N, N-Dimethyltryptamine (DMT)-Occasioned Familiarity and the Sense of Familiarity Questionnaire (SOF-Q)

Data were drawn from a prior mixed-methods qualitative analysis of inhaled-DMT reports posted to the Reddit r/DMT community between 2009 and 2018. The larger project involved manually screening the titles of 30,652 posts and reviewing full posts to compile a final dataset of 3,778 unique inhaled-DMT experiences. From that corpus, the present study focused on the 227 unique experiences that had been coded as including a "sense of familiarity"; 56 of these (24.7%) were from users reporting this as their first DMT experience (classified here as DMT-naïve). An inductive grounded-theory style qualitative analysis was performed on the 227 reports. A single experienced reviewer identified meaningful units (MUs) related to familiarity, which were organised into categorical themes and refined through coauthor consensus. In addition to the inductive coding, the researchers documented co-occurrence with established measures and constructs where possible, specifically items from the Mystical Experience Questionnaire (MEQ), the Ego Dissolution Inventory (EDI), and a binary marker for a "profound experience of death." The methods text notes that detailed decisions about latent class model form, number of classes and prior choices are provided in supplemental materials. From the qualitative coding, the team derived 19 binary SOF-Q items clustered into five thematic categories: (1) Familiarity with the Feeling, Emotion, or Knowledge Gained; (2) Familiarity with the Place, Space, State, or Environment; (3) Familiarity with the Act of Going Through the Experience; (4) Familiarity with Transcendent Features; and (5) Familiarity Imparted by an Entity Encounter. Presence/absence of each SOF-Q item was recorded for all 227 experiences. To explore whether respondents formed distinct subgroups of familiarity profiles, the investigators applied an exploratory Bayesian latent class analysis to the 19 binary items. Models were fit using Hamiltonian Monte Carlo in Stan called from R, with plots generated via ggplot2 and tidybayes; model diagnostics and selection rationale are reported as supplemental. The study had institutional research ethics board approval (University of Toronto REB protocol number 39101). Data and code are reported as publicly available on a GitHub repository.

The analytic sample comprised 227 unique inhaled-DMT experiences coded as containing a sense of familiarity; 56 (24.7%) were from DMT-naïve users. Importantly, none of the 227 reports explicitly attributed the familiarity to a prior DMT or other psychedelic experience. A high proportion of these familiarity-tagged experiences also contained features discordant from ordinary consciousness. Specifically, 221 experiences (97.4%) included at least one MEQ item. Breakdown by MEQ subdomain was: mystical items in 162 experiences (71.4%), positive mood items in 217 (95.6%), transcendence of space/time items in 215 (94.7%), and ineffability items in 63 (27.8%). Elements of ego-dissolution were present in 37 experiences (16.3%), and 25 experiences (11.0%) included a "profound experience of death." Similar rates were reported within the DMT-naïve subset. The inductive SOF-Q coding produced item-level prevalences across the five thematic categories. Within "Familiarity with the Feeling, Emotion, or Knowledge Gained," the core item "sense of familiarity" was endorsed in 201 reports (88.5%). Other items in that category were: "feels like home or going home" 51 (22.5%), "sense of comfort" 43 (18.9%), "sense of remembering something…you may have forgotten" 33 (14.5%), "sense of welcoming" 32 (14.1%), "sense of belonging" 24 (10.6%) and "sense of nostalgia" 5 (2.2%). For "Familiarity with the Place, Space, State, or Environment," an "intuitive sense that you are returning to a place…you have been before" appeared in 58 reports (25.6%) and an "intuitive sense that you will return…again" in 17 (7.5%). Items in the "Act of Going Through the Experience" grouping included "sense of déjà vu" 18 (7.9%), "feels like you have gone through this experience before" 17 (7.5%), "feels like you have done this many times before" 11 (4.8%), and "feels like you will go through this experience again" 6 (2.6%). Under "Familiarity with Transcendent Features," items endorsed were: visited a place that exists preconception or after death 15 (6.6%), experienced a place that is eternal or infinite 11 (4.8%), and experienced a place or state where your consciousness resides 9 (4.0%). For "Familiarity Imparted by an Entity Encounter," the prevalences were: encountered an entity or presence that knew you or expressed a familiarity or bond with you 52 (22.9%), encountered an entity you felt familiar with or had a bond with 46 (20.3%), and encountered an entity that felt like your family 26 (11.5%). The Bayesian latent class analysis identified two stable classes. Most participants (mean 76%; 90% compatibility interval 68% to 83%) belonged to Class 2, while about one quarter (mean 24%; 90% CI 17% to 32%) belonged to Class 1. Both classes showed similar endorsement patterns for items about place, the act of going through the experience, and transcendent features. However, Class 1 had substantially higher probabilities of endorsing items in the "Familiarity Imparted by an Entity Encounter" and "Familiarity with the Feeling, Emotion, or Knowledge Gained" categories. For example, the probability of endorsing "encountered an entity…you knew, felt familiar with, or have an established bond with" was estimated at 55.2% in Class 1 versus 9.8% in Class 2; "encountered an entity or presence that knew you or expressed a familiarity or bond with you" was 82.6% in Class 1 versus 4.5% in Class 2; and "encountered an entity…that felt like your family" was 48.4% in Class 1 versus 0.7% in Class 2. Within the feeling/emotion category, an estimated 46.3% of Class 1 members endorsed "felt a sense of comfort" compared with 4.5% in Class 2. Conversely, the prototypical core item "sense of familiarity" had an estimated endorsement of 94.2% in Class 2 versus 68% in Class 1. The paper includes illustrative participant quotations organised by SOF-Q theme; these quotes were used to support theme formation but prevalence counts and model estimates above reflect the coded binary items.

Lawrence and colleagues interpret their findings as indicating that the sense of familiarity reported during inhaled-DMT experiences is not referential to a prior DMT or psychedelic session, given that no reports explicitly identified a previous psychedelic exposure as the source and some DMT-naïve users nevertheless described marked familiarity. Familiarity commonly co-occurred with features of non-ordinary consciousness, such as mystical experiences, transcendence of space and time, ineffability, ego-dissolution and, occasionally, experiences framed as death. This pattern suggests the reported familiarity often arises within experiences that are phenomenologically distant from ordinary waking states. To facilitate future work the investigators developed the 19-item Sense of Familiarity Questionnaire (SOF-Q) organised into five thematic categories, and they propose a 6-point Likert version for more graded measurement. The authors explicitly state that the SOF-Q requires formal psychometric validation before use in research or clinical settings. They also acknowledge study limitations that bear on interpretation: the sample was self-selected from an online forum, which introduces selection and sample bias; dosing, set and setting, and enduring outcomes were not captured; coding was performed by a single rater which risks single-rater bias; and the SOF-Q was not subjected to reliability or factor-structure testing in this report. The discussion situates the phenomenological findings within emerging ideas about recognition memory and the neural effects of psychedelics. Familiarity is contrasted with recollection in recognition memory theory, and the phenomenon observed here is likened to "familiarity without recollection," analogous to clinical examples such as the "butcher-on-the-bus" effect. The authors review neural models relevant to DMT: DMT reduces alpha power, alters travelling-wave dynamics that diminish top-down signalling while increasing bottom-up flow, and modulates default mode network connectivity including medial temporal lobe regions implicated in memory. Within the REBUS and anarchic brain frameworks, psychedelics engender a more entropic, globally flexible brain state; Carhart-Harris and Friston's account is cited to suggest that subjective familiarity may emerge as the acute psychedelic state subsides and the brain re-enters its prior regime. Two broad etiological possibilities for DMT-occasioned familiarity are outlined. The "nonveridical" hypothesis views the familiarity as a drug-induced misattribution or epiphenomenon due to altered neural processing of familiarity signals. The "veridical" hypothesis posits that familiarity reflects genuine prior encounters, which could relate to autobiographical recall, endogenous DMT-mediated states, or previous global states of consciousness. The present results exclude prior exogenous psychedelic sessions as a common veridical source but do not adjudicate between other veridical or nonveridical accounts. The authors therefore call for further empirical research—comparative phenomenology, psychometric validation of the SOF-Q, and neuroscientific studies—to clarify mechanisms and implications for both basic science and potential therapeutic contexts.

This study documents and characterises features of a sense of familiarity reported in a subset of naturalistic inhaled-DMT experiences and presents the Sense of Familiarity Questionnaire (SOF-Q), a 19-item instrument organised into five thematic categories designed to capture these features. The familiarity described by participants did not appear to reference prior DMT or psychedelic use, and it frequently co-occurred with phenomenologically unusual experiences such as mysticism, ego-dissolution and experiences framed as death. The SOF-Q is offered as a preliminary tool to support further investigation, but requires formal psychometric evaluation before broader application. The authors suggest that understanding this phenomenon may inform basic research into altered states of consciousness and could have implications for psychedelic-assisted therapeutic practice.