Chapter 12
Assessment and management of substance abuse comorbidity in people with schizophrenia
KEY POINTS
• Substance abuse and dependence are common amongst people with schizophrenia.
• An integrated framework is preferred for treatment delivery.
• Attention should also be given to adherence with antipsychotic medications.
• Long-acting injectable forms of antipsychotics should be considered.
• Clozapine might have a particular role in people with schizophrenia and substance abuse.
One of the major difficulties in assessing the impact of substances of abuse in people with schizophrenia lies in differentiating the effects of the substance from the core symptoms of schizophrenia. This is critical as it informs treatment. The next challenge is to engage the individual in a discussion about the impact of the substance of abuse on their physical and mental health and to motivate them to address their substance use. This chapter provides a framework for evaluation and engagement as well as outlining treatment options to assist people with schizophrenia and substance abuse comorbidity.
Differentiating substance-induced psychotic symptoms from schizophrenia
It is important to be clear about semantics. All too often clinicians talk of ‘drug-induced psychosis’ in someone who clearly has an underlying psychotic illness such as schizophrenia, but in whom there is a temporal association between an exposure to a substance of abuse and the manifestation of psychotic symptoms. In such individuals the preferred term is ‘drug-precipitated psychosis’, acknowledging the underlying psychotic predisposition. ‘Drug-induced psychosis’ should, in our view, be applied to those drug-induced toxidromes in which psychotic symptoms are present but which abate over a short period (usually 24–48 hours, depending upon the half-life of the particular drug) and there is no residuum.
It is not always easy to tease out the effects of a substance on mental state if the person continues to use the drug in question. A very careful longitudinal history with collateral, especially mapping periods of drug use and abstinence, and concomitant impact of mental state is critical. If possible, observation of the individual whilst not under the influence of drugs allows one to establish their ‘baseline’ mental state and functioning. Of course, one needs to manage withdrawal effects (see below) and in long-term users of long-half-life drugs such as cannabis to give sufficient time for the drug to clear the brain (this can take up to a month in the case of cannabis).
There are a number of useful clinical pointers regarding the differentiation of drug-induced psychoses from schizophrenia. These are summarized in Box 12.1.
Box 12.1 Clinical pointers differentiating schizophrenia from drug-induced psychosis
• Psychotic symptoms precede substance use
• Psychotic symptoms persist despite abstinence (a one-month cut-off is usually applied)
• Psychotic symptoms manifest even when substances are not used
• There is a personal past history of schizophrenia
• There is a family history of schizophrenia
Adapted with permission from Lubman, D.I., Sundram, S. Substance misuse in patients with schizophrenia: A primary care guide. Medical Journal of Australia, 178: S71–75. Copyright © 2003 Wiley. Data from Woody, G., Schuckit, M., Weinrieb, R., Yu, E. A review of the substance use disorders section of the DSM-IV. Psychiatr Clin North Am, 1993; 16: 21–32.
Treatment frameworks
Many commentators have pointed out the relative dearth of good-quality controlled trial evidence to support specific interventions for people with schizophrenia and substance abuse. In part this is due to the inherent difficulties in engaging and retaining such individuals in clinical trials, and also speaks to the complexity of the clinical picture, with severe psychotic symptoms intersecting with high volumes of use of (often) multiple drugs, and with other psychiatric and medical morbidities adding to the burden (see Chapter 12).
This lack of empirical data is compounded by treatment service structures that do not lend themselves to dealing with multiple problems simultaneously. In particular, drug and alcohol and mental health services are often under discrete governance and funding models and this leads all too often to either sequential or parallel care for people with schizophrenia who have drug use problems (see Box 12.2). Lubman and colleagues (2010) suggest that this might be adequate for people with milder forms of disorder, but it does not adequately meet the needs of those with severe and protracted disorders, where an integrated model is preferred. Such a model allows a comprehensive approach in a single service setting and ensures that each set of problems is addressed, along with acknowledgement of the interactions between them. Also, as Horsfall et al. (2009) point out, it is important to address basic issues such as finances and housing as part of a treatment plan.
Box 12.2 Overarching models of service delivery for people with schizophrenia and substance abuse
Adapted with permission from Lubman, D. I., King, J. A., Castle, D. J. (2010) Treating comorbid substance use in schizophrenia. International Review of Psychiatry, 22: 191–201.
Motivational interviewing
Motivational interviewing (MI) is employed widely in the drug and alcohol sector, as part of an engagement process and setting up a treatment plan. We consider it here in some detail separately from other psychosocial interventions, as we see it as a component part of a comprehensive treatment plan, rather than a complete treatment in itself. Other psychosocial treatments are discussed below. The idea of MI is to map the ‘stage of change’ of the individual and to have a discussion that serves to move them along the continuum towards acceptance of treatment (see Box 12.3). Baker et al. (2002) suggested that even very brief ‘opportunistic’ interventions can be successful, but their own study of 160 psychiatric inpatients with drug and alcohol problems (alcohol, cannabis and amphetamines) failed to show any benefit from a 30- to 60-minute manualized MI session in terms of engagement with a substance abuse specialist unit. Posited reasons for this disappointing outcome include the severity of the clinical state and the lack of ability to address the substance use issue within the mental health service. This reinforces the virtue of integrated service arrangements, as detailed above. Multisession MI interventions have been shown to have efficacy for some people, albeit the studies are not consistent (see Drake et al. 2008). It should also be emphasized that it often takes a number of ‘cycles’ of MI before traction is effected. Linking with cognitive behavioural and other approaches can enhance outcomes, as outlined below.
Box 12.3 Principles of MI techniques tailored to stage of change
Source: Data from Baker, A., Lewin, T., Reichler, H., et al (2002) Motivational interviewing among psychiatric in-patients with substance use disorders. Acta Psychiatrica Scandinavica, 106: 233–240; Lubman, D.I., Sundram, S. (2003) Substance misuse in patients with schizophrenia: A primary care guide. Medical Journal of Australia, 178: S71–75.
Psychosocial treatments
Drake and colleagues (2008) conducted a useful systematic review of psychosocial treatments for people with substance use and severe mental illness. They endorse the integrated approach outlined above and emphasize the benefits in terms of both access and individualization of care. The more recent Canadian Guidelines (Crockford and Addington 2017) are largely synergistic with these findings and suggestions and add the importance of involving families (where appropriate) in treatment planning and execution. Box 12.4 summarizes the interventions; the text follows Drake et al. (2008), to which article the reader is referred for original references.
Box 12.4 Summary of psychosocial interventions for substance use comorbidity in people with schizophrenia
• Intensive outpatient rehabilitation
Adapted with permission from Drake, R.E., O’Neal, E.L., Wallach, M.A. A systematic review of psychosocial research on psychosocial interventions for people with co-occurring severe mental and substance use disorders. Journal of Substance Abuse Treatment, 34: 123–138. Copyright (c) 2008 Elsevier.
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