Models of intervention and care for psychostimulant users, 2nd edition - monograph series no. 51

Assessment of comborbidity in psychostimulant users

Page last updated: April 2004

Determining an accurate diagnosis in people with co-occurring severe mental illness and substance use is a complex task. In the first instance, the clinician needs to take a careful history of psychiatric symptoms and the use of substances (see Table 15). Having established the temporal relationship between the onset of substance use and symptoms it is then possible to determine whether there have been changes in substance use over time, e.g., periods of abstinence or increased use and the impact that this had on symptoms. Zimberg (1999) developed a helpful typology to guide clinical practice. He distinguishes between three subgroups of comorbidity. The first, referred to as Type I: Primary psychiatric disorder, describes the case of a person whose psychiatric disorder clearly began before regular substance use and the substance use disorder is influenced by the course of the psychiatric disorder. One example may be of a person who uses amphetamines only during a manic episode. Type II: Primary substance use disorder occurs when the substance use clearly existed prior to the onset of the psychiatric disorder and the psychiatric symptoms are present only during active phases of substance use. Finally, Type III: Dual primary disorder occurs when both psychiatric and substance use disorders are present and do not coincide with one another in either onset or course.

In the case of psychostimulant use, both withdrawal and intoxication states have many similarities with mood and affective disorders. Amphetamine withdrawal is characterised by dysphoric mood, fatigue, sleep difficulties and psychomotor retardation, all symptoms that occur in depression. The agitation and anxiety that often occurs during psychostimulant intoxication and withdrawal share many features of an anxiety disorder (American Psychiatric Association, 1994). Symptoms that are similar to hypomania and mania can also be seen during amphetamine intoxication. If these symptoms clearly follow a substantial period of amphetamine use, for example, and remit over a two-week period, then a diagnosis of amphetamine-induced anxiety disorder or amphetamine-induced mood disorder is appropriate (Larson, 2002). Repeated, high-dose binge patterns of amphetamine use can result in a psychostimulant-induced psychosis that closely mimics symptoms of paranoid schizophrenia (Segal & Kuczenski, 1997; Segal & Kuczenski, 1999). If the symptoms resolve within a one-month period after the discontinuation of amphetamine use, then a diagnosis of amphetamine-induced psychosis is appropriate with either delusions or hallucinations listed as the predominant symptom (American Psychiatric Association, 1994). However, it is not always possible to distinguish at presentation whether the symptoms are drug-induced or are indeed part of a primary and pre-existing disorder that may have been exacerbated by substance use (e.g. Shaner et al., 1998).

The DSM-IV (American Psychiatric Association, 1994) provides diagnostic criteria that will enable a clinician to ascertain whether the patient is experiencing a substance-induced mental disorder. As the use of structured diagnostic interviews provides more accurate diagnoses than less structured clinical interviews across a range of disorders (e.g. Miller, Dasher, Collins, Griffiths & Brown, 2001), we recommend that such interview schedules are used whenever possible. Two possible diagnostic interviews are the Structured Clinical Interview for DSM (SCID, Spitzer et al., 1994) and the Composite International Diagnostic Interview (CIDI) developed by WHO (Wittchten, 1994). Both structured interviews are widely used in research settings, they are less often used in clinical settings although diagnostic accuracy is always enhanced when they are used. Thorough training in the administration of either structured interview is necessary in order to ensure that overall diagnostic accuracy is achieved (Ventura, Liberman, Green, Shaner & Mintz, 1998). Training in the administration of the CIDI can be obtained from the Clinical Research Unit for Anxiety Disorders, St. Vincents Hospital in Sydney, New South Wales.
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Once the presence or absence of particular symptoms has been established, it is often helpful to assess the severity of symptoms in order to quantify symptom change over time. The use of valid and reliable instruments that are sensitive to change over time is strongly recommended. Whilst a comprehensive review of potential measures is beyond the scope of this chapter, we have provided a brief overview of some available symptom measures that are widely used.

Symptom severity ratings for psychosis include the Positive and Negative Symptoms Scales (Kay, Opler & Lindenmayer, 1988) and the SANS and the SAPS (Kay et al., 1988). One of the most widely used is the Brief Psychiatric Rating Scale. The Brief Psychiatric Rating Scale (BPRS) (Overall & Gorham, 1962) is a clinical rating scale widely used in psychiatric practice. Ratings for each symptom are made after a brief (15-20 minutes) semi-structured interview. Each item is rated on a 7-point scale ranging from 'not present' to 'extremely severe'. The BPRS is a reliable and valid measure of symptom severity when used by trained mental health clinicians. There are also a number of measures for mood and anxiety symptoms. One such instrument that has been developed in Australia and is readily available is the Depression and Anxiety Stress Scales (Lovibond & Lovibond, 1995). Those in the public domain which may be used without cost but with due acknowledgement of their source are described in detail in Dawe et al. (2002).

There are a number of settings where psychostimulant users may present with clinically significant levels of psychotic or mood and anxiety symptoms in which the clinician is not able to conduct a structured diagnostic interview. Such settings may include needle and syringe programs, primary care settings, community mental health services or emergency departments. A screening instrument is particularly useful if the client presents with some or all of the following:

  • a strong family history of a mood disorder;
  • if there is a clear pre-existing history of a mood disorder; and
  • if the individual has ongoing significant affective symptoms after one month of abstinence.
The use of screening instruments such as the General Health Questionnaire (GHQ) is recommended to determine whether there are mood or anxiety disorders. In relation to determining possible psychosis or sub-clinical symptoms of psychosis a Psychosis Screener (Jablensky, McGrath, Castele, Gureje et al., 2000) may also be administered (see Table 16). In addition, below are some helpful practical tips adapted from the "Users' guide to speed" (see Table 17) (Topp et al., 2001). Practitioners treating methamphetamine users may also find it helpful to train their clients to recognise the early signs of drug-induced psychosis and to cut down their use in response to these signs and seek medical help if necessary.

Once the presence or absence of particular symptoms has been established, it may be helpful to ascertain whether there is a pre-existing disorder and to assess the severity of symptoms in order to quantify symptom change over time. The use of valid and reliable instruments that are sensitive to change over time is strongly recommended. Whilst a comprehensive review of potential measures is beyond the scope of this chapter, we have provided a brief overview of some available symptom measures that are widely used.

Table 15: Prompts in assessing the comorbidity of substance use disorder and psychiatric illness

Table 15 is presented as a list in this HTML version for accessibility reasons.
  • Ask for recent drug and alcohol use.

  • Consider the range of symptoms that the use of each identified substance may cause.

  • Determine whether substance use predated the psychiatric symptoms:
    1. How old were you when you first experienced ... (symptoms)?
    2. How old were you when you started using (substance) regularly1?

  • Has there been a time when you have not used (substance)?
    1. (If yes) How did this affect your (symptoms)?

  • Has there been a time when you have not experienced (symptoms)?
    1. (If yes) How did this affect your use of (substance)?

Adapted from Shaner, Roberts, Eckman, Racentein et al. (1998)
1 regular use defined as at least weekly use of substance.

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Table 16: Psychosis screener from Jablensky et al., 2000

Table 16 is presented as a list in this HTML version for accessibility reasons.
  1. Delusional mood
    1. Has the person ever felt something strange, unexplainable was going on?
      0 = No
      1 = Yes
    2. If yes, was this so strange that others would find it very hard to believe?
      0 = No
      1 = Yes

  2. Grandiose delusions
    1. Has the person ever believed they have special powers, talents that most people lack?
      0 = No
      1 = Yes
    2. If yes, do they belong to a group that believes they have special powers, talents?
      0 = No
      1 = Yes

  3. Delusions of reference/persecution
    1. Has the person ever felt people were too interested in them?
      0 = No
      1 = Yes
    2. If yes, did they feel harm might come to them?0 = No
      1 = Yes

  4. Delusions of control
    1. Has the person ever felt thoughts were directly interfered with, controlled by others?
      0 = No
      1 = Yes
    2. If yes, did this happen in a way others would find hard to believe, e.g. telepathy?
      0 = No
      1 = Yes

  5. Hallucinosis
    1. Has the person ever heard voices or had visions when there was no-one around?
      0 = No
      1 = Yes

  6. Diagnosis of Psychosis
    1. Has the person ever been prescribed psychotic medicine, diagnosed as psychotic by a doctor?
      0 = No
      1 = Yes
      Please specify:

  7. Rating of Psychosis by Key Worker
    1. Using clinical judgement, is this person psychotic or has ever been psychotic?
      0 = Definitely not
      1 = Possibly
      2 = Definitely
      Additional comments:
Top of pageNote: The cut-off point applied for recording a person as screen positive for psychosis is at least 2 positive items (Items 1–6) subject to the following provisos:
  • 'yes' to item 6 only and 'definitely positive' to item 7 = positive for psychosis;
  • 'yes' to item 6 and 'yes' to one other item 1- item 5 and 'maybe' in item 7 = positive for psychosis;
  • 'yes' to item 6 only and 'possibly' in item 7 = negative for psychosis.
If the clinician considers the person to have screened positive for psychosis, then ensure that appropriate referral is made.

Table 17: Tips for speed users (adapted from Topp et al., 2002)

Table 17 is presented as a list in this HTML version for accessibility reasons.

Have a break from speed if you:
  • Keep having odd thoughts that won't go away.
  • Feel overly suspicious of your friends or other people.
  • Are imagining things that aren't really there — seeing things that other people can't see or hearing things other people can't hear.
  • Often feel like other people are noticing you so that you begin to avoid people, especially strangers in public places.
  • Feel extreme jealousy.
  • Have used speed for more than three days in a row or have used it more than three weekends in a row.
  • If you are feeling anxious or depressed avoid using more speed, these may be warning signs of speed psychosis.
  • Try to get a few good nights sleep.

Factors affecting the reliability of self-report

As with any clinical assessment, the accuracy of the information obtained during the history is influenced by a number of factors including the rapport established between the client and the interviewer and the context or circumstances surrounding the interview. Additional factors need to be considered, however, in the case of a client with both a substance use disorder and suspected co-occurring mental health problems. Recent drug use and accompanying intoxication or the severity of withdrawal symptoms will influence the client's attention and concentration. Further, the presence of symptoms associated with psychosis will influence the amount of information a client may be prepared to divulge. For example, symptoms of suspiciousness and hostility that are sub-clinical symptoms of psychosis may reduce the likelihood of obtaining accurate information. The presence of acute psychotic symptoms such as delusions and hallucinations may reduce this even further. Managing the clinical situation and appreciating that aggressive or hostile features of the presentation may be due to a direct effect of amphetamine use rather than indications of other enduring personality features is always necessary. Whenever possible, interviews should be conducted across a period of days to determine the course of such features.

Quantitative measures of alcohol and other drug use

Obtaining information on drug consumption using well-validated and reliable instruments is good clinical practice. However, there are relatively few measures from the substance use field that have been validated in people with amphetamine use disorders. The Timeline Follow Back (TLFB, Sobell & Sobell, 1992) uses a calendar method to provide memory aids to help people reconstruct their recent drinking and drug use patterns and typically covers the last 30 days of use. This method has been used successfully in samples of people with schizophrenia-spectrum disorders (Carey, 1997), in people with cannabis use and early onset psychosis (Hides, Dawe, Kavanagh & Young, unpublished) and in amphetamine users attending a needle and syringe exchange program (Dawe, Saunders et al., unpublished). While the TLFB method provides a detailed picture of recent drug use, additional information regarding the age of onset of all substance use, age of regular use and periods of abstinence are also necessary. A more detailed description of other standardised measures of drug and alcohol use may be found in Carey et al., (Carey, 2002; Carey & Correia, 1998) and Dawe et al. (2002).

In addition to assessing recent frequency of use, it may be wise to consider severity of dependence. Diagnostic criteria for dependence can be found in the DSM-IV and ICD-10 under substance use disorders (see Chapter 1: Background to the monograph). A simple way to obtain an estimate of the current level of dependence is by using the Severity of Dependence Scale (see Table 18). This five-item scale has been validated against DSM-IV criteria for dependence and a cut-off score of greater than four was found to correspond to a diagnosis of severe amphetamine dependence (Topp & Mattick, 1997a).Top of page

Table 18: Severity of Dependence Scale (adapted from Gossop et al., 1995)

Table 18 is presented as a list in this HTML version for accessibility reasons.
  1. Have you ever thought your speed use is out of control?
    Never (0)
    Sometimes (1)
    Often (2)
    Always (3)

  2. Has the thought of not being able to get any speed really stressed you at all?
    Never (0)
    Sometimes (1)
    Often (2)
    Always (3)

  3. Have you worried about your speed use?
    Never (0)
    Sometimes (1)
    Often (2)
    Always (3)

  4. Have you wished that you could stop?
    Never (0)
    Sometimes (1)
    Often (2)
    Always (3)

  5. How difficult would you find it to stop or go without?
    Never (0)
    Sometimes (1)
    Often (2)
    Always (3)
Total score: