Inclusion
Capacity to provide informed consent.
Stated willingness to comply with all study procedures and availability for the duration of the study.
Male or female, age \>= 65 years old.
Cognitive Status:
Early-stage AD population: Meets the 2024 Alzheimer s Association Workgroup revised criteria for diagnosis and staging of AD (symptomatic cognitive impairment consistent with amnestic MCI or mild AD dementia) with a CDR score of 0.5-1 (including 0.5 for the memory box) and a Montreal Cognitive Assessment (MoCA) score of 20-25.
Cognitively normal population: No cognitive impairment based on history and examination, with a CDR score of 0 and MoCA score \>= 26.
For participants with early-stage AD, evidence of underlying AD pathology by the only FDA-approved blood-based test, Lumipulse G p217-Tau/Abeta42 ratio \>= 0.00738. Alternatively, participants who previously underwent amyloid PET or CSF testing for diagnosis of AD (to qualify for treatment with anti-amyloid monoclonal antibodies or for any other reason) may provide report of the amyloid PET scan or results of CSF analysis compatible with underlying AD pathophysiology; Lumipulse G p217-Tau/Abeta42 will still be measured to maintain consistency in study assessments, but values \< 0.00738 will not disqualify them.
Absence of serious neuropsychiatric symptoms, defined as a score of 0 on Delusions and Hallucinations items and a score \<= 2 on Anxiety, Aggression, Irritability, and Disinhibition items of the Neuropsychiatric Inventory Questionnaire (NPI-Q).
Acetylcholinesterase inhibitors and/or memantine are permitted (alone or in combination) provided the dose(s) have been stable for (Bullet) 6 weeks prior to screening and remain stable through the psilocybin dosing period and primary outcome assessments, unless a change is medically necessary.
Concurrent pharmacotherapy with a single selective serotonin reuptake inhibitor (SSRI), serotonin and norepinephrine reuptake inhibitor (SNRI), tricyclic anti-depressant (TCA) or monoamine oxidase inhibitor (MAOI) is allowed if the participant is willing and able to taper off this medication after Visit 1 (Screening) and stay off it for a washout period of at least 7 +/- 2 days prior to Visit 2 (Baseline) and at least 14 +/- 2 days prior to Visit 3 (for the Psilocybin + Cognitive Training group) or Visit 4 (for the Cognitive Training alone group). Bupropion (\<= 300 mg/day) is permitted without taper or washout if the dose has been stable for \>= 6 weeks before screening.
Absence of active suicidal ideation with plan/intent and no suicidal behavior within the past 6 months, as defined by Columbia-Suicide Severity Rating Scale (C-SSRS) of 0 or 1. Participants with passive ideation (severity 1) may be included only if risk is judged low, a safety plan is documented, and there is no suicidal behavior in the prior 6 months.
For the early-stage AD population, participation of a study partner who is willing and able to serve as a medical history informant, accompany participants during visits, and provide psychological support following psilocybin sessions. For the cognitively normal population, participation of a study partner will be encouraged, but not mandated as eligibility criterion.
Ability to take oral medication.
Pregnancy prevention:
Participants of childbearing potential must have a negative urine pregnancy test at screening and prior to psilocybin on Visits 3 and 7, and agree to use highly effective birth control beginning at least 14 days before any psilocybin dosing day and continuing through 30 days after the last psilocybin dose.
Male participants with partners of childbearing potential must agree to use condoms and to ensure their partner uses a highly effective contraceptive method during the same window. Sperm donation is not permitted during the study and for 30 days after the last psilocybin dose.
Exclusion
Medical history
Neurological disorders (besides AD): Brain disorders, either previously diagnosed or revealed through screening exams or baseline neuroimaging, including:
Stroke (except single asymptomatic old lacune)
Transient Ischemic Attack (TIA) within the past year, unless work-up shows no ongoing risk
Extensive microvascular pathology or microbleeds
Multiple sclerosis or demyelinating disorders
Parkinson s disease or movement disorders (e.g., Multiple Systems Atrophy, Progressive Supranuclear Palsy)
Brain tumors
History of meningitis or encephalitis
History of moderate/severe traumatic brain injury (Glasgow Coma Scale \<= 12)
Other dementias
Epilepsy
Psychiatric disorders:
Current or past moderate-to-severe mood disorders
History of psychotic disorders unless remote, short-lived, and directly attributable to medication misuse or overdose
Active suicidal ideation (C-SSRS severity 2-5) within the past 1 month or any suicidal behavior within the past 6 months; or current elevated acute risk in the opinion of the medically responsible investigator
Severe PTSD, defined as a Primary Care PTSD Screen for DSM-5 (PC-PTSD-5) score \>= 4 in men or \>= 3 in women
Anxiety or personality disorders, if moderate to severe, as determined by the medically responsible investigator.
Cardiovascular conditions:
Any history of coronary artery disease
Clinically significant electrocardiographic (EKG) abnormalities (e.g., atrial fibrillation/flutter, QTc \> 450 ms, evidence of myocardial infarct history, high-grade conduction disease, or other rhythm/conduction abnormalities). For EKG abnormalities other than QTc \> 450 ms, clinical significance may be corroborated by transthoracic echocardiogram (TTE).
Uncontrolled hypertension (systolic blood pressure (SBP) \> 150 mmHg or diastolic blood pressure (DBP) \> 95 mmHg) confirmed after \>=5 minutes seated rest using 3 readings averaged.
Resting heart rate (HR) 55 bpm or \> 100 bpm or clinically significant arrythmia: HR will be assessed concurrently with the blood pressure protocol above.
Clinically significant cardiomyopathy (e.g., hypertrophic, dilated, restrictive) or heart failure
Moderate to severe valvular heart disease (valvulopathy) or pulmonary hypertension
Metabolic disorders:
Insulin-dependent diabetes mellitus
Renal impairment (eGFR \< 60 ml/min/1.73 m2)
Liver function tests \> 2x upper limit of normal
Infectious \& Hematologic Conditions:
Positive HIV, HBV, or HCV status
Anemia (HGB \< 12 g/dL in men, \< 11 g/dl in women)
Poor venous access
Medications Exclusions
Absolute
Typical \& atypical antipsychotics
Multiple antidepressants medications (i.e., combinations of SSRIs, SNRIs, MAOIs, TCAs and bupropion). Bupropion (\<= 300 mg/day) is permitted without taper or washout if the dose has been stable for \>= 6 weeks before screening.
Relative
Benzodiazepines and non-benzodiazepine sedative-hypnotics (e.g., zolpidem, eszopiclone):
Regular use: participants must be willing and able to taper off and remain off for at least 14 +/- 2 days prior to Visit 3 (for the psilocybin + cognitive training group) or Visit 4 (for the cognitive training alone group), due to potential confounding effects on EEG recordings and sleep architecture and potential attenuation of the acute psilocybin experience. Because benzodiazepine withdrawal can cause clinically significant symptoms (and, rarely, seizures), tapering must be gradual. Discontinuation schedule will be directed by the medically responsible investigator in coordination with the prescribing clinician per participant wishes; participants with evidence of physiologic dependence or for whom safe tapering is not feasible within the study timeline will not be eligible for further study participation.
Intermittent PRN use: participants may be eligible if they can hold these medications for at least 72 hours prior to each psilocybin dosing session (for the psilocybin + cognitive training group) and avoid use during the overnight EEG recording window.
Sleep-inducing medications (e.g., trazodone, sedative-hypnotics) should not be taken for at least 14 +/- 2 days before Visit 3 (for the psilocybin + cognitive training group) or Visit 4 (for the cognitive training alone group) (due to potential confounding effects on EEG recordings and sleep architecture)
Melatonin (and similar over-the-counter sleep aids) should not be taken for at least 72 hours prior to Visit 3 (for the psilocybin + cognitive training group) or Visit 4 (for the cognitive training alone group), due to potential confounding effects on EEG recordings
Mood stabilizers (e.g., lithium), long-acting opioids (unless they are willing and able to taper off after Visit 1 (Screening) and have stayed off for a washout period of at least 7 +/- 2 days prior to Visit 2 (Baseline) and at least 14 +/- 2 days prior to Visit 3 (for the psilocybin + cognitive training group)). Participants taking lithium will be eligible only if (i) lithium is being used for a condition where supervised discontinuation is clinically appropriate (e.g., augmentation for unipolar depression or another non-bipolar indication), (ii) there is no history of bipolar disorder/mania, and (iii) the prescribing clinician confirms that a gradual taper and washout can be completed safely before baseline/dosing. During any lithium taper/washout, participants will be monitored for symptom recurrence and safety concerns; if relapse risk is unacceptable, participants will be excluded from further study participation.
Sildenafil, tadalafil, or similar medications should not be taken within 72 hours of psilocybin administration (for the psilocybin + cognitive training group)
UGT1A10 and 1A9 inhibitors (e.g., diclofenac, probenecid) should not be taken within 72 hours of psilocybin administration (for the psilocybin + cognitive training group)
Alkaline phosphatase inhibitors (e.g., cinacalcet) should not be taken within 72 hours of psilocybin administration (for the psilocybin + cognitive training group)
Serotonin agonists (e.g., migraine medications like triptans) should not be taken within 72 hours of psilocybin administration (for the psilocybin + cognitive training group)
Serotonergic supplements, such as St. John s Wort, should not be taken within 72 hours of psilocybin administration (for the psilocybin + cognitive training group)
Substance Use History
Psychedelic substance use within the past year by self-report. This criterion aims to minimize potential confounding effects of recent psilocybin exposure on study outcomes.
Positive urine drug screen for substances of use, including cannabis (THC), cocaine, amphetamines, methamphetamines, MDMA (ecstasy), opioids, phencyclidine (PCP), barbiturates, and benzodiazepines.
Participants testing positive for cannabis (THC) may be eligible for re-screening after a 4-8-week washout period.
Anti-Amyloid Monoclonal Antibodies
Participants actively receiving FDA-approved IV or SC anti-amyloid monoclonal antibodies (including lecanemab, donanemab, or aducanumab) will be excluded.
Participants who previously received any anti-am...