A pattern of psychoactive substance use that is causing damage to health. The damage may be physical (e.g. hepatitis following injection of drugs) or mental (e.g. depressive episodes secondary to heavy alcohol intake). Harmful use commonly, but not invariably, has adverse social consequences; social consequences in themselves, however, are not sufficient to justify a diagnosis of harmful use. The term was introduced in ICD-I0 and supplanted "non-dependent use" as a diagnostic term. 

• Hazardous use - A pattern of substance use that increases the risk of harmful consequences for the user. Some would limit the consequences to physical and mental health (as in harmful use); some would also include social consequences. In contrast to harmful use, hazardous use refers to patters of use that are of public health significance despite the absence of any current disorder in the individual user. The term is used currently by WHO but is not a diagnostic term in ICD-I1 (WHO Lexicon of alcohol and drug terms).

WHO ICD-11:

6C44.1 Harmful pattern of use of sedatives, hypnotics or anxiolytics - A pattern of sedative, hypnotic, or anxiolytic use that has caused clinically significant harm to a person’s physical or mental health or in which behaviour induced by sedatives, hypnotics or anxiolytics has caused clinically significant harm to the health of other people. The pattern of sedative, hypnotic, or anxiolytic use is evident over a period of at least 12 months if use is episodic and at least one month if use is continuous (i.e., daily or almost daily). Harm may be caused by the intoxicating effects of sedatives, hypnotics or anxiolytics, the direct or secondary toxic effects on body organs and systems, or a harmful route of administration. 

6C40.0 Episode of harmful use of alcohol - An episode of use of alcohol 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; (2) direct or secondary toxic effects on body organs and systems; or (3) a harmful route of administration. Harm to health of others includes any form of physical harm, including trauma, or mental disorder that is directly attributable to behaviour due to alcohol intoxication on the part of the person to whom the diagnosis of single episode of harmful use applies. This diagnosis should not be made if the harm is attributed to a known pattern of alcohol use. 

6C40.1 Harmful pattern of use of alcohol - A pattern of alcohol use 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. The pattern of alcohol use is evident over a period of at least 12 months if substance use is episodic or at least one month if use is continuous. Harm to health of the individual occurs due to one or more of the following: (1) behaviour related to intoxication; (2) direct or secondary toxic effects on body organs and systems; or (3) a harmful route of administration. Harm to health of others includes any form of physical harm, including trauma, or mental disorder that is directly attributable to behaviour related to alcohol intoxication on the part of the person to whom the diagnosis of Harmful pattern of use of alcohol applies. 

6C41.0 Episode of harmful use of cannabis – An episode of use of cannabis 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; (2) direct or secondary toxic effects on body organs and systems; or (3) a harmful route of administration. Harm to health of others includes any form of physical harm, including trauma, or mental disorder that is directly attributable to behaviour due to cannabis intoxication on the part of the person to whom the diagnosis of single episode of harmful use applies. This diagnosis should not be made if the harm is attributed to a known pattern of cannabis use. 

6C41.1 Harmful pattern of use of cannabis - A pattern of cannabis use 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. The pattern of cannabis use is evident over a period of at least 12 months if substance use is episodic or at least one month if use is continuous (i.e., daily or almost daily). Harm to health of the individual occurs due to one or more of the following: (1) behaviour related to intoxication; (2) direct or secondary toxic effects on body organs and systems; or (3) a harmful route of administration. Harm to health of others includes any form of physical harm, including trauma, or mental disorder that is directly attributable to behaviour related to cannabis intoxication on the part of the person to whom the diagnosis of Harmful pattern of use of cannabis applies. 

6C43.0 Episode of harmful use of opioids - An episode of opioid use 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; (2) direct or secondary toxic effects on body organs and systems; or (3) a harmful route of administration. Harm to health of others includes any form of physical harm, including trauma, or mental disorder that is directly attributable to behaviour due to opioid intoxication on the part of the person to whom the diagnosis of single episode of harmful use applies. This diagnosis should not be made if the harm is attributed to a known pattern of opioid use. 

6C43.1 Harmful pattern of use of opioids - A pattern of use of opioids 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. The pattern of opioid use is evident over a period of at least 12 months if substance use is episodic or at least one month if use is continuous (i.e., daily or almost daily). Harm to health of the individual occurs due to one or more of the following: (1) behaviour related to intoxication; (2) direct or secondary toxic effects on body organs and systems; or (3) a harmful route of administration. Harm to health of others includes any form of physical harm, including trauma, or mental disorder that is directly attributable to behaviour related to opioid intoxication on the part of the person to whom the diagnosis of Harmful pattern of use of opioids applies. 

6C45.0 Episode of harmful use of cocaine - An episode of use of cocaine 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; (2) direct or secondary toxic effects on body organs and systems; or (3) a harmful route of administration. Harm to health of others includes any form of physical harm, including trauma, or mental disorder that is directly attributable to behaviour due to cocaine intoxication on the part of the person to whom the diagnosis of single episode of harmful use applies. This diagnosis should not be made if the harm is attributed to a known pattern of cocaine use. 

6C45.1 Harmful pattern of use of cocaine - A pattern of use of cocaine 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. The pattern of cocaine use is evident over a period of at least 12 months if substance use is episodic or at least one month if use is continuous (i.e., daily or almost daily). Harm to health of the individual occurs due to one or more of the following: (1) behaviour related to intoxication; (2) direct or secondary toxic effects on body organs and systems; or (3) a harmful route of administration. Harm to health of others includes any form of physical harm, including trauma, or mental disorder that is directly attributable to behaviour related to cocaine intoxication on the part of the person to whom the diagnosis of Harmful pattern of use of cocaine applies.

See also, from ICD-11

6C48.10 Harmful pattern of use of caffeine, episodic

6C48.11 Harmful pattern of use of caffeine, continuous

6C49.0 Episode of harmful use of hallucinogens

6C49.1 Harmful pattern of use of hallucinogens

6C4A.1 Harmful pattern of use of nicotine

6C4B.0 Episode of harmful use of volatile inhalants

6C4B.1 Harmful pattern of use of volatile inhalants

6C42.0 Episode of harmful use of synthetic cannabinoids

6C42.1 Harmful pattern of use of synthetic cannabinoids

6C47.0 Episode of harmful use of synthetic cathinones

6C47.1 Harmful pattern of use of synthetic cathinones

6C4C.1Z Harmful pattern of use of MDMA or related drugs, including MDA, unspecified

6C4H.0 Episode of harmful use of non-psychoactive substances

6C4H.1 Harmful pattern of use of non-psychoactive substances