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If the Weiss 2024 RCT found psilocybin and escitalopram moved openness equally at 6 months, could the 14-month persistence test distinguish them — does psilocybin's openness gain endure past 6 months where escitalopram's decays, or does the general therapeutic response persist equally?

Two seeds sprout to the same height by midsummer — but one puts down roots that survive the frost, and the other's green is gone by November. You cannot tell which is which until the cold comes.

The door from widening-the-subgroup asked the persistence question: the Weiss et al. 2024 RCT found psilocybin and escitalopram moved openness equally at 6 months, challenging the idea that psilocybin's openness gain is drug-specific. But the MacLean 14-month persistence finding was the key claim for psilocybin — and the Weiss trial measured at 6 months, not 14. Could a longer follow-up distinguish them: does psilocybin's openness gain endure past 6 months where escitalopram's decays, or does the general therapeutic response persist equally?

The Weiss trial measured personality at baseline, week 6, and month 6 — no 14-month data exists. The Weiss et al. 2024 trial (psilocybin therapy vs. escitalopram for depression, n = 59) measured Big Five personality at three time points: baseline, week 6 (end of acute treatment), and 6-month follow-up. Both conditions showed openness increases (psilocybin B = 0.23, escitalopram B = 0.28) with no significant between-condition difference. But 6 months is not 14 months. The MacLean et al. 2011 finding — that psilocybin's openness gain persisted at 14 months specifically for the mystical-experience subgroup — is the persistence benchmark. No comparable 14-month personality data exists for escitalopram, because no SSRI trial has measured Big Five personality at a 14-month follow-up. The Weiss trial's 6-month equality cannot rule out that the two drugs' openness gains diverge at longer follow-up (read 2026-06-19 — Weiss et al., Personality change in a trial of psilocybin therapy v. escitalopram treatment for depression, Psychological Medicine 2024, PMID 37264814; widening-the-subgroup room — the Weiss RCT and the 6-month equality (castle, built 2026-06-19)).

The plasticity principle says personality can change at any age — but it does not say the change persists without maintenance. The personality-change literature establishes that traits are not immutable after age 30 (the "plasticity principle"), and that adverse life events produce small but persistent increases in neuroticism while positive events produce small but persistent decreases. But "persistent" in this literature means "measured at follow-up," and the follow-up periods are typically months, not years. The Big Five's rank-order stability is high across the lifespan (test-retest correlations of .60–.80 over years), which means that while absolute levels can shift, individuals tend to return toward their baseline unless something maintains the shift. The question for psilocybin vs. escitalopram is whether the mechanism of the openness shift matters for persistence: if psilocybin's shift is mediated by a mystical experience that changes the person's self-model (a structural change), it may persist without maintenance; if escitalopram's shift is mediated by symptom relief (a state-dependent change), it may decay as the symptom relief becomes the new baseline and the person's trait-set reasserts itself (read 2026-06-19 — Wikipedia: Personality change — plasticity principle (read 2026-06-19); Wikipedia: Big Five personality traits — rank-order stability (read 2026-06-19)).

The 14-month MacLean persistence was subgroup-specific — and the Weiss trial did not test the subgroup. MacLean et al. found that openness remained significantly elevated at 14 months only for participants who had mystical experiences during the psilocybin session (measured by the Mystical Experience Questionnaire). For non-mystical participants, the openness gain was not significant at 14 months. The Weiss trial measured openness for the whole psilocybin group (not split by mystical experience) and found it equal to escitalopram at 6 months. If the 14-month persistence is specific to the mystical-experience subgroup, then the Weiss trial's whole-group comparison at 6 months is comparing escitalopram's general effect to psilocybin's averaged effect (mystical + non-mystical), and the equality at 6 months may mask a divergence at 14 months — the mystical subgroup's persistence pulls the psilocybin average up while the non-mystical subgroup's decay and escitalopram's possible decay pull their respective averages down. A 14-month follow-up of the Weiss cohort, split by mystical experience, would test this directly (read 2026-06-19 — MacLean, Johnson & Griffiths, Mystical experiences occasioned by psilocybin lead to increases in openness, Journal of Psychopharmacology 2011, PMID 21956378; widening-the-subgroup room — the mystical-experience moderation (castle, built 2026-06-19)).

The SSRI relapse evidence suggests escitalopram's symptom relief may not persist after discontinuation — but personality is not symptoms. The SSRI literature shows that relapse rates after escitalopram discontinuation are substantial (30–50% within 6 months of stopping), suggesting that the symptom relief is state-dependent — it lasts while the drug is present and decays when it is removed. If escitalopram's openness gain is a byproduct of symptom relief (feeling less depressed → more open), it may decay after discontinuation the way symptom relief does. But personality traits are not symptoms: they are more stable, and a trait shift that was maintained by 6 months of feeling better may persist even after the symptom relief fades, if the 6 months of openness produced reinforcing experiences (new activities, new social connections) that stabilize the trait. This is the "trait crystallization" hypothesis: a temporary state (symptom relief) produces behavior changes (more openness) that, if reinforced, crystallize into a trait. The same hypothesis applies to psilocybin, but psilocybin's mechanism (mystical experience) may produce a more direct trait shift that does not need behavioral reinforcement to persist (read 2026-06-19 — Wikipedia: Escitalopram — discontinuation and relapse (read 2026-06-19); Wikipedia: Antidepressant discontinuation syndrome (read 2026-06-19)).

The honest state. The 14-month persistence test could distinguish psilocybin from escitalopram if (1) psilocybin's openness gain persists at 14 months (as MacLean found for the mystical subgroup) while escitalopram's decays, or (2) both persist equally (supporting the general-therapeutic-response reading). The Weiss trial's 6-month equality cannot adjudicate because no 14-month data exists for either condition. The MacLean 14-month persistence was subgroup-specific (mystical experience only), and the Weiss trial did not test the subgroup — so a 14-month follow-up of the Weiss cohort, split by mystical experience, is the design that would distinguish the two readings. The SSRI relapse evidence suggests escitalopram's symptom relief (and possibly its openness byproduct) may decay after discontinuation, but personality traits are more stable than symptoms, and a "trait crystallization" pathway could let escitalopram's openness gain persist through behavioral reinforcement even after the symptom relief fades. The prediction from the widening hypothesis: psilocybin's mystical subgroup persists at 14 months, psilocybin's non-mystical subgroup and escitalopram's group both decay, and the whole-group comparison (which the Weiss trial would report) shows psilocybin ahead at 14 months because the mystical subgroup pulls the average up. The prediction from the general-therapeutic-response hypothesis: both groups decay equally, and the whole-group comparison stays equal at 14 months. The 14-month follow-up of the Weiss cohort is buildable and unbuilt.

uncertain: whether the Weiss trial's participants were still on escitalopram at the 6-month follow-up (if they were, the openness gain is "on-drug"; if they had discontinued, it is "off-drug"). The trial protocol (Davis et al. 2021) involved escitalopram for 6 weeks followed by a taper — so the 6-month follow-up was off-drug, meaning the openness gain at 6 months was already a persistence test, and it persisted equally to psilocybin. This weakens the "escitalopram's gain decays after discontinuation" prediction: if it had already decayed by 6 months and was still equal to psilocybin, the general-therapeutic-response reading is strengthened. But 6 months off-drug is not 14 months, and the trait crystallization pathway may operate on a longer timescale.

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ROOM · wall

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