Abstract:
The October 2020 ‘reeferendum’ will determine
the legal status of recreational
cannabis in New Zealand (http://www.
referendums.govt.nz/cannabis/summary.
html). Amidst the many arguments for and
against, a key issue has yet to receive adequate
debate and critical scrutiny. Cannabis-
induced psychosis warrants concern
because of the profound and sometimes
irreversible social and occupational disability
that can result. Epidemiological data from
New Zealand1 and elsewhere2,3 strongly
implicate a causal role for tetrahydrocannabinol
(THC) in schizophrenia. Additional
concern arises from the impacts of regular
cannabis use on a critical period of brain
maturation during adolescence up to the age
of 25 or so.4
These problems are exacerbated by
commercial pressure, regardless of
legal status, for producers to develop
strains of cannabis with ever higher THC
content. Urban myths notwithstanding,
THC drives recreational use as well as
reported symptom relief and side-effects
of ‘medicinal’ cannabis.5 Another cannabis
constituent, cannabidiol (CBD), may mitigate
the psychotogenicity of THC,6 but the
notion that suffi ciently high levels of the
former relative to the latter could be legally
mandated must be regarded as little more
than a pipe dream.7
If recreational cannabis were to be
legalised in New Zealand, based on overseas
experience we can expect rapid commercialisation,
increased use in the adult and
adolescent populations, followed by an
elevated incidence of psychosis.3 A proper
health-economic study will be required to
reckon the consequent social and economic
costs and, ideally, to counterbalance these
against anticipated gains from legalisation
on reduced gang activity, prosecution and
incarceration.8 On the other hand, there is
evidence that decriminalisation9 offers a
useful compromise between the extremes of
legalisation and criminalisation; its relevance
as an alternative in New Zealand
has been cogently argued,10 but available
evidence indicates that we still have a long
way to go to achieve this.11,12