Cannabis use and transition to psychosis in people at ultra-high risk. Effects of continuation, frequency, and type of cannabis use on relapse in the first 2 years after onset of psychosis: an observational study. The temporal dynamics of relationships between cannabis, psychosis and depression among young adults with psychotic disorders: findings from a 10-month prospective study. The impact of substance use on brain structure in people at high risk of developing schizophrenia. Cannabis use and risk of schizophrenia: a Mendelian randomization study Course of cannabis use and clinical outcome in patients with non-affective psychosis: a 3-year follow-up study. The impact of cannabis use on clinical outcomes in recent onset psychosis. Cannabis use in adolescence and risk for adult psychosis: longitudinal prospective study Does change in cannabis use in established psychosis affect clinical outcome? GWAS of lifetime cannabis use reveals new risk loci, genetic overlap with psychiatric traits, and a causal effect of schizophrenia liability Are deficits in cognition associated with psychotic-like experiences after cannabis? A phase-specific psychological therapy for people with problematic cannabis use following a first episode of psychosis: a randomized controlled trial. Continued cannabis use and outcome in first-episode psychosis: data from a randomized, open-label, controlled trial. Motivational Intervention to Reduce Cannabis Use in Young People with Psychosis: A Randomized Controlled Trial Cannabis ‘dependence’ and attentional bias for cannabis-related words Efficacy, tolerability and safety of cannabis‐based medicines for chronic pain management – An overview of systematic reviews Continued cannabis use and risk of incidence and persistence of psychotic symptoms: 10 year follow-up cohort study Motives for cannabis use in high-risk adolescent users. Effects of cannabis use status on cognitive function, in males with schizophrenia Real-world memory and executive processes in cannabis users and non-users Is cannabis an anti-antipsychotic? The experience in psychiatric intensive care. Mechanisms Underlying the Link between Cannabis Use and Prospective Memory Developmental sensitivity to cannabis use patterns and risk for major depressive disorder in mid-life: findings from 40 years of follow-up.
BACKGROUND Cannabis use is associated with an increased risk of developing a psychotic disorder but the temporal relationship between cannabis use and onset of illness is unclear . The objective of this study was to assess prospect ively the influence of cannabis use on transition to psychosis in people at ultra-high risk ( UHR ) for the disorder . METHOD Lifetime and continued cannabis use was assessed in a consecutively ascertained sample of 182 people ( 104 male , 78 female ) at UHR for psychosis . Individuals were then followed clinical ly for 2 years to determine their clinical outcomes . RESULTS Lifetime cannabis use was reported by 134 individuals ( 73.6 % ) . However , most of these individuals had stopped using cannabis before clinical presentation ( n=98 , 73.1 % ) , usually because of adverse effects . Among lifetime users , frequent use , early-onset use and continued use after presentation were all associated with an increase in transition to psychosis . Transition to psychosis was highest among those who started using cannabis before the age of 15 years and went on to use frequently ( frequent early-onset use : 25 % ; infrequent or late-onset use : 5 % ; χ(2)1=10.971 , p=0.001 ) . However , within the whole sample , cannabis users were no more likely to develop psychosis than those who had never used cannabis ( cannabis use : 12.7 % ; no use : 18.8 % ; χ(2)1=1.061 , p=0.303 ) . CONCLUSIONS In people at UHR for psychosis , lifetime cannabis use was common but not related to outcome . Among cannabis users , frequent use , early-onset use and continued use after clinical presentation were associated with transition to psychosis BACKGROUND Although cannabis use after a first episode of psychosis has been associated with relapse , little is known about the determinants of this most preventable risk factor for relapse of psychosis . Here we aim ed to study whether the effects on outcome vary depending on the type of cannabis consumed and usage pattern . METHODS In this observational study , we prospect ively recruited and followed up patients aged 18 - 65 years who presented with their first episode of psychosis to psychiatric services in south London , London , UK .  Relapse of psychosis within 2 years after onset of psychosis was defined as risk of subsequent admission to hospital . We classified patients into different patterns of cannabis use based on continuity of use after onset of psychosis , potency of cannabis consumed , and frequency of use after the onset of their illness . We used multiple regression analyses ( logistic or binominal ) to compare the different cannabis use groups and propensity score analysis to vali date the results . FINDINGS Between April 12 , 2002 , and July 26 , 2013 , 256 patients presented with a first episode of psychosis . We did follow-up assessment s for these patients until September , 2015 . Simple analyses showed that former regular users of cannabis who stopped after the onset of psychosis had the most favourable illness course with regards to relapse . In multiple analysis , continued high-frequency users ( ie , daily use in all 24 months ) of high-potency ( skunk-like ) cannabis had the worst outcome , indexed as an increased risk for a subsequent relapse ( odds ratio [ OR ] 3·28 ; 95 % CI 1·22 - 9·18 ) , more relapses ( incidence rate ratio 1·77 ; 95 % CI 0·96 - 3·25 ) , fewer months until a relapse occurred ( b -0·22 ; 95 % CI -0·40 to -0·04 ) , and more intense psychiatric care ( OR 3·16 ; 95 % CI 1·26 - 8·09 ) after the onset of psychosis . INTERPRETATION Adverse effects associated with continued use of cannabis after the onset of a first episode of psychosis depend on the specific patterns of use . Possible interventions could focus on persuading cannabis-using patients with psychosis to reduce use or shift to less potent forms of cannabis . FUNDING National Institute for Health Research ( NIHR ) BACKGROUND The aim was to examine the temporal relationships over 10 months between cannabis use and symptoms of psychosis and depression in people with schizophrenia and related disorders . The design was a prospect i ve study of 101 patients with schizophrenia and related disorders who were assessed monthly over 10 months on medication compliance , cannabis and other drug use , symptoms of depression and symptoms of psychosis . METHOD Linear regression methods to assess relationships between cannabis use and symptoms of psychosis and depression while adjusting for serial dependence , medication compliance and other demographic and clinical variables . RESULTS Cannabis use predicted a small but statistically significant increase in symptoms of psychosis , but not depression , after controlling for other differences between cannabis users and non-users . Symptoms of depression and psychosis did not predict cannabis use . CONCLUSION Continued cannabis use by persons with schizophrenia predicts a small increase in psychotic symptom severity but not vice versa Ventricular enlargement and reduced prefrontal volume are consistent findings in schizophrenia . Both are present in first episode subjects and may be detectable before the onset of clinical disorder . Substance misuse is more common in people with schizophrenia and is associated with similar brain abnormalities . We employ a prospect i ve cohort study with nested case control comparison design to investigate the association between substance misuse , brain abnormality , and subsequent schizophrenia . Substance misuse history , imaging data , and clinical information were collected on 147 subjects at high risk of schizophrenia and 36 controls . Regions exhibiting a significant relationship between level of use of alcohol , cannabis or tobacco , and structure volume were identified . Multivariate regression then eluci date d the relationship between level of substance use and structure volumes while accounting for correlations between these variables and correcting for potential confounders . Finally , we established whether substance misuse was associated with later risk of schizophrenia . Increased ventricular volume was associated with alcohol and cannabis use in a dose-dependent manner . Alcohol consumption was associated with reduced frontal lobe volume . Multiple regression analyses found both alcohol and cannabis were significant predictors of these abnormalities when simultaneously entered into the statistical model . Alcohol and cannabis misuse were associated with an increased subsequent risk of schizophrenia . We provide prospect i ve evidence that use of cannabis or alcohol by people at high genetic risk of schizophrenia is associated with brain abnormalities and later risk of psychosis . A family history of schizophrenia may render the brain particularly sensitive to the risk-modifying effects of these substances Cannabis use is observationally associated with an increased risk of schizophrenia  , but whether the relationship is causal is not known . Using a genetic approach , we took 10 independent genetic variants previously identified to associate with cannabis use in 32 330 individuals to determine the nature of the association between cannabis use and risk of schizophrenia . Genetic variants were employed as instruments to recapitulate a r and omized controlled trial involving two groups (  cannabis users vs nonusers ) to estimate the causal effect of cannabis use on risk of schizophrenia  in 34 241 cases and 45 604 controls from predominantly European descent . Genetically-derived estimates were compared with a meta- analysis of observational studies reporting ever use of cannabis and risk of schizophrenia or related disorders . Based on the genetic approach , use of cannabis was associated with increased risk of schizophrenia ( odds ratio ( OR ) of schizophrenia for users vs nonusers of cannabis : 1.37 ; 95 % confidence interval ( CI ) , 1.09–1.67 ; P-value=0.007 ) . The corresponding estimate from observational analysis was 1.43 ( 95 % CI , 1.19–1.67 ; P-value for heterogeneity = 0.76 ) . The genetic markers did not show evidence of pleiotropic effects and accounting for tobacco exposure did not alter the association ( OR of schizophrenia for users vs nonusers of cannabis , adjusted for ever vs never smoker : 1.41 ; 95 % CI , 1.09–1.83 ) . This adds to the substantial evidence base that has previously identified cannabis use to associate with increased risk of schizophrenia , by suggesting that the relationship is causal . Such robust evidence may inform public health messages about cannabis use , especially regarding its potential mental health consequences BACKGROUND Prospect i ve studies on the relationship between course of cannabis use and clinical outcome in patients with non-affective psychotic disorders are inconclusive . The current study examined whether ( 1 ) persistent , recently started , discontinued and non-cannabis-using patients with a psychotic disorder differed with regard to illness outcome at 3-year follow-up , and ( 2 ) whether timing of cannabis discontinuation was associated with course of clinical outcome . METHOD This 3-year follow-up study was part of a multi-center study in the Netherl and s and Belgium ( Genetic Risk and Outcome of Psychosis ; GROUP ) . We used mixed-model analyses to investigate the association between pattern of cannabis use and symptoms , global functioning and psychotic relapse . RESULTS In our sample of 678 patients , we found persistent users to have more positive and general symptoms , worse global functioning and more psychotic relapses compared with non-users and discontinued users [ Positive and Negative Syndrome Scale ( PANSS ) positive , p < 0.001 ; PANSS general , p < 0.001 ; Global Assessment of Functioning ( GAF ) symptoms , p = 0.017 ; GAF disability , p < 0.001 ; relapses , p = 0.038 ] . Patients who started using cannabis after study onset were characterized by worse functioning at baseline and showed an increase in general symptoms ( including depression and anxiety ) at the 3-year follow-up ( p = 0.005 ) . Timing of cannabis discontinuation was not associated with clinical outcome . CONCLUSIONS These findings suggest that cannabis use in patients with a psychotic disorder has a long-lasting negative effect on illness outcome , particularly when persistent . Treatment should focus on discouraging cannabis use BACKGROUND There are inconsistencies in findings as to whether cannabis use has a negative impact on clinical outcomes for people with established psychosis . Effects may be more evident on patients with recent onset psychosis . AIM To investigate the relationship between cannabis use and clinical outcome , including whether change in cannabis use affects psychotic symptoms , affective symptoms , functioning and psychotic relapse in a sample of people in early psychosis with comorbid cannabis abuse or dependence . METHODS One hundred and ten participants were examined prospect ively with repeated measures of substance use antecedent to psychopathology at baseline , 4.5 , 9 , and 18 months . We used r and om intercept models to estimate the effects of cannabis dose on subsequent clinical outcomes and whether change in cannabis use was associated with change in outcomes . RESULTS There was no evidence of a specific association between cannabis use and positive symptoms , or negative symptoms , relapse or hospital admissions . However , a greater dose of cannabis was associated with subsequent higher depression and anxiety . Change in the amount of cannabis used was associated with statistically significant corresponding change in anxiety scores , but not depression . Additionally , reductions in cannabis exposure were related to improved patient functioning . CONCLUSIONS Reducing cannabis may be directly associated with improvements in anxiety and functioning , but not other specific symptoms Papers pp 1195 , 1199 The strongest evidence that cannabis use may be a risk factor for later psychosis  comes from a Swedish cohort study which found that heavy cannabis use at age 18 increased the risk of later schizophrenia sixfold . 1 2 This study could not establish whether adolescent cannabis use was a consequence of pre-existing psychotic symptoms rather than a cause . We present the first prospect i ve longitudinal study of adolescent cannabis use as a risk factor for  adult schizophreniform disorder  , taking into account childhood psychotic symptoms3 antedating cannabis use . View this table : Association between  cannabis use in adolescence and schizophrenia and depressive symptoms and disorders at age 26 ( n=759 ) , controlling for childhood psychotic symptoms and use of other drugs in adolescence The Dunedin multidisciplinary health and development study ( a study of a general population birth cohort of 1037 individuals born in Dunedin , New Zeal and , in 1972 - 3)4 has a 96 % follow up rate at age 26 . It obtained information on psychotic symptoms at age 11 and drug use at ages 15 and 18 from self reports and assessed BACKGROUND Cannabis use has been identified as a potent predictor of the earlier onset of psychosis , but meta- analysis has not indicated that it has a clear effect in established psychosis . AIM To assess the association between cannabis and outcomes , including whether change in cannabis use affects symptoms and functioning , in a large sample of people with established nonaffective psychosis and comorbid substance misuse . METHODS One hundred and sixty participants whose substance use included cannabis were compared with other substance users ( n = 167 ) on baseline demographic , clinical , and substance use variables . The cannabis using subgroup was examined prospect ively with repeated measures of substance use and psychopathology at baseline , 12 months , and 24 months . We used generalized estimating equation models to estimate the effects of cannabis dose on subsequent clinical outcomes and whether change in cannabis use was associated with change in outcomes . RESULTS Cannabis users showed cross-sectional differences from other substances users but not in terms of positive symptoms . Second , cannabis dose was not associated with subsequent severity of positive symptoms and change in cannabis dose did not predict change in positive symptom severity , even when patients became abstinent . However , greater cannabis exposure was associated with worse functioning , albeit with a small effect size . CONCLUSIONS We did not find evidence of an association between cannabis dose and psychotic symptoms , although greater cannabis dose was associated with worse psychosocial functioning , albeit with small effect size . It would seem that within this population , not everyone will demonstrate durable symptomatic improvements from reducing cannabis Cannabis use is a heritable trait that has been associated with adverse mental health outcomes . In the largest genome-wide association study ( GWAS ) for lifetime cannabis use to date ( N = 184,765 ) , we identified eight genome-wide significant independent single nucleotide polymorphisms in six regions . All measured genetic variants combined explained 11 % of the variance . Gene-based tests revealed 35 significant genes in 16 regions , and S-PrediXcan analyses showed that 21 genes had different expression levels for cannabis users versus nonusers . The strongest finding across the different analyses was CADM2 , which has been associated with substance use and risk-taking . Significant genetic correlations were found with 14 of 25 tested substance use and mental health – related traits , including smoking , alcohol use , schizophrenia and risk-taking . Mendelian r and omization analysis showed evidence for a causal positive influence of schizophrenia risk on cannabis use . Overall , our study provides new insights into the etiology of cannabis use and its relation with mental health . A GWAS of lifetime cannabis use reveals new risk loci , shows that cannabis use has genetic overlap with smoking and alcohol use , and indicates that the likelihood of initiating cannabis use is causally influenced by schizophrenia Not all individuals who smoke cannabis report psychotic-like experiences . Given that risk factors for psychotic disorders are multifaceted , precipitating factors to psychotic-like experiences after cannabis are likely to be equally complex . Reduced neurocognitive performance is associated with both psychosis risk and cannabis use . Therefore , it is possible cognitive performance may differentiate those who report psychotic-like experiences after cannabis from those who do not . We determined whether those reporting psychotic/dysphoric experiences after cannabis had reduced neurocognitive performance compared to those reporting primarily euphoric experiences . METHODS Participants were recruited on the basis of responses to the cannabis high captured by the Psychosis-Dysphoric and Euphoric experiences subscales from the Cannabis Experiences Question naire ( CEQ ) . RESULTS Compared to participants reporting primarily euphoric cannabis experiences ( n = 36 ; 44 % male ; mean age ( SD ) = 28 ( 9 ) years ) , those who reported psychotic/dysphoric experiences ( n = 40 ; 45 % male ; mean age ( SD ) = 26 ( 5 ) years ) demonstrated significantly faster responses to a trial and error learning task . In the presence of distracters , those with psychotic/dysphoric experiences after cannabis made more errors on a Continuous Performance Task . CONCLUSIONS Those who report psychotic/dysphoric experiences after cannabis have subtle inefficiencies in their cognitive processes . The multiple factors which predict vulnerability to psychotic-like experiences after cannabis require further investigation BACKGROUND Cannabis use is high amongst young people who have recently had their first episode of psychosis , and is associated with worse outcomes . To date , interventions to reduce cannabis consumption have been largely ineffective , and it has been suggested that longer treatment periods are required . METHOD In a pragmatic single-blind r and omized controlled trial 110 participants were r and omly allocated to one of three conditions : a brief motivational interviewing and cognitive behavioural therapy ( MI-CBT ) intervention ( up to 12 sessions over 4.5 months ) with st and ard care from an early intervention service ; a long MI-CBT intervention ( up to 24 sessions over 9 months ) with st and ard care ; or st and ard care alone . The primary outcome was change in cannabis use as measured by Timeline Followback . RESULTS Neither the extended nor the brief interventions conferred benefit over st and ard care in terms of reductions in frequency or amount of cannabis use . Also the interventions did not result in improvements in the assessed clinical outcomes , including symptoms , functioning , hospital admissions or relapse . CONCLUSIONS Integrated MI and CBT for people with cannabis use and recent-onset psychosis does not reduce cannabis use or improve clinical outcomes . These findings are consistent with those in the published literature , and additionally demonstrate that offering a more extended intervention does not confer any advantage . Many participants were not at an action stage for change and for those not ready to reduce or quit cannabis , targeting associated problems rather than the cannabis use per se may be the best current strategy for mental health services to adopt OBJECTIVE Cannabis use has been found to increase the risk of psychosis .  It is unclear whether , after a first psychotic episode has occurred , continued cannabis use is associated with poor functional outcome of psychosis . METHOD As part of a r and omized , open-label , controlled trial , the association of cannabis use and measures for psychopathology and social role functioning after 2 years of follow-up and for the recently proposed outcome measures of symptomatic remission , functional remission , and clinical recovery was explored in a group of 124 patients suffering from nonaffective first-episode psychosis ( diagnosed according to DSM-IV and included from a catchment area in the Netherl and s of 3.1 million inhabitants from October 2001 through December 2002 ) . Other patient characteristics that were expected to be independently associated with outcome , among them alcohol and other drug use , were assessed at baseline . RESULTS Continued cannabis use was not associated with symptomatic or functional remission or clinical recovery . After 2 years , cannabis use was related to certain aspects of social role functioning ( economic and social activities ; explained variance 5.6 % and 8.4 % , respectively ) but not to psychopathology ( Positive and Negative Syndrome Scale Positive , Negative , or General symptoms ) . CONCLUSIONS Our findings support the notion that continued cannabis use after the onset of a first-episode psychosis is correlated with worse social outcome and should be discouraged whenever possible , but its role in outcome is modest in comparison to other factors . TRIAL REGISTRATION Nederl and s Trial Register : http://www.trialregister.nl ( ID : NTR 374 ) Background : Cannabis use has a negative impact on psychosis . Studies are needed to explore the efficacy of psychological interventions to reduce cannabis use in psychosis . Our aim is to study the efficacy of a specific motivational intervention on young cannabis users suffering from psychosis . Methods : Participants ( aged less than 35 years ) were r and omly assigned to treatment as usual ( TAU ) alone , or treatment as usual plus motivational intervention ( MI + TAU ) . TAU was comprehensive and included case management , early intervention and mobile team when needed . Assessment s were completed at baseline and at 3 , 6 and 12 months follow-up . Results : Sixty-two participants ( 32 TAU and 30 MI + TAU ) were included in the study .  Cannabis use decreased in both groups at follow-up . Participants who received MI in addition to TAU displayed both a greater reduction in number of joints smoked per week and greater confidence to change cannabis use at 3 and 6 months follow-up , but differences between groups were nonsignificant at 12 months . Conclusions : MI is well accepted by patients suffering from psychosis and has a short-term impact on cannabis use when added to st and ard care . However , the differential effect was not maintained at 1-year follow-up . MI appears to be a useful active component to reduce cannabis use which should be integrated in routine clinical practice Drug users have attentional biases for drug-related stimuli , and the frequency of drug use and craving are associated with attentional bias . However , research to date has not investigated the relationship between the severity of cannabis dependence , and attentional bias for cannabis-related stimuli . In the present study , 28 recreational cannabis users completed a modified Stroop task with cannabis-related and control words , plus question naire measures of cannabis dependence and craving . Participants were split into those who met diagnostic criteria for cannabis dependence based on scores on the Cannabis Severity of Dependence Scale ( C-SDS ) , and those who did not . The cannabis-dependent group had a significant attentional bias for the cannabis-related words , but the non-dependent group did not . Correlations indicated that attentional bias was also associated with the frequency of cannabis use , and with subjective craving Medicinal cannabis has already entered mainstream medicine in some countries . This systematic review ( SR ) aim ed at evaluating the efficacy , acceptability and safety of cannabis-based medicines for chronic pain management . Qualitative systematic review of SRs of r and omized controlled trials with cannabis-based medicines for chronic pain management . The Cochrane data bases of SRs , Data base of Abstract s of Review s of Effects and PubMed were search ed for SR published in the period January 2009 to January 2017 . Assessment of the method ological quality of SR was performed by the AMSTAR checklist . Out of 748 papers identified , 10 SRs met the inclusion criteria . The method ological quality was high in four and moderate in six SRs . There were inconsistent findings of four SRs on the efficacy of cannabis-based medicines in neuropathic pain and of one SR for painful spasms in multiple sclerosis . There were consistent results that there was insufficient evidence of any cannabis-based medicine for pain management in patients with rheumatic diseases ( three SRs ) and in cancer pain ( two SRs ) . Cannabis-based medicines undoubtedly enrich the possibilities of drug treatment of chronic pain conditions . It remains the responsibility of the health care community to continue to pursue rigorous study of cannabis-based medicines to provide evidence that meets the st and ard of 21st century clinical care . SIGNIFICANCE We provide an overview of systematic review s on the efficacy , tolerability and safety of cannabis-based medicines for chronic pain management . There are inconsistent findings of the efficacy of cannabinoids in neuropathic pain and painful spasms in multiple sclerosis . There are inconsistent results on tolerability and safety of cannabis-based medicines for any chronic pain Objective To determine whether use of cannabis in adolescence increases the risk for psychotic outcomes by affecting the incidence and persistence of sub clinical expression of psychosis in the general population ( that is , expression of psychosis below the level required for a clinical diagnosis ) . Design Analysis of data from a prospect i ve population based cohort study in Germany ( early developmental stages of psychopathology study ) . Setting Population based cohort study in Germany . Participants 1923 individuals from the general population , aged 14 - 24 at baseline . Main outcome measure Incidence and persistence of subthreshold psychotic symptoms after use of cannabis in adolescence .  Cannabis use and psychotic symptoms were assessed at three time points ( baseline , T2 ( 3.5 years ) , T3 ( 8.4 years ) ) over a 10 year follow-up period with the Munich version of the composite international diagnostic interview ( M-CIDI ) . Results In individuals who had no reported lifetime psychotic symptoms and no reported lifetime cannabis use at baseline , incident cannabis use over the period from baseline to T2 increased the risk of later incident psychotic symptoms over the period from T2 to T3 ( adjusted odds ratio 1.9 , 95 % confidence interval 1.1 to 3.1 ; P=0.021 ) . Furthermore , continued use of cannabis increased the risk of persistent psychotic symptoms over the period from T2 to T3 ( 2.2 , 1.2 to 4.2 ; P=0.016 ) . The incidence rate of psychotic symptoms over the period from baseline to T2 was 31 % ( 152 ) in exposed individuals versus 20 % ( 284 ) in non-exposed individuals ; over the period from T2 to T3 these rates were 14 % ( 108 ) and 8 % ( 49 ) , respectively . Conclusion Cannabis use is a risk factor for the development of incident psychotic symptoms . Continued cannabis use might increase the risk for psychotic disorder by impacting on the persistence of symptoms The present investigation examined the relationships between motives for cannabis use and negative consequences associated with cannabis use following a brief intervention . The sample consisted of 205 adolescent cannabis users ( 66.3 % male ) , who were recruited in high schools and r and omly assigned to a brief two-session motivational enhancement therapy ( MET ) or an educational feedback control ( EFC ) . Results supported the hypothesis that using cannabis to cope with negative affect would predict the number of problems and dependence symptoms related to cannabis use , after controlling for age , gender , years and frequency of cannabis use , and internalizing and externalizing behavior problems . Significant interactions between internalizing behavior problems and the coping motive showed that using to cope was associated with a higher number of cannabis dependence symptoms among adolescents reporting lower levels internalizing behavior problems . Findings support the potential utility of conducting further research to explore the coping motive as an important indicator of problematic cannabis use Cognitive impairment and cannabis use are common among patients with schizophrenia . However , the moderating role of cannabis on cognition remains unclear . We sought to examine cognitive performance as a function of cannabis use patterns in schizophrenia . A secondary aim was to determine the effects of cumulative cannabis exposure on cognition . Cognition was assessed in male out patients with current cannabis dependence ( n=18 ) and no current cannabis use disorders ( n=29 ) . We then parsed non-current users into patients with lifetime cannabis dependence ( n=21 ) and no lifetime cannabis dependence ( n=8 ) . Finally , as an exploratory analysis , we examined relationships between cumulative cannabis exposure and cognition in lifetime dependent patients . Cross-sectional comparisons suggest that lifetime cannabis users demonstrate better processing speed than patients with no lifetime dependence . Exploratory analyses indicated that patients with current dependence exhibited robust negative relationships between cumulative cannabis exposure and cognition ; these associations were absent in former users . Cannabis status has minimal effects on cognition in males with schizophrenia . However , cumulative cannabis exposure significantly impairs cognition in current , but not former users , suggesting that the state dependent negative effects of cannabis may be reversed with sustained abstinence . Prospect i ve studies are needed to confirm these findings The relationships between executive processes , associative learning and different aspects of real world memory functioning were explored in a sample of cannabis users and nonusers . Measures of executive component processes , associative learning , everyday memory , prospect i ve memory , and cognitive failures were administered . Relative to nonusers , cannabis users were found to be impaired in several aspects of real world memory functioning . No other group differences were apparent . The absence of cannabis related deficits in those executive component processes and aspects of learning that are believed to support real world memory processes is surprising given that cannabis related deficits were obtained in real world memory . The present results are discussed within the context of neuroimaging evidence which suggests that cannabis users may exhibit different patterns of neural activation when performing executive tasks while not always exhibiting deficits on these tasks BACKGROUND Cannabis use is a major problem in inner cities and has been causally implicated in psychosis . Very few of the available hospital-based studies of the implication s of cannabis usage have involved psychiatric intensive care units ( PICU ) ; but PICU receive many of the most challenging and re source -hungry- and incompletely understood- patients in the mental health system . AIMS To study the clinical impact of cannabis abuse in a PICU , and to compare the use of atypical and typical antipsychotics in this setting . METHOD 115 patients admitted to a PICU consented to take part in an open label naturalistic study .  BPRS , TCI-240 , weight , length of admission and routine bloods were evaluated in all participants . RESULTS There was a high rate of cannabis abuse ( 71.3 % ) in the PICU population . Patients who abused cannabis spent longer in PICU because their psychoses were more severe . They were younger at first hospital admission . Cannabis also had metabolic implication s , with higher blood glucose levels at admission and greater weight increase .  Atypical antipsychotics were effective in treating psychosis in patients positive to cannabis at admission . CONCLUSION Our findings suggest that cannabis abusers had a more severe psychotic illness , especially in schizophrenia . There are additional complications in terms of weight gain for cannabis users While the effects of cannabis use on retrospective memory have been extensively examined , only a limited number of studies have focused on the links between cannabis use and prospect i ve memory . We conducted two studies to examine the links between cannabis use and both time-based and event-based prospect i ve memory as well as potential mechanisms underlying these links . For the first study , 805 students completed an online survey design ed to assess cannabis consumption , problems with cannabis use indicative of a disorder , and frequency of experiencing prospect i ve memory failures . The results showed small to moderate sized correlations between cannabis consumption , problems with cannabis use , and prospect i ve memory . However , a series of mediation analyses revealed that correlations between problems with cannabis use and prospect i ve memory were driven by self-reported problems with retrospective memory . For the second study , 48 non-users ( who had never used cannabis ) , 48 experimenters ( who had used cannabis five or fewer times in their lives ) , and 48 chronic users ( who had used cannabis at least three times a week for one year ) were administered three objective prospect i ve memory tests and three self-report measures of prospect i ve memory . The results revealed no objective deficits in prospect i ve memory associated with chronic cannabis use . In contrast , chronic cannabis users reported experiencing more internally-cued prospect i ve memory failures . Subsequent analyses revealed that this effect was driven by self-reported problems with retrospective memory as well as by use of alcohol and other drugs . Although our sample s were not fully characterized with respect to variables such as neurological disorders and family history of substance use disorders , leaving open the possibility that these variables may play a role in the detected relationships , the present findings indicate that cannabis use has a modest effect on self-reported problems with prospect i ve memory , with a primary problem with retrospective memory appearing to underlie this relationship BACKGROUND Evidence regarding the association between cannabis use and depression  remain conflicting , especially as studies have not typically adopted a longitudinal design with a follow-up period that was long enough to adequately cover the risk period for onset of depression . METHOD Males from the Cambridge Study in Delinquent Development ( CSDD ) ( N = 285 ) were assessed seven times from age 8 to 48 years to prospect ively investigate the association between  cannabis use and risk of  major depressive disorder ( MDD ) .  A combination of multiple analyses ( logistic regression , Cox regression , fixed-effects analysis ) was employed to explore the strength and direction of effect within different developmental stages . RESULTS Multiple regression analyses revealed that early-onset cannabis use ( before age 18 ) but not late-onset cannabis use ( after age 27 ) was associated with a higher risk and shorter time until a subsequent MDD diagnosis . This effect was present in high-frequency [ ( odds ratio ( OR ) 8.83 , 95 % confidence interval ( CI ) 1.29 - 70.79 ] ; [ hazard ratio ( HR ) 8.69 , 95 % CI 2.07 - 36.52 ) ] and low-frequency early-onset users ( OR 2.41 , 95 % CI 1.22 - 4.76 ; HR 2.09 , 95 % CI 1.16 - 3.74 ) . Effect of increased frequency of cannabis use on increased risk of subsequent MDD was observed only for use during adolescence ( age 14 - 18 ) but not at later life stages , while controlling for observed and non-unobserved time-invariant factors . Conversely , MDD in adulthood ( age 18 - 32 ) was linked to a reduction in subsequent cannabis use ( age 32 - 48 ) . CONCLUSIONS The present findings provide evidence implicating frequent cannabis use during adolescence as a risk factor for later life depression . Future studies should further examine causality of effects in larger sample
The results show that , in particular , frequent cannabis use , especially daily use , and the consumption of high-potency cannabis are associated with a higher risk of developing psychosis .
Moreover , several genotypes moderate the impact of cannabis use on psychosis risk , particularly those involved in the dopamine function , such as AKT1 .
Finally , cannabis use is associated with an earlier psychosis onset and increased risk of transition in individuals at a clinical high risk of psychosis .
These findings indicate that changing cannabis use behavior could be a harm reduction strategy employed to lower the risk of developing psychosis .
Increasing evidence indicates a relationship between  cannabis use and psychosis risk .
Specific factors , such as determinants of cannabis use or the genetic profile of cannabis users , appear to moderate this association .
The present systematic review presents a detailed and up-to- date literature overview on factors that influence the relationship between cannabis use and psychosis risk .