At least two of the following symptoms must be present for a period of 1 month or more, and one must be a positive symptom: persistent delusions, persistent hallucinations, disorganised thinking, experiences of influence, passivity or control which can come along with either another positive symptom or negative symptoms (such as affective flattening, alogia/paucity of speech, avolition and anhedonia or grossly disorganised speech that impeded goal-directed activity or psychomotor disturbances)