An Intervention for Substance Abuse in Schizophrenia

Cannabis use and the risk of developing a psychotic disorder

WE BRIEFLY REVIEW THE EVIDENCE THAT CANNABIS USE IN ADOLESCENCE AND YOUNG ADULTHOOD IS A CONTRIBUTORY CAUSE OF SCHIZOPHRENIFORM PSYCHOSES, BY SUMMARISING LONGITUDINAL STUDIES THAT: a) have examined relationships between cannabis use and the risk of psychosis or psychotic symptoms; and b) have controlled for potential confounders, such as other forms of drug use and personal characteristics that predict an increased risk of psychosis. There is now reasonable evidence from longitudinal studies that regular cannabis use predicts an increased risk of schizophrenia and of reporting psychotic symptoms. These relationships have persisted after controlling for confounding variables such as personal characteristics and other drug use. The relationships did not seem to be explained by cannabis being used to self-medicate symptoms of psychosis. A contributory causal relationship is biologically plausible because psychotic disorders involve disturbances in the dopamine neurotransmitter system with which the cannabinoid system interacts, as has been shown by animal studies and a human provocation study. We briefly explore the clinical and public health implications of the most plausible hypothesis, that cannabis use precipitates schizophrenia in persons who are vulnerable because of a personal or family history of schizophrenia.

What are the policy implications of the evidence on cannabis and psychosis?

OBJECTIVE

To explore the implications for mental health services, for health education about the risks of cannabis use, and for public policy toward cannabis use of observational evidence that cannabis use is a contributory cause of psychosis.

METHOD

Using comparative analyses of similar evidence for the harmful effects of alcohol, tobacco, and amphetamine use, we considered the relation between observational evidence and action on cannabis. We examined arguments on the grounds of public health prudence for discouraging cannabis use by young individuals. With the assumption that the relation may be causal, we considered recommendations for policy in mental health services, health education, and public policy toward cannabis.

RESULTS

The observational evidence and biological plausibility of the hypothesis that cannabis is a contributory cause of psychosis is at least as strong as evidence for causal relations between heavy alcohol and amphetamine use and psychosis. On public health grounds, there is a good case for discouraging cannabis use among adolescents and young adults. It remains uncertain how best to discourage use and at whom campaigns to reduce cannabis use should be targeted.

CONCLUSIONS

We should discourage young adults seeking treatment in mental health services from using cannabis and inform them of the probable mental health risks of cannabis use, especially of early and frequent use. We must exercise caution in liberalizing cannabis laws in ways that may increase young individuals' access to cannabis, decrease their age of first use, or increase their frequency of cannabis use. We should consider the feasibility of reducing the availability of high-potency cannabis products.

Cannabis use and psychosis

This paper reviews evidence on two hypotheses about the relationship between cannabis use and psychosis. The first hypothesis is that heavy cannabis use may cause a "cannabis psychosis"-a psychosis that would not occur in the absence of cannabis use, the symptoms of which are preceded by heavy cannabis use and remit after abstinence. The second hypothesis is that cannabis use may precipitate schizophrenia, or exacerbate its symptoms. Evaluation of these hypotheses requires evidence of an association between cannabis use and psychosis, that is unlikely to be due to chance, in which cannabis use precedes psychosis, and in which we can exclude the hypothesis that the relationship is due to other factors, such as other drug use, or a personal vulnerability to psychosis. There is some clinical support for the first hypothesis. If these disorders exist they seem to be rare, because they require very high doses of THC, the prolonged use of highly potent forms of cannabis, or a pre-existing (but as yet unspecified) vulnerability. There is more support for the second hypothesis, in that a large prospective study has shown a linear relationship between the frequency with which cannabis has been used by age 18 and the risks over the subsequent 15 years of a diagnosis of schizophrenia. It is still unclear whether this means that cannabis use precipitates schizophrenia, whether it is a form of "self-medication", or whether the association is due to the use of other drugs, such as amphetamines, which heavy cannabis users are more likely to use. There is stronger evidence that cannabis use can exacerbate the symptoms of schizophrenia. Mental health services should identify patients with schizophrenia who use alcohol, cannabis and other drugs and advise them to abstain or to greatly reduce their drug use.

Cannabis use and psychotic disorders: an update

This paper evaluates three hypotheses about the relationship between cannabis use and psychosis in the light of recent evidence from prospective epidemiological studies. These are that: (1) cannabis use causes a psychotic disorder that would not have occurred in the absence of cannabis use; (2) that cannabis use may precipitate schizophrenia or exacerbate its symptoms; and (3) that cannabis use may exacerbate the symptoms of psychosis. There is limited support for the first hypothesis. As a consequence of recent prospective studies, there is now stronger support for the second hypothesis. Four recent prospective studies in three countries have found relationships between the frequency with which cannabis had been used and the risk of receiving a diagnosis of schizophrenia or of reporting psychotic symptoms. These relationships are stronger in people with a history of psychotic symptoms and they have persisted after adjustment for potentially confounding variables. The absence of any change in the incidence of schizophrenia during the three decades in which cannabis use in Australia has increased makes it unlikely that cannabis use can produce psychoses that would not have occurred in its absence. It seems more likely that cannabis use can precipitate schizophrenia in vulnerable individuals. There is also reasonable evidence for the third hypothesis that cannabis use exacerbates psychosis.

Clinical interventions for severe mental illness and co-occurring substance use disorder

In order to more effectively treat substance use disorders in persons with severe mental illness, integrated treatment models have been developed for these 'co-occurring disorders.' The nature of clinical services provided in these programs is described in this article, with brief attention to research on these programs. Clinical services are generally guided by a stage model of change, in which the client's motivation to change (or stage of treatment: engagement, persuasion, active treatment, relapse prevention) informs the optimal selection of appropriate interventions. Psychotherapeutic services for co-occurring disorders include a range of individual (motivational interviewing, cognitive-behavioral counseling), group (stage-wise groups, social skills training, self-help), and family (single family, multifamily formats) interventions. Supplementary interventions are also commonly provided, including psychopharmacological, residential, coerced and involuntary, and vocational rehabilitation. Access to a range of different interventions for co-occurring disorders may improve the ability of clinicians to engage and tailor treatment to meet clients' unique needs. The research base supporting integrated treatment for co-occurring disorders is limited at this time owing to the small number of methodologically rigorous studies from which to draw conclusions. Nevertheless, the available evidence suggests that integrated treatment programs improve outcomes compared with nonintegrated approaches, and that more research is needed to evaluate the benefits of these programs.

Nurses' knowledge, attitudes and beliefs regarding substance use: a questionnaire survey

A questionnaire on nurses' knowledge, attitudes, beliefs and practises regarding substance use was distributed to 302 nurses in Victoria. One hundred and thirty-four returned the questionnaire, giving an overall response rate of 44.3%. The survey results showed that although knowledge and skill gaps exist in assessment and management of alcohol and drug problems, overall knowledge levels were adequate. Although positive attitudes towards substance use were expressed, specific educational programs to enhance nurses' skills in assessment and management of substance-related disorders may be beneficial.

Contrasting views and experiences of health professionals on the management of comorbid substance misuse and mental disorders

OBJECTIVES

To determine opinions and experiences of health professionals concerning the management of people with comorbid substance misuse and mental health disorders.

METHOD

We conducted a survey of staff from mental health services and alcohol and drug services across Queensland. Survey items on problems and potential solutions had been generated by focus groups.

RESULTS

We analysed responses from 112 staff of alcohol and drug services and 380 mental health staff, representing a return of 79% and 42% respectively of the distributed surveys. One or more issues presented a substantial clinical management problem for 98% of respondents. Needs for increased facilities or services for dual disorder clients figured prominently. These included accommodation or respite care, work and rehabilitation programs, and support groups and resource materials for families. Needs for adolescent dual diagnosis services and after-hours alcohol and drug consultations were also reported. Each of these issues raised substantial problems for over 70% of staff. Another set of problems involved coordination of client care across mental health and alcohol and drug services, including disputes over duty of care. Difficulties with intersectoral liaison were more pronounced for alcohol and drug staff than for mental health. A majority of survey respondents identified 13 solutions as practical. These included routine screening for dual diagnosis at intake, and a range of proposals for closer intersectoral communication such as exchanging client information, developing shared treatment plans, conducting joint case conferences and offering consultation facilities.

CONCLUSIONS

A wide range of problems for the management of comorbid disorders were identified. While solution of some problems will require resource allocation, many may be addressed by closer liaison between existing services.

Cannabis use and psychosis: a review of clinical and epidemiological evidence

OBJECTIVE

This paper evaluates evidence for two hypotheses about the relationship between cannabis use and psychosis: (i) that heavy cannabis use causes a 'cannabis psychosis', i.e. a psychotic disorder that would not have occurred in the absence of cannabis use and which can be recognised by its pattern of symptoms and their relationship to cannabis use; and (ii) that cannabis use may precipitate schizophrenia, or exacerbate its symptoms.

METHOD

Literature relevant to drug use and schizophrenia is reviewed.

RESULTS

There is limited clinical evidence for the first hypothesis. If 'cannabis psychoses' exist, they seem to be rare, because they require very high doses of tetrahydrocannabinol, the prolonged use of highly potent forms of cannabis, or a preexisting (but as yet unspecified) vulnerability, or both. There is more support for the second hypothesis in that a large prospective study has shown a linear relationship between the frequency with which cannabis had been used by age 18 and the risk over the subsequent 15 years of receiving a diagnosis of schizophrenia.

CONCLUSIONS

It is still unclear whether this means that cannabis use precipitates schizophrenia, whether cannabis use is a form of 'self-medication', or whether the association is due to the use of other drugs, such as amphetamines, which heavy cannabis users are more likely to use. There is better clinical and epidemiological evidence that cannabis use can exacerbate the symptoms of schizophrenia.