Memory lessening was the only significant reported
side effect among the prolonged users. Neuropsychological
decline is well known to result from prolonged time and
persistent cannabis use, as was reported in the Dunedin
Study, for example, a prospective study of a birth cohort of
individuals followed from birth to age of 38 years [8]. Also
in the short term, cannabis use can cause a modest effect
on self-reported problems with prospective memory, with
a primary problem with retrospective memory appearing
to underlie this relationship, as was found in a prospective
study with healthy individuals [9]. The significant memory
lessening in the current study may be related to additive or
synergistic influences of comedications, such as opioids and
antidepressive drugs, or to the older age of most of the users,
compared to the usual study population of cannabis users.
Further research to clarify this point is needed.
The population of the prolonged users in the current
study reported significant improvement in all aspects of supportive
and palliative oncology care. This group of patients
represents unselected symptomatic cancer patients, and the
results are mainly based on patients self-reports during the
interviews. The results from prospective randomized trials
on different cannabinoids were less significant. Clinical trials
conducted on the effect ofmedicinal cannabis on pain reduction
in cancer patients were either negative or inconclusive.
It should be noted that these research projects included
a small number of participants, and some were observational
[2, 10]. Recently, a randomized, double-blind, placebocontrolled,
graded-dose study in patients with advanced
cancer and opioid-refractory pain receiving placebo or nabiximols
showed efficacy in reducing the average daily pain from
baseline and reduction in sleep disruptions. Those effects
were seenmainly in the groups treated with low andmedium
doses [11].