Cannabis-Caused Delirium (Acute Confusional State)


Cannabis smoking can cause an acute and short-lasting (between a few hours and a few days) state of profound delirium. The individuals affected experience complete or partial loss of their orientational ability, their memory and their sense of their own identity. An element of delirium is a common occurrence in cannabis psychosis.

This condition is probably more likely to arise if high doses of THC are involved or if the individual is in a weakened condition, for example owing to lack of sleep or to withdrawal symptoms relating to alcohol or other drugs.

Certain experts have calculated that delirium or cannabis psychosis occurs at one time or another in 10 per cent of all cannabis abusers.

There is widespread agreement that the use of cannabis, especially in high doses, can cause delirium (), which is also known as acute brain syndrome or delirium. This is a short-lived condition, lasting from a few hours up to a few days. One characteristic of this condition is unclear consciousness: the persons affected have difficulty with spatial and temporal orientation, are unable to perceive correctly the situation in which they find themselves, and may fail to recognise close acquaintances. Not infrequently, this condition is difficult to distinguish from cannabis psychosis, which is described in the next chapter; and indeed it is not unlikely that one quite often encounters conditions which are a mix of delirium and cannabis psychosis. Castle and Ames (1996) subsume all transient confusional states, cannabis psychoses and psychosis-like conditions under the heading “acute brain syndromes” (or “encephalopathies”).

The main feature is profound confusion with regard to space, time, place and the people nearby, as well as uncertainty with regard to one’s own identity. Misjudgements of sense impressions and memory disturbance may also occur, as well as language disturbances (such as incoherent speech). Dramatic and rapid shifts in mental state are not unusual. There may also appear, in varying degrees, genuinely psychotic symptoms such as delusions and hallucinations.

In all probability, the degree of intoxication is important in determining whether or not this condition is provoked. Holister (1986) is one of the researchers who claim that this explains why cannabis-induced delirium was significantly more common outside North America in the mid-1980s, what with marijuana being the predominant cannabis preparation in Canada and the United States while hashish was (as it still is) the more common form in Europe.

The condition is probably more likely to be provoked in persons who are in a physically weakened state for a variety of reasons, such as physical illness, malnourishment, severe sleeplessness, the effects of other drugs or withdrawal symptoms.

The symptoms are frightening both to the individual and to those who witness them. Since a completely disoriented person may sometimes perform actions which are based on a totally erroneous perception of the surrounding reality, the condition can be serious and place the individual in dangerous – on occasion even fatal – situations. Under the heading “Cannabis and Suicide”, I account for a Swedish study of deaths caused by jumping from a height while under the influence of cannabis. In at least one of the cases reported, I have been able to conclude, by examining medical records, police reports and other material, that the suicide was carried out under the influence of severe disorientation/confusion, even though a (non-depressive) psychosis was present at the same time.

As has previously been mentioned, it is very difficult to calculate how likely cannabis abusers are to be affected by a given harmful effect. Based on general clinical experience as well as reports by abusers and their families, however, cannabis psychosis/delirium would seem to be a not entirely infrequent side-effect.

Selections from the book: “Adverse Health Consequences of Cannabis Use. A Survey of Scientific Studies Published up to and including the Autumn of 2003