ICD-11 Criteria for Disorders due to use of Unknown or Unspecified Psychoactive Substances (6C4G) Disorders due to use of unknown or unspecified psychoactive substances are characterised by the pattern and consequences of psychoactive substance use when the specific substance is unknown or unspecified. These categories may be used in clinical situations in which it is clear that the disturbance is due to substance use but the specific class of substance is unknown. Once the relevant substance is identified, the disturbance should be recoded under the appropriate substance class. 6C4G.0      Episode of harmful use of unknown or unspecified psychoactive substances An episode of use of an unknown or unspecified psychoactive substance that has caused damage to a person’s physical or mental health or has resulted in behaviour leading to harm to the health of others. Harm to health of the individual occurs due to one or more of the following: (1) behaviour related to intoxication or wi