Antipsychotic Dosing"Extended" (Alternate Day) Antipsychotic Dosing

Inclusion Criteria:

(i) A primary diagnosis of a Schizophrenia Spectrum or Other Psychotic Disorder as defined by the DSM-5 diagnosis and confirmed by the MINI (Version 7.0.2)

(ii) age 18 or older

(iii) female participants of childbearing potential must be using a reliable method of contraception and have a negative pregnancy test at the time of enrolment and must, in the investigator's opinion, practice a clinically accepted, reliable method of contraception during this study. Male participants must not father a baby during their time in the study

(iv) ability to communicate in English

(v) capacity to provide written, informed consent, as assessed using the MacCAT-CR at time of consent

(vi) stabilized as outpatients with a single oral AP (risperidone or olanzapine or paliperidone\*) at the same dose for ≥3 months i. On a prescribed risperidone dose of between 1-6mg, or a prescribed olanzapine dose of between 5-20mg, or a prescribed paliperidone 3-12mg

(vii) evidence of adherence with current AP treatment

Exclusion Criteria:

(i) exposure to a depot AP within 1 year (i.e., no depot AP injection within the last year)

(ii) Current diagnosis of substance use disorder according to DSM-5 criteria (verified through the MINI for Psychotic Disorders (Version 7.0.2) and a positive drug screen for street and /or prescription drugs not prescribed to the participant by treating physicians

(iii) ECT within the last 3 months

(iv) pregnancy or lactation

(v) neurological condition (dementia including Alzheimer's disease, multiple sclerosis, epilepsy, stroke, or traumatic brain injury)

(vi) allergy to the study drugs and their excipients

(vii) allergy (e.g., galactosaemia) or severe intolerance to lactose

(viii) negative urine drug screen result for Olanzapine or Risperidone or Paliperidone (if applicable)