In general, psychosis refers to the presence of hallucinations (false perceptions), delusions (false, fixed ideas, which carry overwhelming significance for the patient), loss of insight, ipseity disturbance and thought disorder. For over 100 years the psychoses have been divided into organic and functional categories.
Organic denotes an identifiable systemic or central pathology. Organic psychoses can be secondary to endocrine disorders (thyroid disease); metabolic disease (acute intermittent porphyria); autoimmune disorders (paraneoplastic limbic encephalitis, NMDA receptor encephalitis [Link]); infection (herpes simplex encephalitis); seizures (temporal lobe epilepsy); space-occupying lesions; stroke; head-injury; demyelinating diseases (metachromatic leukodystrophy); neurodegenerative disease (Lewy-body dementia); basal ganglia disorders (Wilson’s disease); nutritional deficiencies (B12 deficiency); medications (acyclovir); environmental toxins (thallium); and psychoactive drugs (LSD, ketamine, cannabis and stimulants [Link]).
The identification of an organic psychosis depends upon a thorough history, physical examination and the prudent use of laboratory investigations. Identification of an organic cause of the psychosis can dramatically change the subsequent management and prognosis.
Functional psychoses are diagnoses of exclusion (i.e. exclusion of identifiable organic pathology). There are as yet no diagnostic tests. Diagnosis is made of clinical grounds (symptoms/signs) according to the criteria in the Diagnostic & Statistical Manual of the American Psychiatric Association (APA, DSM-IV-TR) or the International Classification of Diseases of the World Health Organisation (WHO, ICD-10) [Link]. The two classification systems are broadly similar. They subdivide the functional psychoses into schizophrenia (paranoid type, disorganised/hebephrenic type, catatonic, undifferentiated, residual [and simple in ICD-10]); persistent delusional disorders, schizophreniform disorder (DSM-IV-TR), brief psychotic disorders and schizoaffective disorder. Psychotic symptoms can also occur in bipolar disorder and major depressive disorder.
For a DSM-IV-TR diagnosis of schizophrenia, the following criteria must be met: 1.The presence of characteristic symptoms [at least two, (or one if delusions are bizarre/or if auditory hallucinations form a running commentary or discuss the patient.)] for most of the time for one month (or less if treated), which can be delusions, hallucinations, disorganised speech, grossly disorganised behaviour or negative symptoms (blunted affect, alogia or avolition). 2. Social or occupational dysfunction. 3. Continuous signs of disturbance for six months (including one month of psychotic symptoms). Caveats are that the symptoms cannot be secondary to a mood disorder, a pervasive developmental disorder, or as a result of an identifiable organic illness – (the last of which would takes us back to the top of the page here).