Psychedelics Glossary

Glossary

A comprehensive glossary of terms relating to psychedelics.

  • Psychedelics and related compounds
  • Psychedelic-assisted therapy
  • Neuro-, pharma-, and psychological mechanisms
  • Mystical states


Publicly accessible, and created for the purposes of the Psychedelic Practitioner Foundations Programme. 
A comprehensive glossary of terms relating to the Psychedelic Practitioner Foundations Programme. 
5HT-2A (Serotonin-2A) Receptor A subtype of serotonin receptor involved in the mechanism of action of many psychedelics. 
5-MeO-DMT A powerful and fast-acting psychedelic compound found in certain toads and plants, often used in therapeutic settings for its intense and brief effects. 
Acceptance and Commitment Therapy (ACT) A form of psychotherapy that uses acceptance and mindfulness strategies together with commitment and behavior-change strategies to increase psychological flexibility. 
Active Placebo A placebo that mimics some of the side effects of the experimental treatment to help maintain blinding. 
Adjunct Something (for example a treatment) added to something else as a supplementary rather than an essential part. 
Adverse Childhood Experiences (ACEs) Adverse Childhood Experiences (ACEs) are “highly stressful, and potentially traumatic, events or situations that occur during childhood and/or adolescence. They can be a single event, or prolonged threats to, and breaches of, the young person’s safety, security, trust or bodily integrity.” (Young Minds, 2018).
Aetiology The cause, set of causes, or manner of causation of a disease or condition 
Affinity The strength of binding between a drug and its receptor. 
Altered States of Consciousness Any condition which is significantly different from a normal waking state, including those induced by drugs, meditation, hypnosis, or extreme physical conditions. 
Amygdala A brain structure involved in physiological responses to stimuli, especially fear and pleasure responses. 
Animism The belief that objects, places, and creatures all possess a distinct spiritual essence. 
Antidepressant Discontinuation Syndrome Symptoms that can occur upon the abrupt discontinuation or rapid tapering of antidepressants. 
Antipsychotics Medications used to manage psychosis, including delusions, hallucinations, and disorders like schizophrenia. 
ARC Framework An ethical framework used to categorize challenges or dilemmas in psychedelic therapy under three main headings: Access, Reciprocity, and Conduct. 
Associative Strength The degree of correlation between the activities of different brain regions. 
Atherosclerosis A disease where plaque builds up inside arteries, leading to reduced blood flow. 
Attachment Styles Patterns of attachment behaviour shown by individuals in relationships, which are thought to be formed early in life and influence emotional bonds in adulthood. 
Attrition Rate The proportion of participants who drop out of a study over time.
Ayahuasca A traditional South American psychoactive brew, containing DMT, used in healing and spiritual practices. 
Basic Science (In medicine) Research aimed at increasing fundamental knowledge and understanding of the physical, chemical, and functional mechanisms of life processes and disease. 
BDNF (Brain-Derived Neurotrophic Factor) A protein involved in the survival, development, and function of neurons in the brain. 
Behaviourism A theoretical approach that focuses on observable behaviours and the ways they can be learned or unlearned. 
Benzodiazepines A class of psychoactive drugs known for their calming effect, often prescribed for anxiety. 
Big Five Personality Traits The most widely studied factors  of personality: openness, conscientiousness, extraversion, agreeableness, and neuroticism. Often referred to by their acronym OCEAN.
Biopsychosocial Framework An approach that considers biological, psychological, and social factors and their complex interactions in understanding health, illness, and healthcare delivery. 
Black & White Thinking Cognitive distortion where situations and people are viewed in extremes, with no middle ground. 
Blinding Keeping study participants and/or researchers, unaware of which treatment the participants are receiving to prevent bias. 
Bottom-Up Processing Cognitive processing that involves sensory input driving perception and other cognitive functions. 
Boundary Violations Actions that breach the appropriate limits set within a therapeutic relationship. 
CAPS-5 (Clinician-Administered PTSD Scale for DSM-5) A structured interview for assessing post-traumatic stress disorder (PTSD). 
Categorical Classification A system of categorising mental health disorders into distinct categories based on specific criteria. 
Causal Networks Complex systems of interacting factors that contribute to the behaviour of a complex system (such as health or illness). 
Causality vs. Correlation The distinction between a cause-and-effect relationship (causality) and a relationship where two variables are related but not necessarily causally linked (correlation). 
Challenging Psychedelic Experiences Difficult or adverse experiences that occur during or after the use of psychedelic substances. 
Change Mechanisms The processes or factors that are believed to bring about therapeutic change in psychotherapy. 
Chlorpromazine An antipsychotic medication used to treat schizophrenia and other psychotic disorders. 
Classic Psychedelics Psychedelic substances such as LSD, psilocybin, and DMT, known for their profound effects on perception, cognition, and emotion. 
Claustrum A thin, irregular sheet of neurons, thought to play a role in coordinating activity across different parts of the brain. 
Clinical Development The process of conducting clinical trials to evaluate the safety, efficacy, and tolerability of a compound, along with determining the optimal dose and regimen. 
Clinical Research Studies or trials in humans aimed at evaluating the effects, risks, and benefits of medications or medical interventions. 
Clinical Trial Registry A database of clinical studies conducted around the world, where researchers must register their trial and its outcomes. 
Coercive Control A pattern of behaviour that seeks to take away the victim's liberty or freedom, to strip away their sense of self. 
Cognitive Behavioral Therapy (CBT) A type of psychotherapeutic treatment based on a model of the interaction between thoughts, feelings, behaviours, and physiological responses, and how they interact to bring about health or ill-health, developed by Aaron T. Beck. 
Cognitive Dissonance The mental discomfort experienced by a person who holds two or more contradictory beliefs, behaviours, ideas, or values at the same time. 
Cognitive Flexibility The ability to appropriately adjust one's behavior according to a changing environment 
Cognitive Rigidity A lack of cognitive flexibility; an inability to adapt thinking and behavior to new, changing, or unexpected events. 
Collaborative Care A model of care where multiple healthcare providers work together to deliver comprehensive care to patients, involving systematisedcommunication and coordination. 
Common Factors Elements that are present across various forms of psychotherapy, which contribute to the effectiveness of the therapeutic process. 
Comorbidity The simultaneous presence of two or more diseases or medical conditions in a patient. 
Complexity Science An interdisciplinary field studying how relationships between parts of a system give rise to the system's collective behaviours and how the system interacts with its environment. 
Conditioned Fear Memory A learned response to a previously neutral stimulus that has been repeatedly paired with an aversive stimulus. 
Conflicts of Interest (COI) Situations where personal or financial considerations may compromise or bias professional judgement and objectivity. 
Confounding Variables Variables that can interfere with the relationship between the independent and dependent variables, potentially leading to erroneous conclusions. 
Construct Validity The extent to which a test measures what it claims to be measuring. 
Contextual Mismatch A situation where an individual's environment or circumstances do not align with their needs or characteristics, potentially leading to distress or maladjustment. 
Continuous vs. Categorical Different approaches to classification, where continuous refers to a spectrum and categorical refers to distinct groups. 
Contraindicated Medical conditions or treatments that make a particular procedure or medication inadvisable. 
Corrective Experiences Experiences that help to correct previous maladaptive behaviours or thoughts, often occurring in the context of therapy. 
Countertransference The emotional reaction of the therapist to the patient. 
Critical Learning Periods Specific times during which the brain is particularly receptive to learning new information or skills. 
Declarative Memory This is the type of memory that you can consciously recall and ‘declare’. It involves facts and events and is also known as explicit memory.  
Default Mode Network (DMN) A network of interacting brain regions that is active when a person is not focused on the outside world, often associated with daydreaming and self-referential thoughts. 
Delirium An acute onset of confusion, hallucinations, and mood and anxiety changes, usually caused by illness or drug toxicity. 
Depersonalization A feeling of being disconnected from one's own body, thoughts, or identity. 
Derealization An altered perception where the external world feels unreal or detached. 
Dialectical Behavior Therapy (DBT) A type of cognitive-behavioural therapy that combines strategies like mindfulness and acceptance with efforts to change behaviour. Originally developed to treat people with a diagnosis of ‘personality disorder’.
Dissociative Substances that cause a sense of disconnection from reality or one's own body. 
Diversifying Experiences Life events that are extreme, unexpected, and represent inflection points, leading to significant changes in perspective or behaviour. 
DMT (Dimethyltryptamine) A powerful psychedelic compound found in many plants and animals, and known for its short-acting but intense visual and auditory hallucinogenic effects. 
Dopamine A neurotransmitter involved in many brain processes, including mood regulation and reward. 
DSM (Diagnostic and Statistical Manual of Mental Disorders) The standard classification of mental disorders used by mental health professionals in the U.S. 
Dualism The belief that mind and body are distinct and separable entities. 
Duluth Model A behavioral change model developed to reduce domestic violence against women, characterized by its "Power and Control Wheel" that outlines different forms of abuse. 
Dynamical Systems (See also Complexity Science) Systems characterized by complex, time-dependent behavior and interactions. Includes biological systems and complex man made systems such as the economy.
Effect Size A quantitative measure of the magnitude of the experimental effect between 2 groups groups. 
Efficacy The ability to produce a desired or intended result, often used to describe the effect  of a treatment within a clinical trial.  
Eggshell Skull Principle A legal doctrine that a defendant is liable for the plaintiff's unforeseen and uncommon reactions to the defendant's negligent or intentional act. 
Ego Dissolution A state often induced by psychedelics where the boundaries between the self and the external world become blurred. 
Electrophysiology The study of the electrical properties of biological cells and tissues. 
Emotion Socialisation The process by which parents influence their children's emotional development through their responses to their children's emotions. 
Emotional Breakthrough A sudden, profound emotional experience that can lead to significant personal insight and change. 
Empathogens A class of psychoactive drugs that produce experiences of emotional communion, oneness, relatedness, and emotional openness. Examples include MDMA. 
Empirical Evidence Information acquired by observation or experimentation that is used to validate or support a theory or treatment. 
Empiricism The theory that all knowledge is derived from sense-experience, emphasised in scientific methods and evidence-based practice. 
Entactogen Substances that enhance feelings of emotional openness and communication. 
Entheogen Substances that are used in a spiritual context, often to induce experiences perceived as connecting with a divine entity. 
Entropy (Neuroscience) A measure of unpredictability or complexity in the brain's activity patterns. 
Environmental Factors Aspects of the physical or social environment that can affect the outcome of therapy, such as the setting in which therapy is provided 
Epidemiology The study and analysis of the distribution (who, when, and where), patterns and determinants of health and disease conditions in defined populations. 
Epiphenomenon A secondary effect or byproduct that arises from but does not causally influence a process. 
Episodic Memory This is a type of declarative memory that involves personal experiences and specific events in time. For example, remembering your 18th birthday party.  
Equifinality The principle that a given end state can be reached by many potential means or pathways. 
Evidence-Based Models Therapeutic approaches that are backed by scientific research and clinical trials demonstrating their efficacy. 
Existential Confusion A state of deep uncertainty or questioning about the nature of existence and one's place in the world, often triggered by profound or disorienting experiences. 
Expectancy Bias The influence of participants' expectations on their response to treatment. 
Explanatory Levels Different levels of analysis for understanding mental health, such as genetic, neural, physiological, psychological, and social. 
Exposure Therapy A psychological treatment that helps a person  confront their fears by exposing them to the feared object or context within the bounds of a person’s tolerance. 
External Validity The extent to which the results of a study can be generalised to other settings, populations, and times. 
Externalising Disorders Mental disorders characterised by outward-directed behaviours, such as substance use issues and aggression. 
Extinction Learning The process through which a conditioned response decreases or disappears after repeated exposure to the conditioned stimulus without the unconditioned stimulus. 
False Memories Memories of events that never actually happened, which can be influenced by suggestion or other cognitive processes. 
Fidelity Rating Tools Instruments used to measure how closely a therapist adheres to a specific therapeutic model or protocol. 
Flooding An exposure therapy technique where the person is exposed to their feared object or context in an intense and prolonged manner. 
Functional Connectivity A measure of how brain regions co-activate or communicate with each other. 
Functional Impairment Limitations in performing certain tasks or activities due to psychological or physical conditions. 
Functional Unblinding The phenomenon whereby participants in a clinical trial deduce whether they are receiving the active treatment or placebo based on the effects they experience. 
Functional vs. Organic Distinction A classification in medicine distinguishing between conditions that have no clear physical cause (functional) and those that do (organic). 
Gabapentinoids A class of drugs, including gabapentin and pregabalin, used to treat neuropathic pain and seizures, and sometimes anxiety. 
General Paresis of the Insane A neuropsychiatric disorder affecting the brain, caused by untreated syphilis. 
General Systems Theory An interdisciplinary theory about the nature of systems in nature, society, and science. 
Generalizability The extent to which findings from a study can be applied to the wider population. 
Glutamate The most abundant neurotransmitter in the vertebrate nervous system, involved in cognitive functions like learning and memory. 
Hallucinations Perceptions in the absence of external stimuli that have qualities of real perception. 
Hallucinogen A diverse group of drugs that cause hallucinations. 
Healing vs. Treatment The distinction between holistic, often traditional practices aimed at overall well-being (healing) versus clinical interventions for specific conditions (treatment). 
Helicopter Money An monetary policy tool involving  the distribution of  sums of money to the public to stimulate the economy, or to groups to influence health
Hierarchical System A system in which elements are arranged in levels, with each level subordinate to the one above. 
Hierarchical Taxonomy of Psychopathology (HiTOP) An alternative framework for understanding mental disorders based on symptom dimensions rather than discrete categories. 
Hippocampus A brain structure involved in the formation, organisation, and storage of memories. 
Holotropic Breathwork A psychotherapeutic approach that uses deep, fast breathing and music to induce altered states of consciousness. 
Humanistic Models Therapeutic approaches that emphasise personal growth, self-actualization, and the individual's inherent potential for self-healing. 
Humoral Theory An ancient theory that health and illness result from a balance or imbalance of bodily fluids (humors): blood, phlegm, black bile, and yellow bile. Personalities thought to result from each of these humors were termed sanguine, phlegmatic, melancholic, and choleric respectively. 
Hypnagogic State The transitional state between wakefulness and sleep, often associated with vivid dreams and hallucinations. 
Hysteria An outdated medical term historically used to describe a a state of  excessive or uncontrollable emotion. In antiquity, believed to be a result of the womb travelling around the body. From the Greek for womb, ‘hystera’.
Ibogaine A naturally occurring psychoactive substance found in plants in the Apocynaceae family, known for its use in treating addiction. 
ICD (International Classification of Diseases) A global health information standard, similar to the DSM, for disease classification, produced by the World Health Organisation. 
Idealism The philosophical theory that reality is fundamentally mental, mentally constructed, or otherwise immaterial. 
Illusory Truth Effect The phenomenon where repeated statements are more likely to be perceived as true. 
In Silico Modeling Use of computer simulations to model biological and chemical processes. 
Indigenous Referring to the native people and their traditional practices, including in the context of using natural substances for healing. 
Individualism vs. Collectivism Cultural orientations that prioritise individual rights and independence versus group harmony and interdependence. 
Ineffable Incapable of being expressed in words; too great or extreme to be described in words. 
Informed Consent A process by which a patient agrees to a proposed medical treatment after fully understanding its risks, benefits, and alternatives. 
Integration Session A phase in psychedelic-assisted therapy where the patient works with the therapist to integrate and make sense of the experiences and insights gained during the psychedelic session. 
Integrative Models Approaches in psychotherapy that combine techniques and theories from multiple therapeutic traditions to best address the individual needs of the patient. 
Interferon A type of protein used in the treatment of viral infections and certain cancers, known to sometimes cause psychiatric side effects such as depression. 
Internal Validity The extent to which a study establishes a trustworthy cause-and-effect relationship between a treatment and an outcome. 
Internalising Disorders Mental health disorders characterised by inward-focused symptoms, such as depression and anxiety. 
Intuition / Inspiration / Revelation A way of knowing that involves understanding or gaining knowledge through immediate insight or direct perception without the use of rational processes. 
Iproniazid An antidepressant and anti-tuberculosis drug, one of the first to be used as an antidepressant. 
Ischemic Brain Injury Damage to the brain caused by a lack of blood supply, for example due to a stroke. 
Ketamine A dissociative anaesthetic drug that is also used in some therapeutic contexts for its rapid-acting antidepressant and/or psychedelic effects. 
Ketanserin A drug that blocks the  5-HT2A receptor antagonist, and thereby the psychedelic effects of psychedelic drugs.. 
Latent Disease Model A model that assumes an underlying disease causes symptoms, often implicit in medical classification systems. 
Learned Helplessness A state of a perceived lack of control over one's fate, often resulting from repeated exposure to uncontrollable negative events. 
LSD (Lysergic Acid Diethylamide) A synthetic chemical and classic psychedelic derived from ergot alkaloids, known for its psychological effects, which include altered thinking processes, closed- and open-eye visuals, synesthesia, an altered sense of time, and spiritual experiences. 
MAPS (Multidisciplinary Association for Psychedelic Studies) An organisation that conducts research and provides education about the potential uses of psychedelics in therapeutic settings. 
MDMA (Methylenedioxymethamphetamine) A psychoactive drug, sometimes termed an empathogen and often grouped with classic psychedelics under the term ‘psychedelic’. A popular recreational drug and a medication in phase III trials for the treatment of PTSD alongside psychotherapy. 
Melty Brain Problem A theoretical concern, coined by Johns Hopkins neuroscientist Gul Dolen, that increasing the brain's ability to change (plasticity) too much could lead to undesirable or chaotic outcomes. 
Mescaline A naturally occurring psychedelic alkaloid of the phenethylamine class, known for its hallucinogenic effects similar to those of LSD and psilocybin. 
Meta-Analysis A statistical analysis that combines the results of multiple scientific studies to identify patterns, discrepancies, or overall effects. 
Metacognition Awareness and understanding of one's own thought processes; thinking about thinking. 
Metacognitive Therapy A type of cognitive therapy that focuses on changing metacognitive beliefs about thinking and controlling thought processes. 
Methylone A synthetic stimulant similar to MDMA, in phase II research for the treatment of PTSD alongside psychotherapy.. 
Microbiome The collection of all the microorganisms living in association with the human body, which can influence health and disease. 
Microdosing The practice of taking sub-hallucinogenic doses of a psychedelic substance, often to improve mood, creativity, or cognitive function. 
MKUltra A code name given to an illegal program of experiments on human subjects that were designed and undertaken by the United States Central Intelligence Agency (CIA) intended to identify and develop drugs and procedures to be used in interrogations to weaken individuals and force confessions through brainwashing and psychological torture. 
Monoamine Theory A theory suggesting that the deficiency of certain neurotransmitters, such as serotonin, dopamine, and norepinephrine, is responsible for mental disorders like depression. 
Montgomery–Åsberg Depression Rating Scale (MADRS) A research measure used to evaluate the severity of depression symptoms. 
Mood Stabilizers Medications used to treat mood disorders characterised by intense and sustained mood shifts, such as bipolar disorder. 
Multifinality The principle that the same risk factor can lead to multiple different outcomes. 
Mystical Experience A state of consciousness characterised by a sense of unity with all existence, a feeling of sacredness, and an experience of profound truth. 
Naturalistic Study Research conducted in a real-world setting without manipulating variables. 
Neurobiological Mechanisms Biological processes and structures in the nervous system that contribute to the effects of psychedelics. 
Neuropathic Pain Pain caused by damage or disease affecting the somatosensory nervous system 
Neuroplasticity The brain's ability to reorganise itself by forming new neural connections throughout life. 
Neuropsychiatric Relating to mental disorders that are wholly or partly attributable  to diseases of the nervous system. 
Neurotransmitter Chemical messengers that transmit signals across a chemical synapse, such as from one neuron (nerve cell) to another 'target' neuron, muscle cell, or gland cell. 
NMDA  (N-methyl-D-aspartate) A glutamate receptor and ion channel protein found in nerve cells, crucial for controlling synaptic plasticity and memory function. 
Noetic Quality A characteristic of mystical experiences, referring to a sense of insight or knowledge that is felt to be deeply meaningful and true. 
Non-Directive Approach A type of therapy where the therapist follows the lead of the client without a guiding mechanistic framework. Distinct from ‘evidence-based therapies’.
Observational Study A study in which the researcher observes and records behaviour or outcomes without manipulating variables. 
Omniscience The state of knowing everything, often referred to in contexts where an individual feels an exaggerated sense of their own knowledge and power. 
Ontological Shock A profound disruption in one's beliefs or understanding of reality, often leading to existential questioning. 
Open-Label Extension A phase in a clinical trial where all participants receive the active treatment, and both the participants and researchers know which treatment is being administered. 
Open-Label Study A type of study in which both the researchers and participants know which treatment is being administered. 
Ordinary States of Consciousness Typical states of awareness experienced during normal waking hours.
Outcome Switching Changing the primary outcomes of a trial after the results are known. 
Panpsychism The view or belief that consciousness (mind or a mind-like aspect) is a fundamental and ubiquitous feature of reality. 
Patient Autonomy The right of patients to make decisions about their medical care without their health care provider trying to influence the decision. 
Pellagra A disease caused by niacin (vitamin B3) deficiency, characterised by diarrhoea, dermatitis, and dementia. Once a common cause of madness.
Perceptual Control Theory (PCT) A theory suggesting that mental ill-health  can be understood as the consequence of attempts to control one’s inner state. 
PET Imaging Positron Emission Tomography, a type of brain imaging technique used to observe metabolic processes. 
Phase I Trials Initial safety testing in a small group of healthy volunteers to determine safe dosage ranges and identify side effects. 
Phase II Trials Studies involving a larger group of patients to assess the drug's efficacy and further evaluate its safety. 
Phase III Trials Large-scale studies conducted to confirm efficacy, monitor side effects, and compare the drug to commonly used treatments. Typically required for regulatory approval. 
Phase IV Trials Post-marketing studies to delineate additional information including the drug's risks, benefits, and optimal use. 
Phenethylamine An organic compound that is a natural monoamine alkaloid, and acts as a central nervous system stimulant in humans. 
Phenomenology The philosophical study of the structures of experience and consciousness. 
Phenotypic Trajectory The observable characteristics or traits of an individual that can change over time. 
Placebo A substance or treatment with no active therapeutic effect, often used as a control in experiments to test the effectiveness of another substance or treatment. 
Placebo Effect A beneficial effect produced in the placebo arm of research. Distinct from the active effect of the treatment.. 
Placebo-Controlled Study A type of clinical trial in which a control group receives a placebo to compare against the effects of the actual drug or treatment. 
Plasticity The brain's ability to change and adapt 
Pluralistic Involving multiple methods or approaches, recognizing the diversity and complexity of a subject 
Polymerase Chain Reaction (PCR) A technique used to amplify small segments of DNA. 
Post-Marketing Surveillance Monitoring the safety and efficacy of a drug after it has been released on the market. 
Preclinical Research Laboratory and animal studies conducted to gather preliminary efficacy, toxicity, and pharmacokinetic information. 
Preparation, Dosing, and Integration Phases of psychedelic therapy involving preparation, administration of the substance, and subsequent integration of the experience into daily life. 
Procedural Memory This type of memory involves skills and how to perform tasks. It’s also known as implicit memory because you don’t have to consciously think about how to perform these tasks once they are learned. For example, riding a bike or playing the piano. 
Psilocybin A naturally occurring psychedelic compound produced by certain species of mushrooms, often referred to as "magic mushrooms". 
Psychoactive Substances that affect the mind, mood, or behavior. 
Psychoanalysis A set of psychological and psychotherapeutic theories and associated techniques, originally popularised by Sigmund Freud, which proposes that mental ill-health is a consequence of unconscious conflict. 
Psycho-Contextual Mechanisms Psychological and contextual factors and processes that contribute to the therapeutic effects of any treatment, including therapy and psychedelic treatments. 
Psychodynamic Therapy A form of therapy deriving from psychoanalysis, focusing on unconscious processes as they are manifested in a person’s present behaviour. 
Psychoeducation The process of educating patients about their mental health and the therapeutic strategies used to treat ill-health. 
Psycholytic Therapy A form of psychotherapy that uses low doses of psychedelic drugs to assist psychoanalytic psychotherapy. 
Psychonauts Individuals who use psychedelics to explore altered states of consciousness. 
Psychosis A  mental disorder characterised by a disconnection from reality, often including delusions and hallucinations. 
PTSD (Post-Traumatic Stress Disorder) A mental health condition triggered by experiencing or witnessing a traumatic event. 
p-value A statistical measure that helps determine the significance of research results. A p-value of less 0.05 is typically taken to mean statistically significant and means that there is less that a 1 in 20 chance that the results are by chance
Pyramidal Cells A type of excitatory neuron in the brain that plays a key role in cognitive functions. 
QT Interval A measurement made on an electrocardiogram (ECG) used to assess some of the electrical properties of the heart; prolonged QT interval can lead to dangerous arrhythmias. 
Randomised Control Trials (RCTs) A scientific study design that randomly assigns participants into an experimental group or a control group to ensure that any observed effects are due to the intervention. 
Rationalism A theory that opinions and actions should be based on reason and knowledge rather than on religious belief or emotional response. 
Real-World Effectiveness The performance of a drug in the general population under real-world conditions, outside the controlled environment of clinical trials. 
REBUS Model A model proposing that psychedelics ‘relax beliefs’, allowing for a more flexible state of mind. 
Receptor A protein molecule that receives and responds to a neurotransmitter, hormone, or other substance. 
Receptor Occupancy The extent to which a drug occupies its target receptors in the brain. 
Reciprocity An ethical principle emphasising mutual respect and acknowledgment of the contributions of different communities, especially those that have traditionally used psychedelic substances. 
Reductionism The approach of reducing complex systems to simpler components that are more manageable to study. In the context of mental health reductionism tends to give rise to silos and simplistic explanatory models
Regression to the Mean The phenomenon whereby if a variable is extreme on its first measurement, it will tend to be closer to the average on its second measurement. 
Regulatory Review Process The process by which regulatory authorities review study data and decide whether to grant approval for a drug. 
Reification The process of making something real, bringing something into being, or making something concrete. May be used to refer to the inappropriate continued use of a once-useful mental shortcut.
REM Sleep Rapid Eye Movement sleep, a stage of sleep characterised by vivid dreams and increased brain activity. 
Research Domain Criteria (RDoC) A research framework for studying mental disorders developed by the National Institute of Mental Health, focusing on dimensions of observable behaviour and neurobiological measures. 
Resting State A condition in which a person is awake but not engaged in any specific mental task, often used in neuroimaging studies. 
Resting State Functional Connectivity Brain activity measured when a person is not performing any specific task. 
Retrograde Facilitation The phenomenon where substances like alcohol can enhance the memory of events that occurred just before consumption. 
Rumination Repetitive and passive focus on one's symptoms of distress and its possible causes and consequences. An important causal component of many mental disorders
Rupture and Repair Cycle A process in therapy where a breakdown in the therapeutic alliance occurs (rupture) and is subsequently resolved (repair), which may strengthen the relationship. 
Safeguarding Measures taken to protect the health, well-being, and rights of patients in a therapeutic setting. 
Safety-Seeking Behaviour Actions taken to avoid perceived threats, often seen in anxiety disorders. 
Schema Therapy A form of psychotherapy that combines elements of cognitive-behavioural therapy, psychoanalysis, and other techniques to treat chronic mental health issues. 
Scientist Practitioner A therapist who uses scientific methods to inform their practice, reflecting on their actions during therapy sessions and seeking continuous learning and improvement. 
Screening The process of evaluating potential patients to determine their suitability for a particular treatment or clinical trial 
Selection Bias The bias introduced by selecting non-random data for analysis, leading to conclusions that may not be generalizable. 
Selection Criteria The criteria by which participants are selected for inclusion in a study. 
Self-Disclosure A therapist's sharing of personal information with a patient, which can help build trust and rapport but must be managed carefully to maintain professional boundaries. 
Self-Efficacy The belief in one's own ability to succeed in specific situations or accomplish a task. 
Self-Referential Processing Cognitive processes that involve thinking about oneself, such as introspection or self-evaluation. 
Self-Transcendence The experience of moving beyond one's own immediate concerns and gaining a broader perspective that includes a connection to others or the universe. 
Semantic Memory A type of declarative memory that involves general knowledge and facts about the world. For example, knowing that Paris is the capital of France.  
Semantic Priming The process by which exposure to one word can facilitate the recognition or recall of related words. 
Serotonin (5HT, 5-Hydroxytryptamine) A monoamine neurotransmitter that is believed to contribute to feelings of well-being and happiness. 
Serotonin 2A (5HT-2A) Receptors The main  receptor in the brain that binds classic psychedelics. 
Serotonin Syndrome A potentially life-threatening condition caused by an excess of serotonin in the brain, often due to drug interactions. 
Set and Setting Refers to the mindset (set) and the physical and social environment (setting) in which one takes a psychedelic drug, which can significantly influence the experience. 
Shaman A person regarded as having access to, and influence in, the world of spirits, typically involving practices of healing and divination. 
Sigma-1 Receptor A receptor involved in several functions, including neuroprotection and modulation of ion channels. 
Social Determinants of Health Conditions in the environments where people are born, live, learn, work, play, and age that affect health outcomes and risks. 
Socioeconomic Factors Social and economic factors that can influence health outcomes and access to healthcare. 
Socioeconomic Status The social standing or class of an individual or group, often measured as a combination of education, income, and occupation. 
Somatic Relating to the body, especially as distinct from the mind. 
Somatic Therapy A holistic therapy that studies the relationship between the mind and body. 
Spandrels Originally an architectural term, used in biology to refer to byproducts of adaptation that were not directly selected for but emerged as side effects of other evolutionary changes. 
Spiritual Emergency A crisis during which a person's growth and consciousness development become challenging and difficult to manage, potentially leading to psychological distress. 
SSRI (Selective Serotonin Reuptake Inhibitor) A class of drugs typically used as antidepressants in the treatment of major depressive disorder, anxiety disorders, and other physical and mental conditions. 
Standardized Mean Difference (SMD) A summary statistic used in meta-analyses to measure the effect size across studies. 
Statins Medications used to lower cholesterol levels in the blood. 
Statistical Conclusion Validity The degree to which conclusions about the relationship among variables based on the data are correct or reasonable. 
Stimulants Drugs such as amphetamine, often prescribed for Attention Deficit Hyperactivity Disorder (ADHD). 
Stoic Philosophy An ancient Greek philosophy that teaches the development of self-control and fortitude as a means to overcome destructive emotions. 
Structural Equation Modelling A statistical technique used to test and estimate causal relationships using a combination of statistical data and qualitative causal assumptions. 
Sub Perceptual Doses of a drug that are too small to produce noticeable effects. 
Suggestibility The degree to which a person is inclined to accept and act on suggestions by others. 
Supershrinks Term used to describe therapists who achieve significantly better outcomes compared to their peers. 
Sympathomimetic A drug or other substance that mimics the effects of the sympathetic nervous system (e.g., increased heart rate and blood pressure). 
Synergy The interaction or cooperation of two or more treatments or interventions to produce a combined effect greater than the sum of their separate effects. 
Synesthesia A condition in which a stimulus in one modality is  perceived by a sense of a different modality, for example tasting music.
Systematic Review A type of literature review that collects and critically analyzes multiple research studies or papers. 
Systemic Problems Issues that arise from the interactions within and between systems, such as family dynamics or social environments, rather than from an individual alone 
Task Shifting The process of training non-specialist community members to deliver mental health interventions, often used in low-resource settings. For example The Friendship Bench in Zimbabwe.
Temperament The inherent traits that influence how individuals think, behave, and relate, often used interchangeably with  personality. 
Thalamus A brain structure that acts as a relay station for sensory and motor signals to the cerebral cortex. 
Therapeutic Alliance, or Therapeutic Relationship The collaborative and trusting relationship between a therapist and a patient, considered crucial for effective therapy. 
Therapeutic Dyad A pair of therapists (often male and female) working together with a single patient. 
Therapeutic Touch The use of touch by a therapist to support and comfort patients, which must be consensual and appropriate to the therapeutic context. 
Therapist Effects The impact that individual therapists have on therapy outcomes, beyond the specific type of therapy they provide. 
Third-Wave Cognitive Behavioural Therapies The most recent development in CBT, incorporating mindfulness and acceptance strategies, such as Acceptance and Commitment Therapy (ACT) and Mindfulness-Based Cognitive Therapy (MBCT). 
Tolerability The degree to which overt adverse effects of a drug can be tolerated by a patient. 
Top-Down Processing Cognitive processing  driven by expectations or prior knowledge, rather than by e.g. perception.. 
Transcendental State An altered state of consciousness characterised by a sense of unity with the universe, often experienced during deep meditation or under the influence of psychedelics. 
Transcranial Direct Current Stimulation (tDCS) A form of neurostimulation that uses constant, low current applied directly or indirectly to the brain.. 
Transcranial Magnetic Stimulation (TMS) A non-invasive treatment for depression and other conditions  that uses magnetic fields applied to the brain.. 
Transdiagnostic Factors or Mechanisms Causal or risk factors  that are relevant across multiple diagnostic categories, rather than being specific to one condition. 
Transdiagnostic Treatments Treatments that are applicable across multiple different diagnostic groups, rather than being specific to one disorder. 
Transference In psychoanalysis, the idea that a patients behaviour and emotional responses to the therapist are a redirection of a theirfeelings for a significant other. 
Translational Science The process of turning basic scientific discoveries into practical applications, such as treatments or therapies, that improve patient health. 
Transpersonal Relating to experiences that transcend the usual personal identity or sense of self, often involving a spiritual dimension. 
Trephination An ancient medical intervention in which a hole is drilled into the human skull. 
TRKB (Tropomyosin Receptor Kinase B) A receptor for BDNF that plays a key role in neuroplasticity. 
Tryptamine A monoamine alkaloid widely distributed in plants, animals, and fungi, and plays a role in various physiological functions. 
Vagal Nerve Stimulation (VNS) A treatment involving electrical stimulation of the vagus nerve to treat epilepsy and depression. 
Vicious Cycles Negative reinforcing feedback loops wherein a problem exacerbates itself.