Because of increased access to nitrous oxide (”laughing gas"), membership in certain populations is associated with diagnosis of nitrous oxide use disorder. The role of this gas as an anesthetic agent leads to misuse by some medical and dental professionals. Its use as a propellant for commercial products (e.g., whipped cream dispensers) contributes to misuse by food service workers. With recent widespread availability of the substance in ”Whippet” cartridges for use in home whipped cream dispensers, nitrous oxide misuse by adolescents and young adults is significant, especially among those who also inhale vola- tile hydrocarbons. Some continuously using individuals, inhaling from as many as 240 whippets per day, may present with serious medical complications and mental conditions, including myeloneuropathy, spinal cord subacute combined degeneration, peripheral neuropathy, and psychosis. These conditions are also associated with a diagnosis of ni- trous oxide use disorder.
Use of amyl-, butyl-, and isobutyl nitrite gases has been observed among homosexual men and some adolescents, especially those with conduct disorder. Membership in these populations may be associated with a diagnosis of amy1—, butyl-, or isobutyl—nitrite use dis- order. However, it has not been determined that these substances produce a substance use disorder. Despite tolerance, these gases may not alter behavior through central effects, and they may be used only for their peripheral effects.
Substance use disorders generally are associated with elevated risks of suicide, but there is no evidence of unique risk factors for suicide with other (or unknown) substance use disorder.
Based on extremely limited data, the prevalence of other (or unknown) substance use disorder is likely lower than that of use disorders involving the nine substance classes in this chapter.
No single pattern of development or course characterizes the pharmacologically varied other (or unknown) substance use disorders. Often unknown substance use disorders will be reclassified when the unknown substance eventually is identified.
Risk and prognostic factors for other (or unknown) substance use disorders are thought to be similar to those for most substance use disorders and include the presence of any other substance use disorders, conduct disorder, or antisocial personality disorder in the indi- vidual or the individual’s family; early onset of substance problems; easy availability of the substance in the individual’s environment; childhood maltreatment or trauma; and ev- idence of limited early self—control and behavioral disinhibition.
Certain cultures may be associated with other (or unknown) substance use disorders in- volving specific indigenous substances within the cultural region, such as betel nut.
Urine, breath, or saliva tests may correctly identify a commonly used substance falsely sold as a novel product. However, routine clinical tests usually cannot identify truly un- usual or new substances, which may require testing in specialized laboratories.
Use of other or unknown substances without meeting criteria for other (or unknown) substance use disorder. Use of unknown substances is not rare among adolescents, but most use does not meet the diagnostic standard of two or more criteria for other (or un- known) substance use disorder in the past year.
Substance use disorders. Other (or unknown) substance use disorder may co—occur with various substance use disorders, and the symptoms of the disorders may be similar and overlapping. To disentangle symptom patterns, it is helpful to inquire about which symptoms persisted during periods when some of the substances were not being used.
Other (or unknown) substance/medication-induced disorder. This diagnosis should be differentiated from instances when the individual’s symptoms meet full criteria for one of the following disorders, and that disorder is caused by an other or unknown substance: delirium, major or mild neurocognitive disorder, psychotic disorder, depressive disorder, anxiety disorder, sexual dysfunction, or sleep disorder.