Subtypes (disorders)

Subtypes of disorders are designated where their are variations in presentation which require a diagnostic subclassification.

So for example in Schizophrenia a number of subtypes have been included in the DSM-IV-TR which contains five sub-classifications of schizophrenia, although the developers of DSM-5 are recommending they be dropped from the new classification:
 * Paranoid type: Delusions or auditory hallucinations are present, but thought disorder, disorganized behavior, or affective flattening are not. Delusions are persecutory and/or grandiose, but in addition to these, other themes such as jealousy, religiosity, or somatization may also be present. (DSM code 295.3/ICD code F20.0)
 * Disorganized type: Named hebephrenic schizophrenia in the ICD. Where thought disorder and flat affect are present together. (DSM code 295.1/ICD code F20.1)
 * Catatonic type: The subject may be almost immobile or exhibit agitated, purposeless movement. Symptoms can include catatonic stupor and waxy flexibility. (DSM code 295.2/ICD code F20.2)
 * Undifferentiated type: Psychotic symptoms are present but the criteria for paranoid, disorganized, or catatonic types have not been met. (DSM code 295.9/ICD code F20.3)
 * Residual type: Where positive symptoms are present at a low intensity only. (DSM code 295.6/ICD code F20.5)

The ICD-10 defines two additional subtypes:
 * Post-schizophrenic depression: A depressive episode arising in the aftermath of a schizophrenic illness where some low-level schizophrenic symptoms may still be present. (ICD code F20.4)
 * Simple schizophrenia: Insidious and progressive development of prominent negative symptoms with no history of psychotic episodes. (ICD code F20.6)

As we can see from this there is some doubts about the clarity of any distinctions made.