In general, to be considered a substance/medication—induced mental disorder, there must be evidence that the disorder being observed is not likely to be better explained by an independent mental condition. The latter are most likely to be seen if the mental disorder was present before the severe intoxication or withdrawal or medication administration, or, with the exception of several substance—induced persisting disorders listed in Table 1, con- tinued more than 1 month after cessation of acute withdrawal, severe intoxication, or use of the medications. When symptoms are only observed during a delirium (e.g., alcohol withdrawal delirium), the mental disorder should be diagnosed as a delirium, and the psychiatric syndrome occurring during the delirium should not also be diagnosed sepa- rately, as many symptoms (including disturbances in mood, anxiety, and reality testing) are commonly seen during agitated, confused states. The features associated with each rel- evant major mental disorder are similar whether observed with independent or sub- stance/medication-induced mental disorders. However, individuals with substance/ medication-induced mental disorders are likely to also demonstrate the associated fea- tures seen with the specific category of substance or medication, as listed in other subsec- tions of this chapter.
Substance-induced mental disorders develop in the context of intoxication or withdrawal from substances of abuse, and medication-induced mental disorders are seen with pre- scribed or over-the-counter medications that are taken at the suggested doses. Both condi- tions are usually temporary and likely to disappear within 1 month or so of cessation of acute withdrawal, severe intoxication, or use of the medication. Exceptions to these generaliza- tions occur for certain long-duration substance-induced disorders: substance-associated neurocognitive disorders that relate to conditions such as alcohol-induced neurocognitive disorder, inhalant-induced neurocognitive disorder, and sedative-, hypnotic-, or anxiolytic- backs"; see the section "Hallucinogen-Related Disorders” later in this chapter). However, most other substance/ medication-induced mental disorders, regardless of the severity of the symptoms, are likely to improve relatively quickly with abstinence and unlikely to re- main clinically relevant for more than 1 month after complete cessation of use.
As is true of many consequences of heavy substance use, some individuals are more and others less prone toward specific substance-induced disorders. Similar types of pre— dispositions may make some individuals more likely to develop psychiatric side effects of some types of medications, but not others. However, it is unclear whether individuals with family histories or personal prior histories with independent psychiatric syndromes are more likely to develop the induced syndrome once the consideration is made as to whether the quantity and frequency of the substance was sufficient to lead to the devel- opment of a substance-induced syndrome.
There are indications that the intake of substances of abuse or some medications with psychiatric side effects in the context of a preexisting mental disorder is likely to result in an intensification of the preexisting independent syndrome. The risk for substance/med- ication—induced mental disorders is likely to increase with both the quantity and the fre- quency of consumption of the relevant substance.
The symptom profiles for the substance/medication-induced mental disorders resem- ble independent mental disorders. While the symptoms of substance/medication-in- duced mental disorders can be identical to those of independent mental disorders (e.g., delusions, hallucinations, psychoses, major depressive episodes, anxiety syndromes), and although they can have the same severe consequences (e.g., suicide), most induced mental disorders are likely to improve in a matter of days to weeks of abstinence.