Inclusion Criteria:
For FEP:
* Diagnosis as assessed using DSM-IV of one of the following: schizophrenia, schizophreniform psychosis, psychosis not otherwise specified (NOS), brief psychosis, schizoaffective syndrome, delusional disorder
* First exposure to anti-psychotic medication less than 4 weeks prior to inclusion
Exclusion Criteria:
For FEP:
\- Other dominant psychiatric illness deemed to be related to current psychotic symptoms
For HC:
* A history of diagnosis of a major psychiatric disorder, including substance use disorders.
* Family history of psychotic disorders in first degree relatives.
For all:
* 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).
* Meets diagnostic criteria of substance use disorder (excluding nicotine dependence) as assessed using DSM-IV 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.
