Psychosis
"Psychosis" is a generic term that refers to distortions and impairments of thought, feeling, and behaviour leading to a loss of contact with consensual reality. It is signified by delusions, hallucinations, thought disorder, grossly disorganised or abnormal motor behaviour, and negative symptoms (APA, 2013). At the categorical level, schizophrenia-spectrum disorders include schizophrenia, schizophreniform disorder, schizoaffective disorder, delusional disorder, brief psychotic disorder, substance/medication-induced psychotic disorder, schizotypal (personality) disorder, psychotic disorder due to another medical condition, catatonia, and other specified and unspecified schizophrenia spectrum and other psychotic disorders (APA, 2013; WHO, 2018). Importantly, psychotic symptoms can be found in a range of other disorders, although not as a defining feature, most notably in mood disorders (major depression and bipolar disorder), substance-related and addictive disorders, posttraumatic stress disorder, borderline personality disorder, and neurocognitive disorders (e.g., Alzheimer’s disease). At the symptom level, psychotic symptoms and psychotic-like symptoms are also found in the general population, and people with these experiences may or may not require care.
Schizophrenia has received various narrower and broader definitions over time. It is the psychotic disorder that attracts most attention and one reason may be that it is the most common; for example, the lifetime prevalence of schizophrenia is about 0.9%, compared to 0.3% for schizoaffective disorder (Perala et al., 2007). Most patients receive antipsychotic medication; yet, they do not improve functional outcome. Approximately 50-75% of the patients discontinue medication, and the rate of relapse is high even in patients who are prescribed second-generation antipsychotics (Moritz et al., 2014). Psychological treatment is beneficial in improving symptoms, even in the absence of pharmacological treatment where 40% of the patients significantly improve their symptoms (Morrison et al., 2014). Among the most effective psychological interventions is Metacognitive Training (MCT), based on Cognitive Behaviour Therapy (CBT) one of the guideline treatments for psychosis (NICE, 2014).