Prevalence of illicit drug use

A wide range of population-based and clinical studies in the literature consistently demonstrate that substance use/dependence is one of the most common mental health-related disorders (Reference Cohen, Runciman and WilliamsCohen et al, 1999; Reference Coulthard, Farrell and SingletonCoulthard et al, 2002; Reference Crawford, Crome and ClancyCrawford et al, 2003). A national study of psychiatric comorbidity in the UK found that the prevalence of dependence on any drug was 4% and dependence on cannabis was reported most often at 3% (Reference Coulthard, Farrell and SingletonCoulthard et al, 2002). Drug-dependent individuals were more likely to be receiving current treatment and to have spoken to a general practitioner (GP) about mental health problems or to have used community services.

A variety of studies have consistently confirmed the clear association between mental ill health and substance misuse (Table 1). Affective disorders, personality difficulties, eating problems and attention-deficit hyperactivity disorder are all related to substance misuse. Substance misuse is also a powerful predictor of suicide. Childhood psychiatric disorders are very likely to continue into adulthood and they are often exacerbated by substance misuse, which is increasingly prevalent in young people. These studies argue powerfully for the need to include screening for substance misuse as part of any comprehensive psychiatric treatment plan. Skilled assessment and effective treatment of substance misuse may be important in the prevention and alleviation of disabling and life-threatening comorbid psychiatric conditions.

Table 1 Prevalence of illicit drug misuse in psychiatric patients

Source	Condition	Population	Country	Prevalence
Reference Appleby, Dyson and LuchinsAppleby et al, 1997	Any psychiatric disorder	Adult in-patients	UK	25%
Reference McCann, Simpson and RiesMcCann et al, 2000	Attention-deficit hyperactivity disorder	Adults	USA	33.8%
Reference Carey and CorreiaCarey & Correia, 1998	Schizophrenia Bipolar disorder	Adults Adults	USA USA	47% 56%
Reference Martino, Grilo and FehonMartino et al, 2000	Any psychiatric disorder	Adolescent in-patients	USA	Up to 50%

Despite these reported prevalence rates, substance use disorders are not being identified by hospital doctors: of 2347 in-patients referred consecutively to the consultation liaison psychiatry services of four general teaching hospitals in Australia, over half were diagnosed by psychiatrists as having a substance use disorder that had been missed by the referring doctor (Reference Smith, Clarke and HandrinosSmith et al, 1995; Reference Wolford, Rosenberg and DrakeWolford et al, 1999). Above all, diagnoses are missed because screening does not routinely occur (Reference Carey and CorreiaCarey & Correia, 1998).

Older people are a major target group that has been largely omitted from drug screening in hospitals. Part of the reason for this neglect may stem from the apparently low prevalence of illicit drug use among older people: a major study in the USA found that the lifetime prevalence of dependence on illicit drugs among people over 60 years of age was 1% (Reference Crome and CromeCrome & Crome, 2005; Reference Crome and BloorCrome & Bloor, 2006a ,Reference Crome and Bloor b ,c). However, this figure is probably an underestimate, and may increase as currently young and middle-aged addicts grow older.

It is questionable whether the routine screening of all hospital in-patients is productive: it might be best to target accident and emergency, trauma or general psychiatric patients. A wider debate surrounds the emphasis on identification and treatment of people in ‘high-risk’ groups through more universal prevention and screening initiatives aimed at the larger percentage of drug users, in whom behavioural change at an early stage may be more effective (Reference RoseRose, 1981; Reference KreitmanKreitman, 1986; Reference StockwellStockwell, 1999).

There remains a need for longitudinal, multidisciplinary shared assessment tools as an approach to enhance the understanding of the patterns and severity of coexisting substance misuse and psychiatric disorder and provide pointers for novel treatment interventions.

Enhancing accuracy of diagnosis and effective management

More detailed assessment, leading to a diagnosis if appropriate, is important to the development of a treatment plan (Reference Carey and CorreiaCarey & Correia, 1998). If substance misuse is undiagnosed, management of an individual's psychiatric disorder is likely to prove more difficult, less effective and more costly. The issues that need to be thought through in the process of screening include whether the level of drug use is likely to be harmful to the patient and family; whether screening can reveal opportunities for advice, counselling, other intervention and referral; how this might affect the patient and family; whether there are resources available to meet this need; and finally whether the screening process and/or detection of illicit substance use may affect the patient–doctor relationship.

If it is to be effective, routine screening must be integrated into everyday clinical practice and, as questionnaires or other methods must be acceptable to hospital staff and patients, it must be quick. Although the fact that illicit substance use is illegal seemingly poses additional ethical dilemmas, it is the duty of the medical profession ‘to maintain a good standard of practice and care’ while respecting the patient's rights (General Medical Council, 2001). The extension of the role of hospital staff to include routine screening may encounter both structural and attitudinal barriers, as described later, although this may be related to low confidence owing to lack of competence and a concern regarding poor channels of communication and the limited resources of drug services (Reference Herring and ThomHerring & Thom, 1999; Royal College of Physicians, 2001).

What is screening?

The process of assessing a person for possible drug use can be divided into a series of phases of increasing complexity (Box 1). One such classification views the process as having three stages (Effective Interventions Unit, 2003):

1. 1 simple assessment (or screening);

2. 2 comprehensive assessment;

3. 3 specialist (or in-depth) assessment.

Assessment is usually differentiated from screening by the fact that an assessment will lead to the formulation of a treatment plan, whereas screening only identifies the existence of a problem.

The value of using screening and assessment in general psychiatry was illustrated in a review of the effects of introducing such a system into an in-patient psychiatric setting (Reference Prochaska, Gill and HallProchaska et al, 2005). The increased emphasis on the recognition of substance misuse problems led to a doubling of referrals to specialist services and a 100% increase in the inclusion of substance misuse issues in care plans.

Screening techniques

A number of screening methods for illicit drug use are available (Box 2). The method chosen depends on the purpose, the setting, the nature of the target group and the technology and resources available for the screening programme. No one method is intrinsically better than another: there are advantages and disadvantages to each (Box 3).

Although several of the instruments described below have been tested in more than one country and with more than one sample of patients, the validity, appropriateness and acceptability of an instrument may still require further exploration to meet the particular screening needs and situation. Just as one screening approach is not necessarily better than another, so too it is not possible to state categorically that one screening instrument is more appropriate than another.

As already mentioned, screening and assessment are not the same thing: screening is an initial, relatively simple assessment, which generally provides a basic indication of health status, and can be conceptualised as the prelude or preliminary part of an ongoing, and sometimes protracted, process.

Self-completion questionnaires and rating scales

The advantages of using a screening or assessment tool are that recording is standardised, the instrument is ‘tried and tested’, a checklist of domains ensures that important issues are covered, and multidisciplinary professionals have a common shared understanding of what has been assessed (Box 4). This can prove useful in the organisation of the management plan. Furthermore, if tools are repeatedly used over time, results can be utilised to demonstrate progress to the patient and to measure outcome.

Instruments do need to cover a range of substances and take account of the emergence of new drugs. They must also address the heterogeneity of the drug-using population (e.g. by age-group, gender, and the presence of mental illness or particular medical conditions) and take account of a range of associated problems (in particular comorbidity). These requirements have influenced the development of different instruments (Boxes 5 and 6).

Box 4 Criteria for the evaluation of rating scales (Reference Gunthner and StetterGunthner & Stetter, 1996)

Reliability	Test results should be consistent across raters and across time
Validity	The scale should measure what it is supposed to measure
Sensitivity	The scale should detect a target behaviour or problem when it is present: the lower the sensitivity, the higher is the number of false negatives (individuals with the behaviour who are not identified)
Specificity	The scale should accurately identify people who do not display the target behaviour or problem: the lower the specificity, the higher is the number of false positives (individuals who do not have the behaviour who are erroneously identified as having it)
Effectiveness	According to the dimensions listed above
Efficiency	It should be cost-effective to administer the scale
Acceptability	The scale should be accepted by the target population as well as by those who administer it
Appropriateness of design and construction	In the development of the scale: on what basis (theoretical or empirical) were the items selected; was the sample population well-defined; and was the sample size sufficient to ensure at least a preliminary standardisation?

Biological markers

To corroborate both the verbal history provided by the patient, carers and professionals, and clinical findings, biochemical tests on blood, saliva, sweat, urine and hair can be undertaken (Reference Drummond and GhodseDrummond & Ghodse, 1999; Reference Wolff, Farrell and MarsdenWolff et al, 1999a ,Reference Wolff, Welch and Strang b ). In clinical practice, urinalysis (Box 7) and, more recently, saliva analysis are most commonly used to test for drugs.

Box 7 Detection times for urine screening

Cocaine	12–72 h
Amphetamine	2–4 days
Heroin	2–4 days
Codeine	2–4 days
Cannabis	up to 30 days
Diazepam	30 days

Drug users are rarely required to give urine samples under the direct supervision of clinical staff, but the temperature of the specimen can be judged when it is handed over. A simple pH test strip can confirm that the sample is compatible with urine. If in doubt, it is usually possible to ask for another sample soon after the first. Cannabis, methadone and long-acting benzodiazepines may remain in the urine for a week or longer, but other drugs may not be found after 48–72 h. Thus, if drugs are not detected, it does not necessarily indicate that the individual has not been using. If a patient is assessed as being dependent, the clinical picture may be that of a withdrawal syndrome; every drug has a specific set of criteria by which withdrawal can be diagnosed.

There are technical and practical difficulties in the use of biological markers and in the interpretation of results. These include ensuring a secure ‘chain of custody’ from initial collection to final disposition in order to guarantee the accurate attribution of a sample to a specified individual, the occurrence of false-negative and false-positive identification, the variability between substances in duration of detectability from a few hours to 10 days or more, the problem of passive contamination (e.g. of scalp hair), the need to ensure appropriate, rigorously applied laboratory testing procedures, and the existence of different thresholds and cut-off points in establishing positive identification (Reference Wolff, Farrell and MarsdenWolff et al, 1999a ,Reference Wolff, Welch and Strang b ).

Issues and concerns

Implementation of screening

What happens to the patient after screening is especially pertinent, particularly with regard to the provision of appropriate facilities for individuals who are identified as drug dependent or at risk of becoming so. Both professionals and patients may regard placement in a general psychiatric ward as unsuitable, and exposure to judgemental attitudes among staff is a continuing concern. Reference Appleby, Dyson and LuchinsAppleby et al (1997) have commented on the importance of aftercare, reporting ‘a general inattention to the post discharge needs of these individuals’. Screening for substance use seemed to increase staff awareness of substance use disorders, but did not enhance psychiatric patients’ access to community services.

Conclusions

Declaration of interest

None.

MCQs

1. 1 It is important to screen for drug problems in a general hospital because:

   1. a drug use has reached a plateau in the UK

   2. b drug use is more likely to be the consequence of the presenting problems than the cause

   3. c drug use is over-investigated in hospital

   4. d drug use is overreported

   5. e drug use is underreported.

2. 2 Drug dependence is likely to be associated with:

   1. a fewer presentations in primary care

   2. b a missed diagnosis by general hospital physicians

   3. c effective treatment if identified

   4. d fewer consultations with GPs about mental health issues

   5. e suicide.

3. 3 Older people with drug problems:

   1. a access treatment for substance use problems regularly

   2. b may develop dependence as readily as younger adults

   3. c use multiple prescription drugs

   4. d are likely to increase in number

   5. e are overestimated in general population surveys.

4. 4 The following groups of patients should be targeted for screening:

   1. a trauma

   2. b accident and emergency

   3. c general psychiatric

   4. d older people

   5. e young people.

5. 5 Screening:

   1. a usually involves only one instrument, which screens for a particular substance

   2. b and assessment are the same thing

   3. c usually involves the use of a structured questionnaire

   4. d usually involves the testing of hair

   5. e may identify drug-related problems in patients who present with problems other than drug dependence.

MCQ answers

1		2		3		4		5
a	F	a	F	a	F	a	T	a	F
b	F	b	T	b	F	b	T	b	F
c	F	c	T	c	T	c	T	c	F
d	F	d	F	d	T	d	T	d	F
e	T	e	T	e	F	e	T	e	T