Participants will receive either a single high-dose of psilocybin (25mg absolute dose) or methylphenidate (40mg absolute dose). Participants will be asked to complete assessments of pain, depressive symptoms, and more general questionnaires regarding the participants experiences during the experimental sessions and the associated enduring effects. conditions: Chronic Low-back Pain conditions: Depression studyType: INTERVENTIONAL phases: PHASE1 allocation: RANDOMIZED interventionModel: PARALLEL interventionModelDescription: Randomized, double-blind, active control study comparing the effects of psilocybin (25mg fixed dose) and methylphenidate (40mg fixed dose) primaryPurpose: TREATMENT masking: TRIPLE maskingDescription: This is a double-blind trial, and efforts will be made to mask the study drug (psilocybin) and the active control (methylphenidate) from participants, guides, and study staff. Participants will be debriefed about their randomly assigned drug condition after the completion of the final follow-up assessment, or after discontinuation/withdrawal, whichever comes first. whoMasked: PARTICIPANT whoMasked: INVESTIGATOR whoMasked: OUTCOMES_ASSESSOR count: 40 type: ESTIMATED name: Psilocybin name: Methylphenidate measure: Changes in positive affect as assessed by discrete positive affect items and averaged over 7-day periods of Ecological Momentary Assessment (EMA) measure: Changes in negative affect as assessed by discrete negative affect items and averaged over 7-day periods of Ecological Momentary Assessment (EMA) measure: Changes in Pain Catastrophizing as assessed by the Pain Catastrophizing Scale and averaged over 7-day periods of Ecological Momentary Assessment (EMA) measure: Changes in Positive Affective Pain Inhibition (Quantitative Sensory Testing) measure: Changes in positive affect as assessed by discrete positive affect items and averaged over 7-day periods of Ecological Momentary Assessment (EMA) measure: Changes in negative affect as assessed by discrete negative affect items and averaged over 7-day periods of Ecological Momentary Assessment (EMA) measure: Changes in Pain Catastrophizing as assessed by the Pain Catastrophizing Scale and averaged over 7-day periods of Ecological Momentary Assessment (EMA) measure: Changes in Positive Affective Pain Inhibition (Quantitative Sensory Testing) measure: Pain as assessed by discrete pain items assessed via EMA measure: Dynamic association between affect and pain using micro-longitudinal EMA data of affective variables (positive, negative affect outcomes) and pain outcomes measure: Changes in mood as measured by a selection of discrete items derived from the Positive and Negative Affect Schedule- Expanded Form (PANAS-X). measure: Changes in self-reported Pain Impact as measured by Pain intensity (P), interference with Enjoyment of life (E), and interference with General activity (G) Scale (PEG) measure: Changes in Pressure Pain Threshold (Quantitative Sensory Testing) measure: Changes in Conditioned Pain Modulation (Quantitative Sensory Testing) measure: Chronic Pain Exacerbation as measured by the Graded Chronic Pain Scale- Revised (GCPS-R) measure: Changes in neuropathic pain features as assessed by the painDETECT questionnaire (PDQ) measure: Changes in CLBP-related disability as measured by the Oswestry Disability Index (ODI) measure: Change in Emotion Regulation as assessed by the Difficulties in Emotion Regulation Scale (DERS) measure: Pain intensity and related dimensions of health (i.e., sleep) as measured by the Patient-Reported Outcomes Measurement Information System (PROMIS-29 v2.0). measure: Psychological Inflexibility in Pain as measured by the Psychological Inflexibility in Pain Scale (PIPS) measure: Personal values and the degree of success in following those values as measured by the Chronic Pain Values Inventory (CPVI). measure: Dispositional tendencies to feel positive emotions towards others in daily life as measured by the Dispositional Positive Emotion Scale (DPES) measure: Mindfulness as measured by the Five Facet Mindfulness Questionnaire (FFMQ-15) measure: Subjective experiences: Awe Experience Scale (AWE-S) measure: Subjective experiences: Mystical Experience Questionnaire (MEQ30) measure: Subjective experiences: Challenging Experience Questionnaire (CEQ) measure: Subjective experiences: Altered States of Consciousness Questionnaire (5D-ASC) measure: Subjective experiences: Psychological Insight Questionnaire (PIQ) measure: Changes in basic beliefs about the world as measured by the Primals Inventory (PI-6) sex: ALL minimumAge: 21 Years maximumAge: 65 Years stdAges: ADULT stdAges: OLDER_ADULT facility: Johns Hopkins University School of Medicine status: RECRUITING city: Baltimore state: Maryland zip: 21224 country: United States name: David Yaden, PhD role: CONTACT phone: 410-550-5250 phoneExt: 0-5250 email: dyaden1@jhmi.edu name: David Yaden, PhD role: PRINCIPAL_INVESTIGATOR name: Patrick Finan, PhD role: SUB_INVESTIGATOR lat: 39.29038 lon: -76.61219 hasResults: False