# 144 - Harmful pattern of psychoactive substance use

# Harmful pattern of psychoactive substance use

Clinical Descriptions and Diagnostic Requirements for ICD-11 Mental, Behavioural or Neurodevelopmental Disorders
Boundary with substance intoxication
Substance intoxication is defined by substance use that results in clinically significant transient 
substance-specific symptoms (see Table 6.15, p. 475). Recovery from substance intoxication is 
generally complete and without physical or mental sequelae. If there is continuing damage or harm 
(e.g. the effects of hypoxia, the effects of prolonged hyperactivity or inactivity, tissue damage) due 
to an episode of substance intoxication, a diagnosis of episode of harmful psychoactive substance 
use may be assigned. If relevant at the time of the clinical encounter (e.g. in emergency settings), 
episode of harmful psychoactive substance use may be diagnosed with an associated diagnosis of 
substance intoxication.
Boundary with substance-induced mental disorders
Substance-induced mental disorders can be associated with a single episode of substance use. 
If a substance-induced mental disorder has occurred as a form of harm resulting from a single 
episode of substance use, both episode of harmful psychoactive substance use and the relevant 
substance-induced mental disorder should be diagnosed (e.g. episode of harmful cocaine use 
with cocaine-induced psychotic disorder). Note: specific substance-induced mental disorders are 
only applicable for some substances or substance classes (see Table 6.14, p. 454).
Boundary with overdose
When ingestion of psychoactive substances results in symptoms of overdose (e.g. coma, lifethreatening cardiac or respiratory suppression), a diagnosis from the grouping of harmful effects 
of substances in Chapter 22 on injury, poisoning or certain other consequences of external causes 
should also be assigned.
Harmful pattern of psychoactive substance use
Available categories by substance class
6C40.1 
Harmful pattern of use of alcohol
6C41.1 
Harmful pattern of use of cannabis
6C42.1 
Harmful pattern of use of synthetic cannabinoids
6C43.1 
Harmful pattern of use of opioids
6C44.1 
Harmful pattern of use of sedatives, hypnotics or anxiolytics
6C45.1 
Harmful pattern of use of cocaine
6C46.1 
Harmful pattern of use of stimulants, including amfetamines, methamfetamine 
and methcathinone
6C47.1 
Harmful pattern of use of synthetic cathinones
6C48.1 
Harmful pattern of use of caffeine
6C49.1 
Harmful pattern of use of hallucinogens
6C4A.1 
Harmful pattern of use of nicotine
6C4B.1 
Harmful pattern of use of volatile inhalants
6C4C.1 
Harmful pattern of use of MDMA or related drugs, including MDA
6C4D.1 
Harmful pattern of use of dissociative drugs, including ketamine and PCP
6C4E.1 
Harmful pattern of use of other specified psychoactive substance
6C4F.1 
Harmful pattern of use of multiple specified psychoactive substances
6C4G.1 
Harmful pattern of use of unknown or unspecified psychoactive substances
Diagnostic requirements for disorders due to substance use | Harmful pattern of psychoactive substance use

459
Disorders due to substance use or addictive behaviours
Essential (required) features
• A pattern of continuous, recurrent or sporadic use of a psychoactive substance that has 
caused clinically significant damage to a person’s physical health (e.g. bloodborne infection 
from intravenous self-administration) or mental health (e.g. substance-induced mood 
disorder), or has resulted in behaviour leading to harm to the health of others is required 
for diagnosis.
• Harm to the health of the individual occurs due to one or more of the following: behaviour 
related to intoxication (see Table 6.15, p. 475); direct or secondary toxic effects on body 
organs and systems; or a harmful route of administration.
• Harm to the health of others includes any form of physical harm, including trauma, or 
mental disorder that is directly attributable to behaviour related to substance intoxication 
on the part of the person to whom the diagnosis of harmful pattern of psychoactive 
substance use applies.
• The pattern of use of the relevant substance is evident over a period of at least 12 months if 
substance use is episodic, or at least 1 month if use is continuous.
• The harm to health is not better accounted for by another medical condition or another 
mental disorder, including another disorder due to substance use (e.g. substance 
withdrawal).
Note: harm to the health of the person to whom the diagnosis applies includes injuries caused by 
behaviour related to intoxication (e.g. impulsive aggressive behaviour, psychomotor impairment 
leading to injury; see Table 6.15, p. 475); acute health problems resulting from substance use 
(e.g. overdose, acute gastritis, the effects of hypoxia or prolonged hyperactivity or inactivity), and 
exacerbation or decompensation of pre-existing chronic health problems (e.g. hypertension, liver 
disease, or peptic ulceration). Harm may also result from a harmful route of administration (e.g. 
injecting drug use causing bloodborne virus infections, cocaine use causing a perforated nasal 
septum). The relevant diagnostic codes from other ICD-11 chapters – including Chapter 22 on 
injury, poisoning or certain other consequences of external causes – should be used to describe 
the specific health consequences of the harmful substance use.
Harm to the health of others includes any form of physical harm, including trauma (e.g. impaired 
driving causing a motor vehicle accident, assaultive behaviour leading to bodily harm to another 
person) or mental disorder (e.g. post-traumatic stress disorder arising from an assault by the 
intoxicated individual) that is directly attributable to behaviour due to substance intoxication 
on the part of the person to whom the diagnosis of harmful pattern of psychoactive substance 
use applies.
Diagnostic requirements for disorders due to substance use | Harmful pattern of psychoactive substance use

Clinical Descriptions and Diagnostic Requirements for ICD-11 Mental, Behavioural or Neurodevelopmental Disorders
Course specifiers
A specifier is used to further describe the harmful pattern of substance use, using a fifth-character 
code. The x below corresponds to the fourth-character code indicating the substance class (0 for 
alcohol, 1 for cannabis, 2 for synthetic cannabinoids and so on).
Harmful pattern of psychoactive substance use, episodic
This category is assigned when all the diagnostic requirements for harmful pattern of psychoactive 
substance use are met, and there is evidence of a pattern of recurrent episodic or intermittent 
use of the relevant psychoactive substance over a period of at least 12 months that has caused 
clinically significant harm to a person’s physical or mental health or has resulted in behaviour 
leading to harm to the health of others.
Harmful pattern of psychoactive substance use, continuous
This category is assigned when all the diagnostic requirements for harmful pattern of psychoactive 
substance use are met, and there is evidence of a pattern of continuous substance use (daily 
or almost daily) of the relevant psychoactive substance over a period of at least 1 month that 
has caused clinically significant harm to a person’s physical or mental health or has resulted in 
behaviour leading to harm to the health of others.
Harmful pattern of psychoactive substance use, unspecified
Additional clinical features
• There must be explicit evidence of harm to the individual’s physical or mental health, or 
of behaviour due to substance intoxication that has led to harm to the physical or mental 
health of others. There must also be a clear causal relationship between the harm to health 
and the episodic or continuous use of a substance.
• The likelihood of harm to self or others due behaviour related to intoxication varies 
substantially by substance (see Table 6.15, p. 475). For example, such behaviour is unlikely 
to arise from caffeine or nicotine intoxication.
• A diagnosis of harmful pattern of use of unknown or unspecified psychoactive substances 
can be assigned if the substance consumed is initially unknown. As more information 
becomes available (e.g. laboratory results, report from a collateral informant) the diagnosis 
should be changed to indicate the substance(s) involved in the harmful pattern of 
psychoactive substance use.
• As more information becomes available about symptoms and behaviours related to the 
pattern of substance use, as well as physiological features indicative of neuroadaptation 
6C4x.10
6C4x.11
6C4x.1Z
Diagnostic requirements for disorders due to substance use | Harmful pattern of psychoactive substance use

461
Disorders due to substance use or addictive behaviours
to the substance, the diagnosis may be changed to substance dependence if diagnostic 
requirements are met.
Boundary with normality (threshold)
• The diagnosis of harmful pattern of psychoactive substance use requires clinically significant 
harm to the individual’s physical or mental health or the health of others. Examples of 
impact on physical or mental health that would not be considered clinically significant 
include mild hangovers, brief episodes of vomiting, or transient depressed mood.
• A pattern of psychoactive substance use may cause a range of problems in functioning 
(e.g. missed appointments, arguments with loved ones) that are not sufficiently severe to 
constitute clinically significant harm to physical or mental health. Such problems are not a 
sufficient basis for a diagnosis of harmful pattern of psychoactive substance use.
Developmental presentations
• Harmful pattern of psychoactive substance use is often a characteristic of late adolescence 
and young adulthood, and injuries and the consequences of aggressive behaviour are 
particularly common in this age group.
• Harmful pattern of psychoactive substance use in older adults may cause injuries and 
fractures due to the combination of lowered tolerance, psychomotor impairment induced 
by a substance, and disorders associated with ageing such as osteoporosis and dementia.
Sex- and/or gender-related features
• The prevalence of harmful pattern of psychoactive substance use is higher in males, but 
the gender differential is smaller in countries where women play a greater role in the 
workforce. Gender differences in injuries and other forms of harm due to substance use 
are recognized.
Boundaries with other disorders and conditions (differential diagnosis)
Boundary with hazardous substance use
Hazardous substance use is classified in Chapter 24 on factors influencing health status or contact 
with health services and not in this chapter on mental, behavioural and neurodevelopmental 
disorders. hazardous substance use appreciably increases the risk of harmful physical or mental 
health consequences, to the user or to others, to an extent that warrants attention and advice from 
Diagnostic requirements for disorders due to substance use | Harmful pattern of psychoactive substance use

Clinical Descriptions and Diagnostic Requirements for ICD-11 Mental, Behavioural or Neurodevelopmental Disorders
health professionals, but has not resulted in specific identifiable harm and therefore does not meet 
the diagnostic requirements for harmful pattern of psychoactive substance use.
Boundary with episode of harmful psychoactive substance use
If the harm to health is a result of a single episode of use rather than a pattern of substance use, 
whether episodic or continuous, a diagnosis of episode of harmful psychoactive substance use 
should be assigned. Substance use is generally considered to be following a pattern if there has 
been at least episodic or intermittent use over a period of at least 12 months. If harm is caused by 
use of a substance but no information is available about the pattern or history of substance use, 
a diagnosis of episode of harmful psychoactive substance use may be assigned until such time as 
evidence for a pattern of use is ascertained.
Boundary with substance dependence
In substance dependence, individuals use a substance or substances persistently, despite harm and 
adverse consequences. Harm caused by such use may be similar to that observed in harmful pattern 
of psychoactive substance use. However, substance dependence also includes additional features 
of impaired ability to control use and increasing priority given to the substance use over other 
activities. Physiological features (e.g. tolerance) may also be present for applicable substances. If 
all diagnostic requirements for substance dependence are met for a particular substance, Harmful 
pattern of psychoactive substance use should not be assigned for that substance. Note: substance 
dependence is only applicable for some substances or substance classes (see Table 6.13, p. 450).
Boundary with substance intoxication
Substance intoxication is defined by substance use that results in clinically significantly, transient 
substance-specific symptoms (see Table 6.15, p. 475). Recovery from substance intoxication is 
generally complete and absent of physical or mental sequelae. A pattern or repeated intoxication 
may or may not result in harm to a person’s physical or mental health or to the health of others. If 
there is continuing damage or harm (e.g. the effects of hypoxia, the effects of prolonged hyperactivity 
or inactivity, tissue damage) as a result of repeated or continuous use of a psychoactive substance, 
a diagnosis of harmful pattern of psychoactive substance use may be assigned. If relevant at 
the time of the clinical encounter (e.g. in emergency settings), harmful pattern of psychoactive 
substance use may be diagnosed with an associated diagnosis of substance intoxication.
Boundary with substance withdrawal
Substance withdrawal occurs upon cessation or reduction of a substance in the context of 
physiological dependence, or when a substance has been taken for a prolonged period or in 
large amounts. Some features of substance withdrawal may include physical or mental harm 
(e.g. seizures, delusions, hallucinations, anxiety). If the symptoms are entirely explained by the 
withdrawal syndrome for the relevant substance (see Table 6.16, p. 484), an additional diagnosis 
of harmful pattern of psychoactive substance use is not warranted. However, if the symptoms 
substantially exceed the expected withdrawal syndrome in duration or type or severity, and the 
diagnostic requirements for substance dependence are not met, harmful pattern of psychoactive 
substance use can be assigned as the primary diagnosis, with an associated diagnosis of substance 
withdrawal (e.g. harmful pattern of use of opioids with opioid withdrawal). Note: substance 
withdrawal is only applicable for some substances or substance classes (see Table 6.13, p. 450).
Boundary with substance-induced mental disorders
If a substance-induced mental disorder has occurred as a form of harm resulting from a pattern 
of substance use, both harmful pattern of psychoactive substance use and the relevant substanceinduced mental disorder should be diagnosed (e.g. harmful pattern of cocaine use with cocaineinduced anxiety disorder). Note: specific substance-induced mental disorders are only applicable 
for some substances or substance classes (see Table 6.14, p. 454).
Diagnostic requirements for disorders due to substance use | Harmful pattern of psychoactive substance use