSTs) to assess the SWM effect of amphetamine and caffeine, although some studies have used digit span tasks (DST) to assess VWM. Previous reports also showed that increasing dopamine increases psychosis-like experiences (PLE, or schizotypy) scores which are in turn negatively associated with WM performance in people with high schizotypy and people with schizophrenia. Therefore, the present study aimed to examine the influence of d-amphetamine (0.45 mg/kg, PO), a dopamine releasing stimulant, on SST, DST, and on PLE in healthy volunteers. In a separate study, we examined the effect of caffeine, a nonspecific adenosine receptor antagonist with stimulant properties, on similar tasks.

methodsHealthy participants (N = 40) took part in two randomized, double-blind, counter-balanced placebo-controlled cross-over pilot studies: The first group (N = 20) with d-amphetamine (0.45 mg/kg, PO) and the second group (N = 20) with caffeine (200 mg, PO). Spatial span and digit span were examined under four delay conditions (0, 2, 4, 8 s). PLE were assessed using several scales measuring various aspects of psychosis and schizotypy.

resultsWe failed to find an effect of d-amphetamine or caffeine on SWM or VWM, relative to placebo. However, d-amphetamine increased a composite score of psychosis-like experiences (p = 0.0005), specifically: Scores on Brief Psychiatric Rating Scale, Perceptual Aberrations Scale, and Magical Ideation Scale were increased following d-amphetamine. The degree of change in PLE following d-amphetamine negatively and significantly correlated with changes in SWM, mainly at the longest delay condition of 8 s (r = -0.58, p = 0.006).

conclusionThe present results showed that moderate-high dose of d-amphetamine and moderate dose of caffeine do not directly affect performances on DST or SST. However, the results indicate that d-amphetamine indirectly influences SWM, through its effect on psychosis-like experiences.

trial registrationCLINICAL TRIAL REGISTRATION NUMBER: CT-2018-CTN-02561 (Therapeutic Goods Administration Clinical Trial Registry) and ACTRN12618001292268 (The Australian New Zealand Clinical Trials Registry) for caffeine study, and ACTRN12608000610336 for d-amphetamine study.

Indexed as

CaffeineDextroamphetamineAmphetamineAustraliaDopamineDouble-Blind MethodHealthy VolunteersHumansAmphetamineCaffeineDextroamphetamineDopamine

Identifiers

PMID37440493
PMCPMC10343048
OpenAlexW4384156178

What OpenQuestion holds

Textmetadata
LicenceCC BY
Read underepoch 390

Registered trials

None linked

Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.