Drug-induced social connection: both MDMA and methamphetamine increase feelings of connectedness during controlled dyadic conversations

The study investigates how MDMA, known for its prosocial and empathogenic effects, alters real-life social interactions, specifically feelings of connectedness during face-to-face conversations. Although MDMA has been reported to increase sociability in humans and prosocial behaviors in animals, few controlled studies have tested its effects during actual interpersonal interactions or examined pharmacological specificity and physiological mechanisms. The authors hypothesized that MDMA would enhance connectedness with an unfamiliar partner during a semi-structured conversation and explored whether a prototypical stimulant, methamphetamine (MA), would show similar effects. The work aims to clarify behavioral processes underlying drug-facilitated social connection and to probe the role of oxytocin as a potential physiological mediator.

Prior work shows MDMA increases sociability, time spent interacting, and alters socioemotional processing in ways likely to impact social function (e.g., facial emotion processing, empathy, trust). Animal studies indicate increased social approach after MDMA. Clinical and qualitative reports suggest enhanced interpersonal trust and empathy in MDMA-assisted therapy and recreational use contexts. Prototypic stimulants (e.g., amphetamine) increase talkativeness and social feelings but are not typically associated with increased closeness. Oxytocin has been implicated in MDMA’s prosocial effects, with mixed evidence linking peripheral oxytocin to subjective empathy; MA generally shows weaker effects on oxytocin. Few prior studies tested drug effects during real dyadic interactions under double-blind conditions, motivating the present in-person conversation paradigm.

Design: Two separate, double-blind, within-subject, randomized-order crossover studies with healthy adults. Study 1 (MDMA; N=18) tested 100 mg MDMA vs placebo; Study 2 (MA; N=19) tested 20 mg methamphetamine vs placebo. Each participant completed two 4.5-hour laboratory sessions (drug and placebo), separated by ≥4 days (Study 1) or ≥3 days (Study 2). Participants: Healthy volunteers aged 18–35, BMI 19–30, English fluent, high-school completion, low-to-moderate daily alcohol/caffeine. Exclusions included medical conditions, abnormal EKG, current DSM-5 substance dependence or major psychiatric disorders, treatment for SUDs, pregnancy. Study 1 required lifetime MDMA use (1–40 times) without adverse effects. Screening included physical exam, EKG, psychiatric interview, drug use history, and SCL-90R. Blinding/expectancies: Participants informed capsules might contain placebo, stimulant (e.g., amphetamine or MDMA), sedative, or hallucinogen to minimize drug-specific expectancies. Pre-session abstinence from drugs/alcohol verified by urine and breath testing; pregnancy tests for women. Drug administration: Study 1: 100 mg MDMA (powder in opaque capsule with lactose). Study 2: 20 mg MA (four 5 mg Desoxyn tablets encapsulated with dextrose). Placebo matched filler. Procedure: Sessions ran 9:00–13:30. Baseline mood and cardiovascular measures were taken pre-dose (09:00). Drug/placebo ingested at 09:30. At 10:40, participants engaged in a 45-min semi-structured conversation with a novel, same-sex partner trained to interact naturally and blind to drug condition. Conversation topics (“small talk”) changed every 15 minutes. Subjective and cardiovascular measures were collected at 30, 60, 120, 180, and 210 min post-dose. A single saliva sample for oxytocin was collected at 120 min (after 1 h of no eating and 10 min no drinking). End-of-session ratings of connectedness and partner closeness were completed. One week after the second session, participants completed online follow-up ratings of conversations and partners. Measures:

• Subjective drug effects: Drug Effects Questionnaire (DEQ; feel, like/dislike, high, want more), Visual Analog Scales (VAS; adjectives including anxious, stimulated, insightful, sociable, confident, lonely, playful, loving, friendly, restless, trusting, appreciated, grateful, understood, loved), Profile of Mood States (POMS; 8 subscales).
• Physiological: Blood pressure and heart rate at repeated time points.
• Hormonal: Salivary oxytocin at 120 min using Phoenix Pharmaceuticals RIA after solid-phase extraction (LOD 0.313 pg/mL; intra-assay CV 4.06–5.85%; inter-assay CV 7.89–12.8%).
• Social connection outcomes (primary): Conversation Questionnaire (6 items; 0–9) and Inclusion of Other in Self (IOS; 1–7 overlapping circles) at end of session and at 1-week follow-up; Connection During Conversations Scale (CDCS; 16 items; 1–7; subscales: shared reality, partner responsiveness, participant interest, affective experience) at end of session. End-of-session drug-guessing questionnaire. Data analysis: Studies analyzed separately. Primary outcomes were individual items on conversation rating questionnaires at end of session; mixed-model ANOVAs with within-subject factor drug (drug vs placebo), and between-subject factors sex and order (drug-placebo vs placebo-drug). Repeated-measures subjective and cardiovascular outcomes analyzed as peak change from baseline using paired t-tests. Pearson correlations assessed relationships between oxytocin (drug minus placebo) and closeness ratings (drug minus placebo) and between oxytocin and heart rate. Alpha set at p < 0.05.

Sample and exclusions: Two participants excluded from Study 1 analyses (one due to strong negative feelings toward partner; one socialized with partner before follow-up). Most participants were in their 20s with at least some college; Study 1 had higher lifetime drug use per inclusion criteria. End-of-session connection (primary outcomes):

• Study 1 (MDMA; N≈17): Compared to placebo, MDMA increased liking the partner (F1,13=8.2, p=0.01, ηp2=0.39), conversation enjoyment (F1,13=7.1, p=0.02, ηp2=0.36), and meaningfulness (F1,13=8.9, p=0.01, ηp2=0.41). IOS showed a trend toward greater connection (F1,13=4.7, p=0.05, ηp2=0.27). On CDCS, MDMA increased ratings that partner was interested in participant’s thoughts/feelings (F1,13=7.7, p=0.02), understood who I am (F1,13=5.1, p=0.04), cared about me (F1,13=8.9, p=0.01), respected my beliefs/opinions (F1,13=5.4, p=0.04), and that participant was interested in partner’s thoughts/feelings (F1,13=6.1, p=0.03). Subscales: higher partner responsiveness (F1,13=15.4, p=0.002, ηp2=0.54) and participant interest (F1,13=5.4, p=0.04, ηp2=0.30).
• Study 2 (MA; N=19): MA increased enjoyment (F1,15=13.8, p=0.002, ηp2=0.48), meaningfulness (F1,15=6.3, p=0.02, ηp2=0.30), liking partner (F1,15=15.2, p=0.001, ηp2=0.50; drug×order p=0.01), perceived that partner liked them (F1,15=9.1, p=0.009; drug×order p=0.04), and closeness to partner (F1,15=10.9, p=0.005, ηp2=0.42). IOS increased (F1,15=8.6, p=0.01, ηp2=0.36). CDCS: higher “in sync” (F1,15=9.1, p=0.009; drug×order p=0.04), “they cared about me” (F1,15=6.8, p=0.02), participant interest in partner’s thoughts/feelings (F1,15=10.7, p=0.005), and attentiveness (F1,15=4.8, p=0.045). Lower negative items: “they were boring” (F1,15=14.7, p=0.002), “hard to communicate” (F1,15=17.3, p=0.001; interactions present), “couldn’t wait to end” (F1,15=19.4, p=0.001), and “energy drained” (F1,15=5.6, p=0.03). Subscales: increases in shared reality (F1,15=7.2, p=0.02), partner responsiveness (F1,15=6.7, p=0.02), participant interest (F1,15=17.2, p=0.001), and affective experience (F1,15=18.5, p=0.001). Follow-up (1 week):
• Study 1 (MDMA): Conversation after MDMA rated more meaningful than after placebo (F1,12=5.8, p=0.03); partners rated more physically attractive (F1,12=5.5, p=0.04) and warm (F1,12=5.1, p=0.04; drug×order p=0.02). Perceived by partners as less competent (F1,12=10.0, p=0.008; interactions present) and more warm (F1,12=9.6, p=0.009). No significant difference in desire for another conversation; IOS closeness not significantly higher.
• Study 2 (MA): Higher enjoyment (F1,15=22.6, p=0.0003; drug×order p=0.03) and meaningfulness (F1,12=12.9, p=0.003); greater liking (F1,15=8.6, p=0.01; drug×order p=0.01), closeness (F1,12=12.0, p=0.003), and more in common (F1,15=6.9, p=0.02; higher-order interaction present). Partners rated warmer (F1,15=5.5, p=0.04). Participants reported partners perceived them as more intelligent (F1,15=10.0, p=0.006), kind (F1,15=5.2, p=0.04), and warm (F1,15=13.8, p=0.002). Greater desire to converse again (F1,15=9.0, p=0.009). IOS not significantly different. Subjective drug effects and mood: Both drugs increased DEQ items (feel drug, like drug, dislike drug, high, want more). VAS: both increased stimulated, insightful, sociable, loving, friendly; only MDMA increased trusting, appreciated, grateful, loved; only MA increased understood. POMS: both increased elation, friendliness, vigor; only MDMA increased anxiety and confusion; only MA decreased fatigue. Physiology and hormones: Both drugs increased systolic/diastolic BP and heart rate. Both increased mean salivary oxytocin vs placebo, but many samples, especially placebo, were below LOD (recorded as 0.313 pg/mL). Oxytocin-closeness correlation was significant for MDMA (p=0.03) but not for MA (p=0.8). Oxytocin did not correlate with heart rate for either drug. Drug identification: Study 1—34% correctly identified placebo; 75% correctly identified MDMA as stimulant. Study 2—74% correctly identified placebo; 74% correctly identified MA as stimulant.

The findings confirm the hypothesis that MDMA enhances feelings of connectedness during real-life, in-person dyadic conversations, extending prior laboratory and anecdotal evidence to a socially relevant context under double-blind conditions. Unexpectedly, methamphetamine produced similar increases in connectedness, enjoyment, and perceived partner warmth, suggesting that some aspects of social connection in this paradigm may be driven by stimulant effects, potentially via increased talkativeness, attentiveness, or positive affect that facilitate disclosure and rapport. The positive association between oxytocin and closeness after MDMA, but not after MA, supports partial pharmacological specificity: MDMA’s serotonergic actions may elevate oxytocin and contribute to perceived closeness, whereas MA’s dopaminergic/noradrenergic actions may enhance attentiveness and reduce negative interaction qualities, yielding connectedness through different mechanisms. The persistence of enhanced meaningfulness (and multiple partner evaluations for MA) at one week suggests that drug-facilitated social interactions can have enduring subjective impact. These results have implications for psychotherapy, where increased patient-therapist connectedness might facilitate therapeutic processes, and raise the possibility that drugs other than MDMA could modulate therapeutic alliance under controlled conditions.

Both MDMA (100 mg) and methamphetamine (20 mg), relative to placebo, increased perceived connectedness, liking, and the meaningfulness/enjoyment of semi-structured conversations with unfamiliar partners. MDMA uniquely showed a relationship between elevated salivary oxytocin and closeness ratings, indicating a potential role of oxytocinergic mechanisms, while MA’s effects may reflect enhanced attentiveness and reduced negative interaction qualities. The study introduces a sensitive, ecologically valid paradigm to quantify drug-induced social connection and suggests broader implications for adjunctive pharmacotherapy in psychotherapy. Future work should directly compare drugs and doses within a single study, incorporate richer behavioral and linguistic analyses of conversations, examine different social contexts (e.g., shallow vs deep topics, therapist-patient interactions), and employ more sensitive and repeated measures of oxytocin and other biomarkers to clarify mechanisms.

• The two studies (MDMA and MA) were conducted in separate samples; no direct head-to-head comparison within the same participants and only a single dose per drug.
• Study 1 required prior MDMA experience, whereas Study 2 participants generally had little to no MDMA history; effects of prior drug use on outcomes are uncertain.
• Salivary oxytocin assay sensitivity was limited; many placebo (and some drug) samples were below detection and coded at the assay’s lower limit, potentially biasing estimates. Only one post-dose sample was collected without a baseline; oxytocin shows day-to-day variability.
• Primary outcomes were self-report; although validated, other connectedness constructs (e.g., broader connectedness scales) were not assessed.
• Conversations were not analyzed behaviorally (e.g., speech content/quality not reported), limiting insight into mechanisms (quantity/quality of communication vs affective connectedness).
• Small sample sizes reduce power and generalizability.