5ml b.i.d for 6 weeks; For participants with a weight lower than 50 kg, the dose is to be adjusted to 20 mg/kg/day divided over 2 intakes of 10 mg/kg/day, for a period of 12 weeks

Symptomatic remission after 12 weeks as measured using the Positive and Negative Syndrome Scale (PANSS), defined using Andreasen (2005) remission criteria.

Remission is based on the following PANSS: Positive symptoms: P1, P2, P3. Negative symptoms: N1, N4, N6. General psychopathology: G5, G9.Minimum score: 1 (absent); Maximum score: 7 (extreme). Lower scores are better outcome; Higher scores are worse outcome.

Andreasen, N. C., Carpenter, W. T., Jr, Kane, J. M., Lasser, R. A., Marder, S. R., & Weinberger, D. R. (2005). Remission in schizophrenia: proposed criteria and rationale for consensus. The American journal of psychiatry, 162(3), 441-449. https://doi.org/10.1176/appi.ajp.162.3.441

Change in overall clinical impression, assessed through Clinical Global Impression of Improvement and Severity (CGI-I/S) scales from baseline to 12 weeks. Clinical Global Impression of Severity (CGI-S) is rated from 1 (normal, not at all ill) to 7 (among the most extremely ill), with lower scores indicating lower illness severity. Clinical Global Impression of Improvement (CGI-I) is rated from 1 (very much improved) to 7 (very much worse), with lower scores indicating greater clinical improvement.

Change in functioning, assessed through Social and Occupational Function Scale (SOFAS) from baseline to 12 weeks.

Score range 1-100, the higher score means the better function

Change in cognitive functioning as assessed through the PsyCog battery from baseline to 12 weeks.

PsyCog comprises the tests that were chosen from the larger CANTAB battery to assess the key cognitive deficits associated with psychosis, including:

o Paired Associates Learning (PAL): key measures including PAL total errors adjusted (score range 0-70; lower is better) and PAL first attempt memory score (score range 0-20; higher is better).

Change in cognitive functioning as assessed through the PsyCog battery from baseline to 12 weeks.

PsyCog comprises the tests that were chosen from the larger CANTAB battery to assess the key cognitive deficits associated with psychosis, including:

o Rapid Visual Information Processing (RVP): key measures including RVP A' (score range 0-1; higher is better) and RVP median response latency(ms) (score range 100-1900; lower is better).

Change in cognitive functioning as assessed through the PsyCog battery from baseline to 12 weeks.

PsyCog comprises the tests that were chosen from the larger CANTAB battery to assess the key cognitive deficits associated with psychosis, including: Emotion Recognition Task (ERT): key measures including ERT overall median reaction time (ms) (score range 100-00; lower is better) and ERT total hits (score range 0-48; higher is better).

Change in quality of life, assessed using the EuroQol 5-Dimension, 3-Level Questionnaire (EQ-5D-3L) from baseline to 12 weeks. It includes five dimensions-MOBILITY, SELF-CARE, USUAL ACTIVITIES, PAIN /DISCOMFORT and ANXIETY / DEPRESSION. Each dimension has three levels: no problems, some problems, extreme problems (labelled1-3). The respondent is asked to indicate his / her health state by checking the box against the most appropriate statement in each of the five dimensions.

The EQ VAS records the respondent's self-rated health on a vertical VAS where the endpoints are labelled 'The best health you can imagine' and 'The worst health you can imagine'. This information can be used as a quantitative measure of health outcome as judged by the individual respondents. Score range: Minimum: 0 (worst imaginable health); Maximum: 100 (best imaginable health). Higher scores indicate better health; Lower scores indicate worse health.

Change in quality of life, assessed using the World Health Organization Quality-of-Life Scale (WHOQOL-BREF) from baseline to 12 weeks.

The WHOQOL-BREF is a 26-item instrument consisting of four domains: physical health (7 items), psychological health (6 items), social relationships (3 items), and environmental health (8 items); it also contains QOL and general health items. Each individual item of the WHOQOL-BREF is scored from 1 to 5 on a response scale, which is stipulated as a five-point ordinal scale.

Acceptability of CBD treatment, measured through Clinician rating scale (CRS) to assess adherence to trial medication (Kemp et al., 1998) and all-cause discontinuation over 12 weeks. Clinical rating scale score range: Minimum: 1; Maximum: 7. Higher scores are better outcome; Indicate greater adherence to trial medication. Lower scores are worse outcome; Indicate poor or absent adherence.

Incidence of adverse events, measured through Glasgow Antipsychotic Side-effect Scale (GASS) over 12 weeks. Spontaneous adverse event reporting is until 30 days after the study intervention has been discontinued.

Measure the severity of anxiety symptoms via Hamilton Anxiety Scale (HAM-A) from baseline to 12 weeks.

Each item is scored on a scale of 0 (not present) to 4 (severe), with a total score range of 0-56, where <17 indicates mild severity, 18-24 mild to moderate severity and 25-30 moderate to severe.

Measure the severity of anxiety symptoms via the Overall Anxiety Severity and Impairment Scale (OASIS) from baseline to 12 weeks.

It consists of five items that measure the frequency and severity of anxiety, as well as level of avoidance, work/school/home interference, and social interference associated with anxiety. Respondents select among five different response options for each item, which are coded 0-4 and summed to obtain a total score. Score range is 0-20. The lower score is better in symptoms.

Measure the depression in schizophrenia without overlap with negative symptoms and extrapyramidal symptoms by using the Calgary Depression Scale for schizophrenia (CDSS) from baseline to 12 weeks.

it includes 9 items in the scale. All ratings of the items are defined according to operational criteria from 0-3. The CDSS depression score is obtained by adding each of the item scores. Score range is 0-27, which is the lower score is better.

Measure the neuroimaging (Magnetic resonance imaging (MRI)) from baseline to 12 weeks if participant consents to it.

The Magnetic resonance imaging (MRI) scan includes:

T1 - brain structure T2 FLAIR - brain structure / clinical reporting Neuromelanin sensitive MRI - neuromelanin content of substantial nigra (proxy of dopamine activity) Magnetic Resonance Spectroscopy of the anterior cingulate cortex - metabolites e.g. glutamate Resting state fMRI - bold activation during "rest" or free mind wandering

Measure the microbiome samples from baseline to 12 weeks if participant consents to it.

The gut-microbiome (the microorganisms e.g. bacteria, normally found in participant's gut) is likely to be at play in determining whether participant respond or experience side effects from CBD.

Two tubes of stool samples to be collected at two time points(baseline and week 12) if participant consent to it.

Measure the blood samples for central lab assessment including (Epi)genetics, proteomics, inflammation, metabolomics, Redox markers from baseline to 12 weeks if participant consents to it.