[3] Some common combinations that are used recreationally include Some substances, such as the powerful psychedelic drug DMT, are not psychoactive when ingested alone.

This cumulative effect can lead to further unintended harm to health dependent on what is being covertly added.

Concerns exist about a number of pharmacological pairings, especially: Within the general concept of multiple drug use, several specific meanings of the term must be considered.

On the other hand, the use of several substances in an intensive and chaotic way, simultaneously or consecutively, in many cases each drug substituting for another according to availability.

[12] A study among treatment admissions found that it is more common for younger people to report polysubstance use.