Inclusion Criteria
For EPP:
* Diagnosis as assessed using DSM-5 of one of the following: schizophrenia, schizophreniform psychosis, psychosis not otherwise specified (NOS), brief psychosis, schizoaffective syndrome, delusional disorder
* Onset of psychotic symptoms together with functional decline no more than 3 years prior to inclusion visit
For CHR-P:
Clinical high risk for psychosis as determined using Structured Interview for Psychosis-risk Syndromes (SIPS).
Exclusion Criteria
For EPP and CHR-P:
* Other dominant psychiatric illness that is deemed to be related to current psychotic symptoms (including bipolar disorder, major depressive disorder, autism)
* Long-term daily treatment (\<2 weeks) with benzodiazepines, such that there is an inability to refrain from treatment during testing procedures.
For HC:
* A history of diagnosis of a major psychiatric disorder, including substance use disorders.
* A family history of psychotic disorders or bipolar disorder in first degree relatives.
For all participants:
* Evidence based on medical history, clinical signs, MRI or laboratory tests of clinically significant somatic disorder, or previous disorder with brain engagement (e.g. tumour, neuroinflammatory disease, epilepsy) or significant brain trauma.
* Exposure to an effective radiation dose of 25 mSv during the past year.
* Pregnancy, lactating or breastfeeding (women).
* Lack of proficiency in Swedish language, or documented intellectual disability that prohibits ability to give informed consent.
* Meets diagnostic criteria of substance use disorder (excluding nicotine dependence) as assessed using DSM-5 or as determined using repeated positive urine screens during the course of the study.
* Metallic object in the eye, or ferro/electromagnetic implants. History of claustrophobic anxiety during MRI.
* Symptoms of severe bacterial, fungal, or viral infection (including upper respiratory tract infection), with systemic effects as detected by e.g. fever, within 7 days prior to inclusion.
* Treatment with any antihemostatic medication within 2 weeks of lumbar puncture and arterial line placement of either the baseline or 1 year follow-up.
* Blood donation (1 unit or more) within 90 days prior to Screening, plasma donation from 1 week prior to Screening, and platelet donation from 6 weeks prior to inclusion.
* Other unspecified reasons that, in the opinion of the Investigator or the Sponsor, make the participant unsuitable for enrollment. This may include very high symptom severity or signs of aggressiveness and hostility.
