The Report of the National Commission on Marihuana and Drug Abuse

Effects of Long-Term Cannabis Use

RECURRENT PHENOMENON

Another poorly understood phenomenon is the spontaneous recurrence of all or part of the drug intoxicated state (somatic and visual sensations) when not under the influence of the drug. This phenomenon has been called a "flashback" when it occurs spontaneously or "a contact high" when it occurs in the presence of others who are intoxicated.

Flashbacks have been reported with marihuana use alone. However, these occurrences are apparently predominant in marihuana users, who have taken hallucinogenic drugs previously. These marihuana, users occasionally find that marihuana highs change for them after their hallucinogenic. experiences. For example, a simple hallucination experienced previously may reoccur while high on marihuana.

These flashbacks may be interpreted as pleasant, even desired experiences by some but unwelcome and disturbing to others. The recurrences are benign in most individuals and tend to disappear as the hallucinogenic experience recedes in time (Keeler, 1967; Smith, 1968; Weil, 1970; Bialos, 1970; Blumenfield, 1970).

Truly vivid experiences which recapture most of the elements of the original experience are extremely rare (Smith and Meld, 1970). More often they resemble an anxiety state occurring after an unpleasant high or the recurrence of a new perceptual awareness gained while high. It is difficult to differentiate these recurrences from the not uncommon deja vu phenomenon in which a person has the illusion that a perceived situation has occurred before. These recurrences are intermittent and usually occur within a few days to weeks following the use of marihuana.