{"id":7367,"date":"2011-01-24T14:53:03","date_gmt":"2011-01-24T14:53:03","guid":{"rendered":"https:\/\/drugprevent.org.uk\/ppp\/?p=7367"},"modified":"2011-01-24T14:53:03","modified_gmt":"2011-01-24T14:53:03","slug":"high-potency-cannabis-and-the-risk-of-psychosis","status":"publish","type":"post","link":"https:\/\/drugprevent.org.uk\/ppp\/2011\/01\/high-potency-cannabis-and-the-risk-of-psychosis\/","title":{"rendered":"High-potency cannabis and the risk of psychosis"},"content":{"rendered":"

During the last quarter of the 20th century recreational use of
\ncannabis increased greatly across the world.1 Cannabis consumption
\ncame to be seen as a normal leisure activity, and was regarded
\nas safe even by the medical establishment.2 However, in recent
\nyears there has been considerable controversy over the use of
\ncannabis, with, for example, the UK government repeatedly
\nreviewing its safety.3 This concern has arisen from large prospective
\nepidemiological studies which have reported that use of
\ncannabis increases the risk of schizophrenia-like psychosis.4,5
\nHowever, these studies have not collected detailed data on the
\npatterns of use or potency of the cannabis used, which may be
\nimportant factors moderating the associated risk.6
\nThe principal constituents of cannabis are D9-tetrahydrocannabinol
\n(D9-THC) and cannabidiol. The former is the main
\npsychoactive ingredient and in experimental studies it produces
\ntransient psychotic symptoms and impaired memory in a dose dependent
\nmanner.6,7 In contrast, cannabidiol does not induce
\nhallucinations or delusions, and it seems to antagonise the cognitive
\nimpairment and psychotogenic effects caused by D9-THC.6
\nUntil the early 2000s the most freely available type of cannabis
\nin the UK was cannabis resin (\u2018hash\u2019), which had approximately
\n70% of the \u2018street\u2019 market, followed by traditional imported herbal
\ncannabis and then sinsemilla (\u2018skunk\u2019). Cannabis resin contains
\n2\u20134% D9-THC and a similar proportion of cannabidiol, whereas
\nherbal cannabis contains a similar percentage of D9-THC but no
\ncannabidiol.8,9 However, sinsemilla (skunk) has increasingly taken
\nover the UK market and its THC concentration, and to a lesser
\nextent that of imported herbal cannabis, has been consistently
\nrising. For example, seizures of cannabis on the streets of England
\nin 2008 by the police showed that sinsemilla had a market share
\nof more than 70%, and had reached a D9-THC concentration of
\n12\u201318% with virtually no cannabidiol.8,9<\/p>\n

Smith has suggested that such high-potency cannabis might be
\nespecially harmful to mental health.10 We therefore compared
\npatterns and types of cannabis use in people experiencing their
\nfirst episode of psychosis and in a healthy control sample.
\nSpecifically, we sought to test the hypothesis that daily use of
\nhigh-potency cannabis is associated with a particularly high risk
\nof psychosis.<\/p>\n

Method<\/strong>
\nSample
\nWe approached all patients aged 18\u201365 years who presented with a
\nfirst episode of psychosis to the Lambeth, Southwark and Croydon
\nadult in-patient units of the South London & Maudsley Mental
\nHealth National Health Service (NHS) Foundation Trust between
\nDecember 2005 and October 2008. We validated clinical diagnosis
\nby administering the Schedules for Clinical Assessment in
\nNeuropsychiatry (SCAN).11 Patients who met ICD\u201310 criteria
\nfor a diagnosis of psychosis (codes F20\u2013F29 and F30\u2013F33)12 were
\ninvited to participate in the study; cases with a diagnosis of
\norganic psychosis were excluded. During the same period we
\nrecruited a healthy control group (n = 174) from the local
\npopulation living in the area served by the Trust, by means of
\ninternet and newspaper advertisements, and distribution of
\nleaflets at train stations, shops and job centres. Cannabis was
\nnot mentioned in these advertisements. Particular attention was
\ndirected to attempting to obtain a control sample similar to the
\npatient sample in age, gender, ethnicity, educational qualifications
\nand employment status. Those who agreed to participate were
\nadministered the Psychosis Screening Questionnaire,13 and
\nexcluded if they met criteria for a psychotic disorder or reported
\na previous diagnosis of psychotic illness.
\nEthical permission was obtained from the Trust and the
\nInstitute of Psychiatry research ethics committee. All study
\nparticipants signed a consent form allowing publication of data
\noriginating from the study.<\/p>\n

Background<\/strong>
\nPeople who use cannabis have an increased risk of
\npsychosis, an effect attributed to the active ingredient D9-
\ntetrahydrocannabinol (D9-THC). There has recently been
\nconcern over an increase in the concentration of D9-THC in
\nthe cannabis available in many countries.<\/p>\n

Aims
\n<\/strong>To investigate whether people with a first episode of
\npsychosis were particularly likely to use high-potency
\ncannabis.<\/p>\n

Method<\/strong>
\nWe collected information on cannabis use from 280 cases
\npresenting with a first episode of psychosis to the South
\nLondon & Maudsley National Health Service (NHS) Foundation
\nTrust, and from 174 healthy controls recruited from the local
\npopulation.<\/p>\n

Results<\/strong>
\nThere was no significant difference between cases and
\ncontrols in whether they had ever taken cannabis, or age at
\nfirst use. However, those in the cases group were more
\nlikely to be current daily users (OR = 6.4) and to have smoked
\ncannabis for more than 5 years (OR = 2.1). Among those who
\nused cannabis, 78% of the cases group used high-potency
\ncannabis (sinsemilla, \u2018skunk\u2019) compared with 37% of the
\ncontrol group (OR 6.8).<\/p>\n

Conclusions<\/strong>
\nThe finding that people with a first episode of psychosis had
\nsmoked higher-potency cannabis, for longer and with greater
\nfrequency, than a healthy control group is consistent with
\nthe hypothesis that D9-THC is the active ingredient
\nincreasing risk of psychosis. This has important public health
\nimplications, given the increased availability and use of highpotency
\ncannabis.<\/p>\n

Source: The British Journal of Psychiatry (2009)
\n195, 488\u2013491. doi: 10.1192\/bjp.bp.109.064220<\/em><\/p>\n

<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

During the last quarter of the 20th century recreational use of cannabis increased greatly across the world.1 Cannabis consumption came to be seen as a normal leisure activity, and was regarded as safe even by the medical establishment.2 However, in recent years there has been considerable controversy over the use of cannabis, with, for example, […]<\/p>\n","protected":false},"author":4,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[22],"tags":[],"class_list":["post-7367","post","type-post","status-publish","format-standard","hentry","category-effects-of-drugs-papers"],"_links":{"self":[{"href":"https:\/\/drugprevent.org.uk\/ppp\/wp-json\/wp\/v2\/posts\/7367","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/drugprevent.org.uk\/ppp\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/drugprevent.org.uk\/ppp\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/drugprevent.org.uk\/ppp\/wp-json\/wp\/v2\/users\/4"}],"replies":[{"embeddable":true,"href":"https:\/\/drugprevent.org.uk\/ppp\/wp-json\/wp\/v2\/comments?post=7367"}],"version-history":[{"count":0,"href":"https:\/\/drugprevent.org.uk\/ppp\/wp-json\/wp\/v2\/posts\/7367\/revisions"}],"wp:attachment":[{"href":"https:\/\/drugprevent.org.uk\/ppp\/wp-json\/wp\/v2\/media?parent=7367"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/drugprevent.org.uk\/ppp\/wp-json\/wp\/v2\/categories?post=7367"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/drugprevent.org.uk\/ppp\/wp-json\/wp\/v2\/tags?post=7367"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}