Evidence submitted by Professor P. Murphy, Department of Psychology, Edge Hill University DRU0092

Submission to the Home Affairs Select Committee

Psychological harm arising from the use of illegal drugs

Professor Philip N. Murphy

Department of Psychology, Edge Hill University, UK.

Introduction

1. Research into psychological issues concerning the use of both legal and illegal substances has been an important part of the research portfolio of Edge Hill University since 1995. Our published research has addressed psychological issues arising from the consumption of alcohol, heroin, ecstasy (MDMA), and cannabis, and will shortly include research into long-term effects of psychedelic drug use. In addition to publication in leading scientific journals and presentations at important conferences, our research has frequently received attention in both print and broadcast media. The term ‘psychological issues’ here covers such things as psychological variables which predict good or bad treatment outcomes, responses to alcohol related cues which may enhance its consumption, and impairments to psychological functioning which may be related to drug consumption. This present submission is concerned with the last of these categories, and focuses upon impairments in cognitive functioning in users of ecstasy (MDMA) and cannabis, compared to nonusers of these drugs.

2. The Crime Survey for England and Wales (CSEW) 2019 estimated that approximately 10.2 million people aged between 16 and 59 years of age had used cannabis in England and Wales at some time in their lives, with 2.5 million people having used it in the previous year, and approximately 1.3 million people having used it in the month prior to data collection. The corresponding figures for ecstasy were approximately 3.3 million, 524,000, and 108,000 people [1]. Consequently, issues of harm to psychological functioning arising from the use of these drugs may potentially affect a large proportion of the United Kingdom population.

3. The term cognitive functioning in this submission refers to processes concerning memory, reasoning, and the regulation of emotion, and includes consideration of the brain structures and processes underpinning these psychological functions. The present objective is to briefly present summaries of existing evidence for such impairments, with the aim of explaining why such evidence should be considered important in the shaping of policies towards the use of these drugs. Consequently, it is important to address also some abiding criticisms of such research which have sometimes been presented as arguments to diminish the weight which should be given to it.

4. In addressing the cognitive processes previously described, it should be emphasised that the present submission is concerned with non-psychiatric populations of drug users, as opposed to users who have been diagnosed with psychiatric disorders which have, in turn, been regarded as related in some way to their drug use. It is noted here that a strong body of literature exists concerning the relationship between cannabis use and psychosis [2], with the evidence for a link between ecstasy use and psychosis being less strong [3]. However, the remainder of this submission will be concerned with evidence for impairments in psychological functioning related to cannabis and ecstasy use in non-psychiatric populations.

Psychological harm related to cannabis and/or ecstasy use in non-psychiatric populations

Background

5. This section will draw predominantly from published scientific reviews of existing evidence, with reference to primary studies where appropriate, to elaborate upon specific points. A distinction can be made between primary research studies which examine changes in psychological functioning in the immediate period following the administration of a drug to human participants occurring in either a laboratory or clinical setting, and studies which examine changes in such functioning without drug administration in the testing situation. These two types of studies are essentially addressing different questions, with the latter being concerned with intermediate to long-term effects in abstinent users.

6. Although short-term effects on psychological functioning following drug administration may have important implications, such as those for driving a car or operating machinery following alcohol consumption, their existence and implications can be more readily demonstrated and understood than those concerning intermediate and long-term effects in abstinent users. The demonstration of impaired psychological functioning in currently abstinent users of a drug indicates the presence of longer - term dysfunction than that associated with intoxication following administration. Furthermore, the implications of such longer-term dysfunction for a person’s well-being, and for the well-being of those around them and for society more generally, may be less apparent than for short-term dysfunction occurring during intoxication. This submission is concerned with evidence gathered from currently abstinent users of cannabis and ecstasy, with abstinence defined as the lack of drug administration for the purposes of testing. Questions concerning the duration of abstinence prior to testing would require greater wordage to examine properly than is available here.

Cannabis

7. Reviews of the evidence for impaired cognitive functioning in abstinent cannabis users have highlighted the learning and memory of language based material as an area of functioning where abstinent cannabis users have been shown to perform worse than nonusers [4-7]. It is important to note that these impairments in performance were frequently reported to be related to the quantity and frequency of cannabis used, with greater use being related to greater impairment. Higher levels of impairment were also related to earlier onset ages of use. Although there is always a risk that the use of other drugs than cannabis could have a confounding effect on results, researchers have generally been careful to design their studies and to use forms of statistical analysis, which enable the minimisation of this risk [8-9]. The replication of findings of impaired functioning in users compared to nonusers serves to increase the confidence which may be invested in the conclusion that a true effect exists.

8. There are some areas of cognitive functioning where the evidence for impairments in abstinent cannabis users presents an overall contradictory picture. These include the areas of working memory and executive functioning [5, 7]. Working memory may be colloquially described as operating in the short-term across our sensory modalities to enable a person to function appropriately in their immediate environment. The construct of executive functioning in psychology can be linked to that of working memory, but with additional components concerning decision making and problem solving. The diversity of functions subsumed into both constructs may be responsible for the contradictory nature of findings reported, with some functions being vulnerable to impairment whilst other are not. In relation to working memory, it has been reported that synthetic cannabinoids can have more disruptive effects on functioning than the consumption of traditional plant based cannabis [7, 10]. Synthetic cannabinoids are manufactured compounds which generally have a more potent affinity for the same receptors in the brain as those acted upon by traditional forms of cannabis [11]. A body of scientific evidence for the disruptive effects of synthetic cannabinoids on psychological functioning and health has now developed and been reviewed in several places [12-13].

9. Reviews of differences in brain structure and functioning between cannabis users and nonusers have highlighted differences in several areas [7, 14-16]. In particular, a structure called the hippocampus has emerged as one where differences in both structure and functioning have been reported. The hippocampus plays an important role in memory functioning, so that anomalies here are consistent with the differences in memory performance previously described. Structural differences in the cerebral cortex (which supports higher cognitive functions associated with consciousness) between cannabis users and nonusers have been reported to be related to the onset age of cannabis use, with greater differences occurring with younger onset of use [17]. It should be noted that differences in brain functioning between users and nonusers during the performance of cognitive tasks have been reported, even where the quality of task performance did not differ between the two groups [18-19]. This has been suggested to show that cannabis users may need to recruit additional brain resources to maintain adequate task performance, although this interpretation of such findings is not universally accepted.

Ecstasy (MDMA)

10. Several reviews of primary studies have reported impairments in some aspects of cognitive functioning in abstinent users of the drug ecstasy (MDMA), compared to nonusers [20-26]. These impairments have tended to be present in the learning and memory of language based material, and some aspects of working memory such as the processing of information about spatial aspects of the environment. The latter area of impairment has been linked with distortions in perception of one’s own movement [23]. More generally, spatial information concerning a person’s immediate environment is important in such things as driving a vehicle or operating machinery. Another area of impaired memory performance in ecstasy users versus nonusers has been that of prospective memory, which is concerned with remembering to do something at some time in the future [23- 24, 27]. However, not all aspects of working memory have been reported to show consistent impairments in ecstasy users, such as the shifting of attention and the inhibition of responses to certain trigger stimuli [20, 24].

11. Researchers have generally shown good awareness of the possibility that reported impairments in cognitive functioning in ecstasy users could be due to the use of other drugs, or a failure to control for differences in variables such as intelligence (measurable as IQ scores) and education between groups of users and nonusers. The control of potentially confounding variables such as these has been examined closely by some reviewers of primary research studies [20-21, 26]. It has been noted in these reviews, for example, that as many ecstasy users have also used cannabis, researchers may have one control group of participants reporting no illegal drug use, and a further control group who have used cannabis, but not ecstasy. Consequently, significant differences in performance between a third group who will have used both ecstasy and cannabis, and the two control groups, can be reported with greater confidence as being related to ecstasy use. Differences between participant groups in IQ, age, and other quantifiable variables are frequently controlled by a range of statistical techniques. In summary, primary research reports of impaired cognitive functioning in ecstasy users compared to nonusers have generally taken account of a number of potentially confounding influences on their results.

12. The control of emotions is frequently referred to as mood regulation in the scientific literature. Enhanced positive moods following the self-administration of ecstasy, followed by serious depression in the following days, are both noted in the scientific and popular literature concerning ecstasy use [24, 28]. However, disturbances to mood in the form of anxiety and depression in the intermediate and long-term following the initiation of regular ecstasy use have also been noted in the scientific literature [23-24, 29-31]. Researchers acknowledge that self-reported attributions to ecstasy use of adverse mood states beyond one week from an episode of ecstasy self-administration, is open to misinterpretation in terms of the influence of other drugs used, and pre-existing disturbances. However, the reporting of emotional disturbances is not rare in ecstasy users [30], and has been shown to be independent of their concern about the effects of the drug [31]. This latter finding argues against the view that such disturbances constitute a self-fulfilling prophecy arising from adverse media coverage of ecstasy use.

13. Reviews of primary studies have highlighted that ecstasy users have been shown to demonstrate a range of differences in brain structure and functioning compared to nonusers of the drug [22-25]. These differences have included damage to the structural integrity of neurons (i.e. the information processing cells of the brain) [32], differences in the functioning of brain pathways of neurons using serotonin as a neurotransmitter (i.e. the chemical which facilitates communication between neurons in that pathway) [33], and differences in blood flow within certain regions of the brain, which are consistent with differences in information processing activity in these brain areas between ecstasy users and nonusers [34-35]. These latter two studies report that even where performance levels on a task requiring information processing of some sort did not differ between users and nonusers, significant differences in regional cerebral blood flow between users and nonusers were still observed. These findings may be interpreted as showing that ecstasy users needed additional brain resources to maintain equivalent performance to nonusers, although this interpretation is not universally accepted.

14. Issues concerning the relationship of differences in brain structure and functioning between ecstasy users and nonusers and such things as duration and dosages of ecstasy used, age of onset of use, and the duration of differences once ecstasy use has been terminated, have been carefully researched, but have revealed a complex body of findings which cannot be addressed in the space available here. For the purposes of the present submission, it is important to summarise that structural and functional differences, consistent with differences in cognitive functioning and mood regulation, have been widely reported in the scientific literature [20-26].

General Discussion

15. It will be apparent from this submission that the body of scientific literature on impairments in psychological functioning in users of cannabis and ecstasy, with regard to cognitive performance and mood regulation, and with regard to the brain structures and processes underpinning these functions, is highly complex. This present review is not put forward as being exhaustive, but is presented to highlight the importance of considering the evidence for such impairments in the wider context of drug related harm. The responses of researchers to the potentially confounding influences of other drug use and differences in such things as IQ scores between users and nonusers, has previously been addressed in this submission. However, there are some general points which need to be considered concerning the evidence presented here, which relate to criticisms which are often made of its strength and relevance.

16. The criticism is sometimes made that the evidence for impaired cognitive performance in cannabis and ecstasy users comes from laboratory studies using artificial tasks which have little relevance to everyday life. Furthermore, although differences in performance between users and nonusers may pass the test of ‘statistical significance’ used in scientific research, the magnitude of the difference (referred to as the effect size) is often small and has no implications for everyday life. In response to these criticisms, it may be said that laboratory tasks break down the cognitive abilities used in everyday tasks into separately recognisable units for which performance may be measured. Consequently, their use may be seen as a strength which enables precision in identifying abilities which are impaired and those which are not. Furthermore, laboratories offer a protected environment free of distraction, so that a measure of performance may be gained without being contaminated by other demands. Consequently, a small effect size related to impaired performance in a laboratory does not mean that no problem can be assumed to exist in a pressurised real world setting (e.g. Air Traffic Control, a factory, etc.), where extraneous pressures may exacerbate the potential effects of drug related influences on performance.

17. An ideal experiment with human participants into impaired cognitive functioning related to either cannabis or ecstasy use would involve taking two or more groups of nonusers, and requiring one of the groups to take a specified amount of the drug with a particular dosing frequency, for a specified period of time which would probably need to be a matter of years. There would also need to be very careful daily control of other variables which might exert an effect on cognitive functioning (e.g. alcohol consumption). At the specified time, all participants would be tested for evidence of impaired cognitive and brain functioning attributable to the experimental manipulation (i.e. drug administration or not). Such a research study would of course be unethical, immoral, illegal, and impractical. It is for these reasons that research into impaired psychological functioning with drug users relies heavily upon pre-existing groups of users and nonusers. These are commonly referred as a cross-sectional research designs. As there can be no random allocation of participants to such groups, the strict demands of experimental methodology cannot be met, and cause and effect in a scientific sense cannot be claimed with regard to drug use and any functional impairments identified. Consequently, it is common to report that such impairments have been found to be ‘related’ to the use of a drug in order to avoid claiming causality. The need to use pre-existing groups opens the door to potential confounds in the data such as the effects of using other drugs, and pre-existing inter-group differences in such things as IQ. This is why it has been emphasised in earlier sections of this submission that researchers in this field have generally been attentive to the influence of such potential confounds.

18. Despite the limitations previously described, without the use of cross-sectional designs in research into drug related impairments in psychological functioning it would not be possible to develop a body of knowledge of potentially important adverse effects of drug use in the lives of many people. In this context, the ability of findings to be replicated becomes important, and the reviews of primary studies cited throughout this submission have noted the prevalence of replicated findings in the areas of functioning discussed. The prevalence of cannabis and ecstasy use cited in the opening section of this submission [1] indicates the large number of people potentially adversely affected by these drugs. It may be argued that the impact of these effects is not simply limited to the immediate activities of these people. A recent review published by the British Psychological Society proposed that impaired cognitive functioning resulting from drug use could be a factor making it difficult for some people to leave a situation of poverty [36].

19. In conclusion, drug related harm may come in many forms. Death must inevitably be regarded as the most serious of these, and risks of serious illnesses arising from drug use must be given appropriate concern. The risks to psychological functioning reviewed in this submission, which are related to two of the more commonly used drugs prohibited under the Misuse of Drugs Act 1971, are inevitably more subtle and less visible than death and serious illness, but are still capable of having a debilitating effect in people’s lives. Consequently, they require serious consideration in the formulation of policies to address the use of drugs in our society.

References

[1] Drug Misuse: Findings from the 2018-19 Crime Survey for England and Wales. Statistical Bulletin21/19. London: Home Office Crown Copyright 2019. (See Table 1.04).

[2] Marconi, A., Forti, M.D., Lewis, C.M., Murray, R.M. Vassos, E. Meta-analysis of the association between the level of cannabis use and risk of psychosis. Schizophrenia Bulletin 2016; 42: 1262-1269.

[3] Lappin, J.M., Sara, G.E. Psychostimulant use and the brain. Addiction 2019; 114: 2065-2077.

[4] Solowj, N., Battisti, R. The chronic effects of cannabis on memory in humans: a review. Current Drug Abuse Reviews 2008; 1: 81-98.

[5] Broyd, S.J., Hendrika, H.vH.,, Beale, C., Yücel, M., Solowij, N. Acute and chronic effects of cannabinoids on human cognition – a systematic review. Biological Psychiatry 2016; 79: 557-567.

[6] Volkow, N.D., Swanson, J.M., Evins, A.E., DeLisi, L.E., Meier, M.H., Gonzalez, R., Bloomfield, M.A.P., Curran, H.V., Baler, R. Effects of cannabis use on human behavior, including cognition, motivation, and psychosis: A review. Journal of the American Medical Association – Psychiatry 2016; 73: 292-297.

[7] Murphy, P.N. Some psychobiological implications of the consumption of cannabis. In P.N. Murphy (Ed.) The Routledge International Handbook of Psychobiology. Abingdon, Oxon: Routledge 2018. Chapter 19

[8] Croft, R.J., Mackay, A.J., Mills, A.T.D., Gruzelier, J.G.H. The relative contributions of ecstasy and cannabis to cognitive impairment. Psychopharmacology 2001; 153: 373-379.

[9] Murphy, P.N., Erwin, P.G., MacIver, L., Fisk, J.E, Larkin, D., Wareing, M., Montgomery, C., Hilton, J., Tames, F.J., Bradley, B., Yanulevitch, K., Ralley, R. The relationships of ‘ecstasy’ (MDMA) and cannabis use to impaired executive inhibition and access to semantic long term memory. Human Psychopharmacology: Clinical and Experimental 2011; 26: 460-469.

[10] Cohen, K., Kapitány-Fövény, M., Mama, Y., Arieli, M., Rosca, P., Demetrovics, Z., Weinstein, A. The effects of synthetic cannabinoids on executive function. Psychopharmacology 2017; 234: 121-1,134.

[11] Thomas, B.F., Wiley, J.L., Pollard, G.T., Grabenauer, M. Cannabinoid designer drugs: effects and forensics. In R.G. Pertwee (ed.) Handbook of Cannabis. Oxford: Oxford University Press 2014. Chapter 40.

[12] Cohen, Weinstein, A.M. Synthetic cannabinoids (SCs): current knowledge, psychobiology and clinical aplications. In P.N. Murphy (Ed.) Psychobiolpogical Issues in Substance Use and Misuse. London and New York: Routledge 2021. Chapter 7.

[13] Schifano, F. et al. Psychobiological, medical, and psychiatric implications of new/novel psychoactive substance (NPS) use. In P.N. Murphy (Ed.) Psychobiolpogical Issues in Substance Use and Misuse. London and New York: Routledge 2021. Chapter 11.

[14] Lorenzetti, V., Lubman, D.I., Fornito, A., Whittle, S., Takagi, M.J., Solowij, N., YÜcel, M. The impact of regular cannabis use on the human brain: a review of structural neuroimaging studies. In P.M. Miller, S.A. Ball, M.E. Bates, A.W. Blume, K.M. Kampman, D.J. Kavanagh, M.E. Larimer, N.M. Petry, P. De Witte (eds) Comprehensive Addictive Behaviors and Disorders: Biological Research on Addiction. San Diego: Elsevier 2013. Chapter 69.

[15] Lorenzetti, V., Solowij, N., Yücel, M. The role of cannabinoids in neuroanatomic alteratuions in cannabis users. Biological Psychiatry, 2016; 79: e17-e31.

[16] Rocchetti, M., Crescini, A., Borgwardt, S., Caverzasi, E., Politi, P., Atakan, Z., Fusar-Poli, P. Is cannabis neurotoxic for the healthy brain ? A meta-analytical review of structural brain alterations in non-psychotic users. Psychiatry and Clinical Neuroscience, 2013; 67: 483-492.

[17] Lopez-Larson, M.P., Bogorodzki, P., Rogowska, J. et al. Altered prefrontal and insular cortical thickness in adolescent marijuana users. Behavioural Brain Research 2011; 220: 164-172.

[18] Padula, C.B., Schweinsburg, A.D., Tapert, S.F. Spatial working memory performance and fMRI activation interventions in abstinent adolescent marijuana users. Psychology of Addictive Behaviors 2007; 21: 478-487.

[19] Tapert, S.F., Schweinsburg, A.D., Drummond, S.P.A., Paulus, M.P., Brown, S.A., Yang, T.T., Frank, L.R. Functional MRI of inhibitory processing in abstinent adolescent Marijuana users. Psychopharmacology 2007; 194: 173-183.

[20] Murphy, P.N., Wareing, M., Fisk, J.E. Executive Working Memory Deficits in Abstinent Ecstasy/MDMA Users: A Critical Review. Neuropsychobiology 2009; 60: 159-175.

[21] Murphy, P.N., Bruno, R., Wareing, M., Ryland, I., Fisk, J.E., Montgomery, C. The effects of ecstasy (MDMA) on visuospatial memory performance: Findings from a systematic review with meta-analysis. Human Psychopharmacology: Clinical and Experimental 2012; 27: 113-138.

[22] Parrott, A.C. Human psychobiology of MDMA or ‘ecstasy’: an overview of 25 years of empirical research. Human Psychopharmacology: Clinical and Experimental 2013; 28: 289-307.

[23] Parrott, A.C. MDMA, serotonergic neurotoxicity, and the diverse functional deficits of recreational ‘Ecstasy’ users. Neuroscience and Biobehavioral Reviews 2013; 37: 1466-1484.

[24] Roberts, C.A., Montgomery, C. What is the evidence for psychobiological harm from the use of ‘ecstasy’ (MDMA). In P.N. Murphy (ed.) The Routledge International Handbook of Psychobiology. London: Routldege 2018. Chapter 20.

[25] Montgomery, C.,Roberts, C.A. The neurobiological mechanisms underpinning MDMA and impaired psychological functioning: A review of studies with human participants. In P.N. Murphy (Ed.) Psychobiological Issues in Substance Use and Misuse. London and New York: Routledge 2021. Chapter 5.

[26] Murphy, P.N,, Ryland, I., Wolohan, F., & Bartholomew, J. ‘Ecstasy’ (MDMA) and visuospatial processing: a follow-up systematic review. In P.N. Murphy (Ed.) Psychobiolpogical Issues in Substance Use and Misuse. London and New York: Routledge 2021. Chapter 12.

[27] Gallagher, D.T., Hadjiefthyvoulou, F., Fisk, J.E., Montgomery, C., Robinson, S., Judge, J. Prospective memory deficits in in illicit polydrug users are associated with the average long-term typical dose of ecstasy typically consumed in a single session. Neuropsychology 2014; 28: 43-54.

[28] Curran, H.V., Travill, R.A. Mood and cognitive effects of 3,4 methylenedioxymethamphetamine (MDMA, “ecstasy”): Weekend “high” followed by mid-week “low.” Addiction 1997; 92: 821–31.

[29] Murphy, P.N., Wareing, M., Fisk, J.E. Users' perceptions of the risks and effects of taking MDMA (Ecstasy). Journal of Psychopharmacology 2006; 20: 447-455.

[30] Craig, L., Fisk, J.E., Montgomery, C., Murphy, P.N., Wareing, M. Is emotional intelligence impaired in ecstasy-polydrug users. Journal of Psychopharmacology 2010; 24: 221-231.

[31] Fisk, J.E., Murphy, P.N., Montgomery C., Hadjiefthyvoulou, F. Modelling the adverse effects associated with ecstasy use. Addiction 2011; 106: 798-805.

[32] de Win, M.M.L., Reneman, L., Jager, G., Vlieger, E-J.P., Olabarriaga, S.D., Lavini, C., Bisschops, I., Majoie, C.B.L.M., Booij, J., den Heeten, G.J., van den Brink, W. A prospective cohort study on sustained effects of low dose ecstasy use on the brain in new ecstasy users. Neuropsychopharmacology 2007; 32: 458-470.

[33] Kish SJ, Lerch J, Furukawa Y, Tong J, McCluskey T, Wilkins D, Houle S, Meyer J, Mundo E, Wilson AA, Rusjan PM, Saint-Cyr JA, Guttman M, Collins DL, Shapiro C, Warsh JJ, Boileau I. Decreased cerebral cortical serotonin transporter binding in ecstasy users: a positron emission tomography/[11C]DASB and structural brain imaging study. Brain 2010; 133: 1779-1797.

[34] Roberts, C.A., Montgomery, C.A. Cortical oxygenation suggests increased effort during cognitive inhibition in ecstasy polydrug users. Journal of Psychopharmacology 2015; 29:1170–1181.

[35] Roberts C.A., Montgomery C.A. fNIRS suggests increased effort during executive access in ecstasy polydrug users. Psychopharmacology 2015; 232:1571–1582.

[36] Murphy, P.N., Burford, D., McWha, I., Sheehy-Skeffington, J., Byrne, C. From Poverty to Flourishing: Agency and Empowerment. Leicester, UK: British Psychological Society 2021.

Appendix

Psychological harm arising from the use of illegal drugs

Glossary of Terms

Cannabinoid. A chemical compound found in the cannabis sativa plant, and may consequently be present in supplies of cannabis. These compounds have an affinity for some receptors in the brain, thus leading to effects on psychological functioning and behaviour.

Cerebral cortex. The outer layer of the brain which supports higher level psychological functions concerned with thinking and consciousness.

Confounding variable. A variable which may influence the results obtained from data collected in such a way as to lead to a wrong conclusion, or prevent a clear conclusion from being made.

Effect size. The magnitude of change measured in one variable (e.g. memory performance) related to the change in another variable (e.g. cannabis use or not).

Hippocampus. This is a brain structure strongly implicated in memory. It has strong functional connections with other brain areas concerned with emotion.

MDMA. An abbreviation of 3,4-methylenedioxymethamphetamine, which is the defining element of black market supplies of ‘ecstasy’.

Neuron. Neurons exist throughout the nervous system. Within the brain it may be regarded as an information processing cell involved in all aspects of consciousness and the control of bodily systems.

Neurotransmitter. These are endogenous chemicals which enable the transmission of activity from one neuron to another within the nervous system.

Primary studies. This term refers to published reports of original research findings.

Statistical significance. It is common for the statistical analysis of research findings to focus upon the probability of obtaining the results in question under the assumption (or null hypothesis) that there is no real effect. An example would be the assumption that any performance different on a task between two participant groups was simply random variation. By convention, if the estimated probability of obtaining the present results is less than 5% (with 0% representing ‘impossible’ and 100% representing ‘inevitable’), then the results is said to be statistically significant and due to something more than just random variation.

Synthetic cannabinoids. These are artificially created compounds similar in structure and effect to naturally occurring cannabinoids. They often have a stronger affinity for the same receptors in the brain as naturally occurring cannabinoids, consequently making their effects more potent.

Working memory. This is a psychological construct representing memory functioning across sensory modalities which enable a person to deal with the immediate demands of the social and physical environment. It may be described colloquially as memory for dealing with the here and now.

March 2022