Select Committee on Science and Technology Written Evidence


Memorandum from Rethink


  Cannabis is the most widely used illegal drug in the UK. There is a now a substantial body of scientific research indicates a positive relationship between cannabis use in adolescence and the later onset of psychosis; other research establishes a positive relationship between cannabis use and relapse by people with psychotic illnesses; a small amount of research has now been undertaken on the relationship between cannabis use and wider mental health problems.

  The UK Government has not contributed to the expansion of this evidence base, either through commissioning evidence or through funding applications submitted to it. It took a significant decision to reclassify cannabis to a class C drug in 2004, but did not use the subsequent information campaign to communicate the evidence. A project to provide information materials to people with mental illness was vastly under-funded and flawed. School drugs education has not covered this evidence either. The body charged with reviewing evidence by the Government, the Advisory Council on the Misuse of Drugs, was only asked to review this evidence following media pressure.

  This poor record has been followed in January 2006 by a decision to keep cannabis at class C, invest further in health education and review evidence on the recommendation of ACMD and the majority of mental health and drug charities.

  Rethink believes that the failures of Government policy to reflect the evidence base has been due to a number of factors, including the politicisation of the issue, the cross-cutting nature of the issue, a reliance on single experts in departments and professionals rather than people with mental illness and their carers to direct policy.

  Hence, we make the following recommendations.

Recommendation 1:

  Guidance to civil servants and Ministers stress the importance of considering and commissioning evidence on all aspects of cross-cutting issues.

Recommendation 2:

  Guidance to civil servants should stress the importance of consulting a variety of resident experts and practicing professionals.

Recommendation 3:

  A mechanism be created through which service users, carers and organisations representing these groups can inform Departmental decisions on research funding, commissioning and determining future priorities.

Recommendation 4:

  Users of drug and mental health services, their carers and organisations representing these groups to be included in the make-up of committees such as ACMD.

Recommendation 5:

  Guidance to civil servants to stress the need to consult service users and carers as well as professionals, at all stages of the policy-making process.

Recommendation 6:

  A mechanism be created through which service users, carers and organisations representing these groups can inform Departmental decisions on research funding, commissioning and determining future priorities.

Recommendation 7:

  The advice given by Government-appointed bodies such as ACMD and Government policy to be regularly evaluated by external organisations.


  Rethink is a national charity, with over 8,000 members comprising both people with severe mental illness and their carers. Rethink operates almost 400 services for people with severe mental illness across England and Northern Ireland.

  Rethink has campaigned on the issue of cannabis for many years because our members have consistently identified it as a major issue and because of emerging scientific evidence linking cannabis and mental illness.

  Cannabis is the most widely used illegal drug in the UK—rates of use among young people are said to be falling a small amount (Health and Social Care Information Centre, 2005), but are still the highest in Europe (European Monitoring Centre for Drugs and Drug Addiction, 2002).


 (1)   Cannabis use and the onset of psychosis

(a)  epidemiology

(i)  association

  A clear association between use of cannabis and psychosis has been established by several longitudinal population cohort studies. The US National Epidemiological Catchment Area Study examined 20,000 community and institutional residents in the early 1980s. Using this sample and matching cases and controls for social and demographic characteristics, Tien and Anthony (1990) reported that people who used cannabis on a daily basis were 2.4 times more likely to report psychotic experiences than non-daily cannabis users (after adjusting for alcohol use and psychiatric diagnoses). Similarly, the Australian National Survey of Mental Health and Well-being 1997 (Hall et al, 1998) found that those who met the International Classification of Disease (ICD)-10 criteria for cannabis dependence were nearly three times more likely to report that they had been diagnosed with schizophrenia than those without cannabis dependence disorder.

  These studies do not, however indicate the direction of the association between cannabis and psychosis, suggesting two possible hypotheses:

      1.    "Temporal priority hypothesis"—Cannabis use precedes development of psychosis.

      2.    "Self-medication hypothesis"—Cannabis use is a consequence of psychosis with people using it to self-medicate their symptoms.

(ii)  temporal priority

  Other population studies provide evidence for cannabis use preceding the development of psychotic symptoms. The Swedish Conscript Cohort (Andréasson et al, 1987) followed up 50,087 Swedish conscripts and found evidence for a "dose-dependent" relationship between cannabis use at 18 years and diagnosis of schizophrenia 15 years later. Heavy users of cannabis, with no psychiatric diagnosis at conscription, were 2.3 times more likely to be diagnosed with schizophrenia later in life (after adjustment for confounding variables). The authors noted, however, that only 3% of heavy cannabis users went on to develop schizophrenia suggesting that it may only affect those who have some other pre-existing vulnerability to psychosis.

  One of the limitations of this study is the large temporal gap between cannabis use at 18 years and onset of schizophrenia 15 years later, with no assessment of cannabis use or other drug use in the intervening period.

  The sample was also followed up by Zammit et al (2002) across the period 1970 to 1996. They found that the risk of developing schizophrenia was increased (odds ratio = 1.9) in those who had ever reported cannabis use at baseline. A dose-dependent effect was again found, with those who had used cannabis more than 50 times prior to assessment having a further increased risk of developing schizophrenia (odds ratio = 6.7).

  This study used a more complete psychiatric register and controlled better for confounding variables such as other drug use, known risk factors for schizophrenia, IQ and social integration, but still found a relationship between cannabis use and schizophrenia. The authors estimated that 13% of schizophrenia could be averted if all cannabis use were prevented.

  The Netherlands Mental Health and Incidence Study (Van Os et al, 2002) examined the relationship between cannabis use and psychosis amongst the general population (n=4,045) and subjects with self-reported symptoms of psychosis (n=59). They found that users of cannabis at baseline were nearly three times more likely to show psychotic symptoms at follow-up three years later. This risk remained significant even after a variety of confounding factors were controlled for. They also found evidence for a "dose-dependent" relationship with the heaviest users showing the highest risk. The authors estimated the attributable risk of cannabis to psychosis to be 13%, similar to Zammit's earlier finding. The relationship between cannabis use and psychotic symptoms was found to be even stronger for people with more severe psychotic symptoms who required care. The attributable risk of cannabis to severe psychotic symptoms was estimated at 50%. This study is limited, however, by the short follow up period.

  The Dunedin Multidisciplinary Health and Development Study examined a general population birth-cohort of 1,037 subjects born in Dunedin in 1972-73 with follow up at age 26. The key advantage of this study is that the authors collected data on self-reported psychotic symptoms at age of 11, before the onset of cannabis use. They found that individuals reporting cannabis use at ages 15 and 18 had higher rates of psychotic symptoms at age 26 when compared to non-users. This association remained significant after controlling for psychotic symptoms before the onset of cannabis use (Arseneault et al, 2002). A significant effect of age was also found, with cannabis use at 15 resulting in an increased likelihood of meeting diagnostic criteria for schizophreniform disorder at 26. Further, 10.3% of age 15 cannabis users were diagnosed with schizophreniform disorder at age 26 compared to 3% of controls. This suggests a strong developmental effect of early cannabis use.

  In addition to establishing temporal priority, the Dunedin Study also found evidence for specificity of outcome, as cannabis use at age 15 did not predict depressive symptoms at age 26, and specificity of exposure, as the use of other illicit drugs did not predict schizophrenia outcomes over and above cannabis use. The authors concluded that "using cannabis in adolescence increases the likelihood of experiencing symptoms of schizophrenia in adulthood".

  A significant effect of age was replicated in a recent study by Stefanis et al (2004), which examined 3,500 subjects who formed part of the Greek Birth Cohort Study. Participants were administered a postal questionnaire which examined drug use and psychotic symptoms at age 19. Cannabis life-time frequency use was associated positively with positive psychotic symptoms. This effect size was much larger for those who had started cannabis use earlier in adolescence (pre-15 years). This evidence is limited as it is cross-sectional only, although the significant effect of age suggests that cannabis use preceded the development of psychotic symptoms.

  A second general population birth-cohort study, the Christchurch Health and Development Study, was conducted in New Zealand, which followed up 1,265 children at ages 18 and 21. As part of the study, data was collected on cannabis use and psychotic symptoms. They found that young people meeting DSM-IV criteria for cannabis dependence had elevated rates of psychotic symptoms at both age 18 (rate ratio = 3.7) and age 21 (rate ratio = 2.3) after adjusting for many variables, including self-reported psychotic symptoms, other drug use and other psychiatric disorders. The authors concluded that this showed that the development of cannabis dependence is associated with increased rates of psychotic symptoms.

  More recently, Ferdinand et al (2005) conducted a longitudinal population based study with 2,076 young children and adolescents recruited in 1983 from the province of Zuid-Holland. Subjects were followed up in 1997, when they were between the ages of 18 and 30. They found that cannabis use was a risk factor for psychotic symptoms in initially psychosis-free individuals and that this risk was increased almost three-fold when compared to non-users. They also found some support for the self-medication hypothesis, with psychotic symptoms predicting future cannabis use. The hazard ratio for cannabis use preceding psychotic symptoms was higher than that for psychotic symptoms preceding cannabis use (2.81 versus 1.70).

  Thus several studies have suggested clear temporal priority for cannabis use. We do recognise some problems with these studies, including heterogeneity of outcome across studies, the use of self-report measures and limited statistical power. However, conclusively demonstrating the causal role of cannabis in the development of psychosis is necessarily difficult, given the practical difficulties of using animal models and ethical impossibility of human controlled trials. Adjusting epidemiological data for confounding risk factors for psychosis also presents enormous statistical difficulties. Given these constraints, we find the evidence for a relationship between early cannabis use and later psychotic symptoms compelling.

  We also believe that the level of evidence required should be set against the level of risk identified by these studies. The development of a psychotic disorder is a serious and significant experience in an individual's life. The studies presented above indicate that cannabis use significantly increases the risk of this outcome. It is in this context that we make our recommendations for policy. However, we would support further epidemiological research to confirm the results of these studies.

(iii)  other findings

  A variety of other epidemiological research weakens the self-medication hypothesis.

  A follow-up study in 1989 of the Swedish Conscript Cohort (Andreasson et al, 1989) found that cannabis users who developed schizophrenia had better premorbid personalities, a more abrupt onset of the condition and more positive symptoms than non-cannabis users who had schizophrenia. Earlier research also suggested that cannabis users who develop schizophrenia have better premorbid adjustment as well as having fewer negative symptoms and better treatment outcomes (Allebeck, 1991). More recently, a study over five years of Issac (1995) found that among inpatients in South London, with the exception of patients with diabetes, cannabis users tended to have more severe psychotic symptoms on admission.

  An innovative study (Verdoux, 2002) used self-reports of drug use and psychotic symptoms from 79 college students, taken at random times over seven days. A positive association was found between cannabis use and unusual perceptions and a negative association between cannabis use and hostility. There was no temporal relationship between reporting unusual experiences and cannabis use, as the self-medication hypothesis would predict.

  A number of studies have found that people with schizophrenia give similar reasons to other substance users for their use of cannabis and other drugs, eg to relax or socialise, to feel good, relieve boredom or provide stimulation. (Dixon et al, 1990; Bergman et al 1985; Noordsky et al, 1991; Test et al, 1989).

  Two reviews of the evidence concluded respectively that: "on the basis of the best evidence currently available, that cannabis use is likely to play a causal role with regard to schizophrenia" (Arsenault et al, 2004) and "cannabis is an independent risk factor both for psychosis and development of psychotic symptoms" (Semple et al, 2005).

(iv)  outstanding issues

  If cannabis were a risk factor for schizophrenia, one would expect that rates of schizophrenia would increase as cannabis use increases. In Britain, cannabis use amongst young people appears to have increased substantially over the past 30 years, from around 10% reporting lifetime use in 1969-70 to 50% reporting lifetime use in 2001.

  Initial data on the incidence of schizophrenia suggests that it has not increased, but instead stabilised or slightly decreased over the relevant time period. However, there are a number of factors which may account for this data, in particular changes in service design and a narrowing of the diagnostic criteria for schizophrenia. Hence Kendell (1993) concluded that despite reports of a falling incidence for schizophrenia in the UK, it would be rash to conclude that rates of schizophrenia were falling (Kendell, 1993). In some specific geographical areas, it seems that the incidence of schizophrenia has increased significantly. Boydell (2003) concluded that the incidence of schizophrenia had doubled in thirty years in Camberwell, South East London (Boydell, 2003). This study included all psychiatric contracts, rather than just admissions, and thus minimised the effects of changes in service provision. It also identified all possible cases of psychosis in the first instance, to minimise the effect of diagnostic delay or administrative inaccuracy.

  Given the difficulties in establishing changes in the incidence of schizophrenia, we do not believe that the current evidence on incidence refutes the significant amount of epidemiological evidence pointing to a relationship between both adolescent cannabis use and heavy cannabis use and later psychotic symptoms.

 (b)  Neuroscience

  Neuroscientific research gives evidence of mechanism by which cannabis use may give rise to psychotic symptoms.

  Two cannabinoid receptors have been identified: CB1 and CB2 (Institute of Medicine, 1999; Pertwee, 2002), though others may exist (Wiley and Martin, 2002). The CB1 receptor is responsible for the psychological effects of THC (Heustis et al, 2001), whereas the role of CB2 is less clear.

  The CB1 receptor is most heavily concentrated in the mesolimbic and mesocortical pathways, both believed to be important for the development of schizophrenia (Ameri, 1999). Interaction between CB1 and dopamine D2 receptors has been documented in rats and monkeys (Meschler et al, 2001). Cannabis increases dopaminergic activity in the mesolimbic system (Ameri, 1999).

  This research gives some biological plausibility to the temporal priority hypothesis discussed above.

 (c)  Conclusion

  Epidemiological evidence, underpinned by neuroscientific research, suggests that there is a relationship between both adolescent cannabis use and heavy cannabis use and the onset of psychosis. However, many questions remain and require further study. We do not believe that the current evidence on incidence convincingly refutes the temporal priority hypothesis.

(2)   Other mental health problems

  Some epidemiological studies have also established an association between cannabis use and poor mental health more generally.

  A cross-sectional study has found an association between cannabis use and low life-satisfaction, contact with mental health services and hospitalisation (Kandel, 1984). Fergusson, Horwood and Swain-Campbell (2002) found relationship between cannabis use and suicidal behaviour after adjusting for confounding variables, which was both dose-responsive and stronger the earlier the onset of cannabis use. Rey et al (2002) found that in a nationally representative sample of adolescent Australians, cannabis users were three times more likely than non-cannabis users to experience depression. Fergusson et al (1997) found evidence for a relationship between cannabis use and major depression among the Christchurch birth cohort, with heavy users (defined as having used 10+ times) twice as likely as non-heavy users (having used one to nine times) and three times more likely than non-users to meet criteria for mood disorders. The Zurich cohort study found that those meeting criteria for depression by age 30 were 2.3 times more likely than the general population to use cannabis regularly (Angst, 1996). Another study found that 68% of female cannabis users were depressed (Patton et al, 2002).

  However, other studies have not found a relationship between adolescent and depression or found that it is insignificant after adjusting for confounding variables (Fergusson and Horwood, 1997; Brook, Cohen and Brook, 1998; McGee et al, 2000).

  Some studies have also found evidence for a link between cannabis use and suicide among adolescents, which remains after adjusting for confounding variables (Borges et al, 2000; Beautrais et al, 1999, Andreasson and Allebeck, 1990). Other studies have found an association but not a relationship which remains after adjustment (Fergusson and Horwood, 1997; Patton et al, 1997).

  In both these areas, there is a need for more research and better designed studies to clarify the relationship between cannabis use in adolescence and suicide and depression/affective disorders.

(3)   Relapse

  The negative effects of cannabis use on people with psychotic illness have been well-established, initially through case studies. In a retrospective study of people with schizophrenia, Negrete et al (1986) found higher rates of continuous hallucinations and delusions, and more hospitalisations amongst active users. Jablensky et al (1992) replicated these findings in a two-year follow up study of 1,202 patients with first-episode schizophrenia enrolled in 10 countries as part of a World Health Organisation (WHO) Collaborative Study. Linszen et al (1994) conducted the first large prospective cohort study, comparing 24 users with 69 non-users over a year with assessments of mental state on a monthly basis. Cannabis users experienced significantly more, and earlier, psychotic relapses or exacerbation of symptoms over the 12 month period and the effect was dose-responsive. Martinez-Arevalo et al (1994) followed up 62 young adults with schizophrenia over a one year period and found that cannabis use was the best predictor of relapse and hospitalisation during this time.

  In a longer term prospective study, Caspari (1999) followed up 39 patients with schizophrenia over 68 months and found a significantly higher rate of rehospitalisation. Cannabis users also tended to have poorer psychosocial functioning than non-users and higher scores on the "thought disturbance" and "hostility" items of the Brief Psychiatric Rating Scale (BPRS), though the strength of these findings is weakened by the fact that only one assessment of mental state was made once at the end of the 68 months.

  More recently, Issac et al (2005) studied 115 patients admitted to a psychiatric intensive care unit in South London, assessing mental state using the BPRS every two weeks during their admission period. People with a history of cannabis abuse were found to be younger on first admission and had more previous hospital admissions. Urinanalysis indicated that 25% of the sample used cannabis during admission, and those that did use during admission tended to spend longer in hospital.

  There is clear evidence to support the hypothesis that the use of cannabis by patients with a diagnosis of schizophrenia does result in an exaceberation of psychotic symptoms. This mitigates against the self-medication hypothesis with patients using cannabis to alleviate their symptoms.


 (a)  Government policy on cannabis

  In October 2001, the Home Secretary asked the Advisory Council no the Misuse of Drugs to review the classification of cannabis. In March 2002, the Advisory Council reported and concluded that:

        "no clear causal link has been demonstrated. The onset of schizophrenia often occurs in the late teens, when cannabis use is most common, so that an association is inevitable."

  The report goes on to recommend that cannabis be reclassified from class B to C, on the basis that the harm associated with it was less than other class B drugs. It was subsequently reclassified in January 2004.

  At the time this report was written, only the Andreasson (87) study had been made public, so there was not a large evidence base from which to make this judgement. However, by the time that cannabis was in actually reclassified to class C, in January 2003, a number of other studies had been published, including Zammit (02), Van Os (02), Arsenault (02). In the light of this, we find it surprising that a further review of the evidence was not ordered before the reclassification decision was implemented.

  In January 2005, following an extensive media campaign by Rethink on the anniversary of reclassification, the Department of Health announced a review of epidemiological evidence on cannabis and the aetiology of mental illness. In March 2005, the Home Secretary asked ACMD to look again at evidence on cannabis and reconsider its classification.

  In January 2006, ACMD's report was released, which recommended that cannabis remain a class C drug, that a sustained public education and information strategy about the hazards of cannabis be created, that services for individuals with cannabis problems be reviewed, measures to protect people with schizophrenia on in-patient wards be strengthened and a research programme on cannabis and mental health be instituted.

 (b)  Government's role in increasing the evidence base

  The Government has singularly failed to commission looking at the impact of cannabis on mental health. No major study so far on this issue has hence originated from the UK. This seems a significant failure on the part of the Government, given that hints of an important impact on mental health date back to 1987, as noted above. ACMD in 2001 too failed to recommend more research on the issue, even though it noted that the debate on it was long-running.

  Applications to the Department of Health for funding for studies on this question have also been consistently rejected, even though some were strong, in Rethink's view.

  Government has also failed to commission studies looking at the impact of legal penalties or classification on the use of cannabis. There is very little knowledge globally on how the relative effectiveness of legal status, drugs education and information campaigns on reducing usage levels.

 (c)  Communication of evidence

(i) To the general public

  To our knowledge, the British Government has never attempted to communicate the mental health risks of cannabis use to the wider public. Indeed, opportunities to do so have been missed.

  For example, when cannabis was reclassified to Class C in the UK January 2004, the public health campaign that accompanied reclassification did not mention the possible mental health effects of cannabis, but instead concentrated solely on the physical health effects of use and its continued illegality.

  This contrasts with the action of the French Government, which in 2005 invested €3.8 million in the communications side of its cannabis campaign. This is particularly noteworthy, given that the latest evidence suggests that France has a lower level of cannabis use among young people than the UK. In France, 35.7% of young adults report lifetime use (compared with 40.4% in the UK) and 4.9% of young adults report use in the last year (compared with 16.6% in the UK) (European Monitoring Centre for Drugs and Drug Addiction, 2002).

(ii) To school-age children

  Opportunities within school drugs education have also been missed. Current DfES drugs guidance stresses the physical health effects of cannabis, the possibility of dependence and especially its illegality, but dismisses the evidence on mental health effects:

        ". . . there has been a lot of debate about whether the use of cannabis can lead to mental illness, especially schizophrenia. However, no clear causal link has been proven for the latter, although cannabis can worsen existing schizophrenia and other mental illnesses and lead to relapse in some people.

        It is important for schools to reinforce to pupils the message that cannabis is harmful to health and is still an illegal drug, and that possession remains a criminal offence leading to a possible criminal conviction" (DfES, 2004;25)(emphasis DfES)

  Cannabis education in schools has also been conducted too late. Research suggests that one factor determining the success of drugs education is ensuring that it is delivered at a relevant time in young people's development (McBride, 2005) and the current statistics on cannabis use among young people in the Britain. The latest statistics reveal that 1% of 11 year olds, 2% of 12 year olds, 7% of 13 year olds, 17% of 14 year olds and 26% of 15 year olds had used cannabis in the last year (Health and Social Care Information Centre, 2005). This would suggest that any intervention in British schools should take place before the age of 14, possibly before the age of 13, with booster sessions following this, in order to maximize effectiveness.

  Studies have also shown that school drugs education can delay the age of first use, can reduce the number of young people who go on to frequent or high use and reduce drugs-related harms (Maggs and Schulenberg, 1998; Dijkstra et al, 1999; McBride et al, 2004; DfES, 2004). Given that the major risks involved with cannabis are dependent on the age and quantity of use, drugs education in this area seems a particularly appropriate intervention.

  Furthermore, there is evidence of an inverse relationship between recall of drugs cannabis education and cannabis use. Among Year 11 pupils, those who did not remember having lessons about drugs in the last year were more likely than those who did to have used cannabis in the last month (21% compared with 16%). This contrasts with the evidence on recall of tobacco and alcohol-related lessons, where recall was found to have no impact on rates of either tobacco or alcohol use (Health and Social Care Information Centre, 2005), suggesting that education in relation to cannabis may be even more effective in deterring use among young people than tobacco or alcohol education.

 (iii)  To people with mental illness

  The 2001 ACMD report does note the potential risk of cannabis use to people with existing mental health problems. Its view on this was very clear:

        "Cannabis can unquestionably worsen schizophrenia (and other mental illnesses) and lead to relapse in some patients. Its use should therefore be particularly discouraged in all people with mental health problems."

  Despite this, there was no attempt until 2004 to create information materials for people with mental illness about the risks of cannabis. Even this attempt was flawed, as only £230,000 was allocated to the project. With approximately 1% of the population currently experiencing psychotic symptoms, this equates to a spend of less than one pence per head of the population experiencing psychosis and in touch with mental health services.

  As part of this project, research was commissioned from Cragg, Ross and Dawson (unpublished), to look at people's information needs and to make recommendations as to how the evidence on cannabis might be communicated. This researched highlighted an explanation used successfully by many psychiatrists in explaining the mental health risks of cannabis to their patients, especially those who were embedded in cannabis culture and hence could not believe that it was causing them harm when others seemed to be able to tolerate it well. The explanation used was that some people had a "cannabis allergy"—this was said to work very well as awareness of food allergies and intolerances was growing among the public. Despite this evidence from professionals of its usefulness, it was rejected by officials working on the materials after advice from the Department of Health. The grounds for rejecting it were that whilst people who had an allergy to a food experienced an adverse reaction to it very quickly, sometimes even instantaneously, those who experienced adverse mental health effects from cannabis often would not feel them until years later. Whilst there is some truth in this argument, there was no further work done to try and present this analogy in a way which would avoid this problem.

  Once draft materials had been produced, further research was done with people with mental illness, their carers and professionals to test out the materials. The feedback gained from most groups was negative and hence it was decided to rework the materials. In this case, the decision was well grounded in evidence.

  The project has now been put on hold, pending the advice of ACMD, despite the fact that the evidence on cannabis use by people with mental health problems was never in question.

  As well as specific communications campaigns, there is an opportunity for Government to use existing health awareness programmes to communicate messages on cannabis. However, so far, such programmes (eg the Expert Patient Programme) do not, in our view, cover the issue of cannabis sufficiently, if at all.


 (a)  Politicised debate

  Cannabis has been a politicised issue since the beginning of the twentieth century and "reefer madness". In this contested arena, it has been difficult for Departmental Advisors and experts of all kinds to look objectively at evidence. At a conference in September 2005 on cannabis, Griffith Edwards, the founder of the National Addiction Centre, pinpointed the two possible errors made in the cannabis policy arena: the positive error where too much credence is given to findings and the negative error, where findings are dismissed too easily. He concluded that 20 years ago, the positive error had been rife; now, it is the negative error that is rife. Hence the evidence has often not been looked at objectively. The ACMD report of 2005 is a notable exception to this trend.

 (b)  Role of the media

  Because of the politicisation of this issue, there has been a high level of media interest. This has meant that the Government has sometimes been under pressure to make rapid decisions to respond to criticism in the media. Hence, the announcement of the Department of Health's review of evidence in January 2005. However, in the case of the decision to refer the issue to ACMD, this has led to well evidenced policy-making.

  The media has, however, played an extremely important role in communicating evidence on cannabis and psychosis to the general public. Coverage of the issue has been significant and has made a valuable contribution to educating the public about this issue and in promoting discussion of it.

 (c)  Cross-over between departments

  The issue of cannabis and mental illness does not fit easily into Governmental or Departmental structures, lying between the Home Office and the Department of Health and between public health, mental health, and substance misuse. Hence, monitoring research on this issue does not seem to have been part of the core function of any one team—officials seem to have "dipped into" the issue at certain points, because they were asked for advice, but not followed the succession of findings on the matter closely. This "dipping in and out" has allowed people to look at individual pieces of evidence within the context of their pre-conceived ideas on the issue, rather than questioning their view of cannabis.

  Cannabis is part of both the law enforcement and health agendas. There has been no attempt to look at cannabis policy "in the round", to consider the interaction of public health education initiatives, information provision in mental health services, drug service provision and law enforcement. Officials and Ministers need to be encouraged to look at such cross-cutting issues in a more coherent and comprehensive manner.

Recommendation 1: Guidance to civil servants and Ministers stress the importance of considering and commissioning evidence on all aspects of cross-cutting issues.

 (d)  Reliance on a single experts in Government

  Despite this, we have experience of officials relying on only one expert, often an internal expert, to provide advice on cannabis. Often, officials do not then challenge this advice—it is regarded as an "expert view" and is seen as absolute, though in fact it may be partial.

  This seems to be particularly problematic if the "expert" in the Government department has a professional background linked to the issue—in this case, as a psychiatrist, mental health nurse or researcher. Often, people with a professional background are employed by Government departments and are seen as resident experts in that field by career civil servants, because of their experience "in the field". Whilst their advice can be valuable, it is too often seen by officials as absolute. Some of these experts are consulted on too wide a range of issues than they can reasonably be expected to have mastered, a far wider range than any official would be. The view of any one professional would be considered a useful, but partial view, if they were responding to a Government consultation—it does not seem right that a single official's view is prioritised purely because of their prior professional experience.

  Furthermore, it is questionable how far the views of these experts reflect current professional practice—the longer they work in Government, the more removed are their experiences from current practice and experience. Given that cannabis use has increased significantly in the past two decades, professionals' experience in mental health facilities has changed also—experts who are out of touch with current professional practice are likely to be out of touch with these experiences.

  Experts are also far more likely than practicing professionals to influence decisions on research funding and commissioning. Given that practicing professionals have more relevant experience, they should have a means in which to influence such decisions and recommend future priorities.

Recommendation 2: Guidance to civil servants should stress the importance of consulting a variety of resident experts and practicing professionals.

Recommendation 3: A mechanism be created through which service users, carers and organisations representing these groups can inform Departmental decisions on research funding, commissioning and determining future priorities

 (e)  Reliance on professionals, rather than service users

  To our knowledge, there is no-one with personal experience of using drug or mental health services involved in making cannabis policy. This seems a significant omission especially in the make-up of ACMD. Including people with mental illness and/or substance use problems on such bodies could help ensure that they are more in touch with current issues for people and that views are grounded in experience, rather than preconceived ideas. Organisations which represent service users could also play an important role. A similar case could be made for carers playing a role on such bodies.

  Service users also seem to be the last port of call for officials making cannabis policy—this was certainly our experience in the COI project to create information materials on cannabis. Given that these materials were destined for people with mental illness, it seemed foolish not to consult people with mental illness at an earlier stage about what kind of information they needed, as well as design and other issues. In the research on information needs, mentioned above, service users were not as well-represented as professionals.

  There is currently no mechanism for service users, carers and organisations representing them to make suggestions and recommendations for future research funding.

Recommendation 4: Users of drug and mental health services, their carers and organisations representing these groups to be included in the make-up of committees such as ACMD.

Recommendation 5: Guidance to civil servants to stress the need to consult service users and carers as well as professionals, at all stages of the policy-making process.

Recommendation 6: A mechanism be created through which service users, carers and organisations representing these groups can inform Departmental decisions on research funding, commissioning and determining future priorities.

 (f)  Lack of evaluation

  The policy making process on cannabis does not seem to be evaluated in a systematic or formal way. ACMD's advice, for example, has never been evaluated by an external body. We believe that these processes, like other Government processes, deserve to be reviewed by an external body.

Recommendation 7: The advice given by Government-appointed bodies such as ACMD and Government policy to be regularly evaluated by external organisations.

 (g)  Time lag

  As noted above, there was a significant time lag between the review of ACMD in 2001 and the implementation of reclassification in 2003. In this period, a significant amount of new evidence emerged about cannabis and mental illness, but the cannabis decision was not revisited in the light of this. This did not happen despite the efforts of Rethink to bring the new evidence to the attention of Government. There needs to be a mechanism for reviewing evidence and updating recommendations between the point where policy recommendations are made and they are implemented. Once a major policy decision (such as that to re-classify) has been taken, further research relating to that decision should be systematically monitored and reported to Ministers responsible.

Recommendation 8: Major policy decisions to be accompanied by a commitment to monitor research developments until and following implementation.

January 2006

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Prepared 31 July 2006