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Department of Psychiatry, University of Cambridge
Cameo, Cambridgeshire and Peterborough Mental Health Partnership NHS Trust
Department of Psychiatry, University of Cambridge
Cameo, Cambridgeshire and Peterborough Mental Health Partnership NHS Trust
Department of Psychiatry, University of Cambridge, Cambridge, UK
Correspondence: Correspondence: Dr Jennifer Barnett, Department of Psychiatry, Box 189, Addenbrooke’s Hospital, Cambridge CB2 2QQ, UK. Email: jhb32{at}cam.ac.uk
Declaration of interest None. Funding detailed in Acknowledgements.
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMETHODRESULTSDISCUSSIONACKNOWLEDGMENTSREFERENCES |
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Aims To characterise substance and alcohol use in an epidemiologically representative treatment sample of people experiencing a first psychotic episode in south Cambridgeshire.
Method Current and lifetime substance use was recorded for 123 consecutive referrals to a specialist early intervention service. Substance use was compared with general population prevalence estimates from the British Crime Survey.
Results Substance use among people with first-episode psychosis was twice that of the general population and was more common in men than women. Cannabis abuse was reported in 51% of patients (n=62) and alcohol abuse in 43% (n=53). More than half (n=68, 55%) had used Class A drugs, and 38% (n=43) reported polysubstance abuse. Age at first use of cannabis, cocaine, ecstasy and amphetamine was significantly associated with age at first psychotic symptom.
Conclusions Substance misuse is present in the majority of people with first-episode psychosis and has major implications for management. The association between age at first substance use and first psychotic symptoms has public health implications.
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMETHODRESULTSDISCUSSIONACKNOWLEDGMENTSREFERENCES |
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METHOD |
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TOPABSTRACTINTRODUCTIONMETHODRESULTSDISCUSSIONACKNOWLEDGMENTSREFERENCES |
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Sample
The sample comprised consecutive referrals to the Cameo service between
June 2002 and June 2005. Inclusion criteria were the presence of positive or
negative symptoms for the first time, or previous episodes that had been
untreated, or were treated for less than 6 months with antipsychotic
medication. DSM–IV diagnoses were established using the Structured
Clinical Interview for DSM–IV (SCID;
First et al, 1997).
People with drug-induced psychoses and affective psychoses were included;
those with intellectual disability were excluded.
Inclusion criteria were altered during the study period as the Cameo service developed according to National Health Service guidance (Department of Health, 2001) and local implementation. The age range was initially 17–65 years but changed in April 2004 to 17–35 years. The catchment area comprised Cambridge City and South Cambridgeshire Primary Care Trust; the east Cambridgeshire area was included only up to November 2004. Incidence calculations took into account these demographic and geographical changes when determining the population-at-risk.
Assessments
Demographic information and the history of psychotic symptoms were
ascertained at the initial clinical interview. A second interview was then
conducted within 2 weeks of referral to the service, subject to the patient
being well enough to complete further assessments at this time. At this second
assessment, the SCID interview (First
et al, 1997) was completed by a researcher trained in its
use, and substance use assessed using the St George’s Substance Abuse
Assessment Questionnaire (Ghodse,
2002). Patients indicated if they had ever used any of the
following: alcohol, cannabis, solvents, heroin, methadone, crack/cocaine,
ecstasy, barbiturates, benzodiazepines, amphetamines, hallucinogens, or
ketamine. Patients were asked the age at which they had first used each
substance and the frequency of substance use over the past 30 days. Any
features of dependence were identified. Lifetime substance use was classified
according to DSM–IV criteria into no use, use, and abuse or
dependence.
Four measures of illness duration were extracted from patient and carer reports and case notes, where available. These were chosen to cover a range of the possible conceptions of illness duration (Norman & Malla, 2001). Where reports from different sources conflicted, the longer duration was taken. The four measures were as follows: (a) Duration of untreated psychosis (DUP) for the index episode: the time in months that psychotic symptoms were present without remittance before treatment was initiated for the index episode; (b) duration of untreated illness for the index episode: the time in months before treatment that some discernible change in behaviour or well-being had been present without remittance for the index episode; (c) age at first ever psychotic symptom: the age at which the first-ever psychotic symptom was experienced according to patient report; (d) lifetime duration of psychosis: the age at the time of assessment minus the age at first psychotic symptom. This represented an approximate measure of the lifetime duration of psychotic experiences.
The majority of patients assessed in the Cameo service during this period underwent a cognitive assessment (see Barnett et al, 2005). Premorbid IQ was estimated for patients who were native English speakers (n=90) using the National Adult Reading Test (NART; Nelson, 1982).
Participants gave informed consent to be interviewed and the procedure for using routinely gathered clinical information to generate aggregate research reports was approved by the Cambridge Local Research Ethics Committee.
Expected psychosis incidence
We estimated the extent to which our sample represented the expected number
of incident cases of clinically relevant psychoses by reference to published
data and knowledge of our population-at-risk. The age- and gender-specified
incidence of all psychoses from the Nottingham centre of the ÆSOP study
(Kirkbride et al,
2006) were used as the basis to predict the incidence of
first-episode psychosis in the population served by Cameo. The Nottingham
incidence rates by gender and 5-year age band were applied to similarly
stratified estimates of our population-at-risk ascertained from the 2001 UK
census (Office for National Statistics,
2003). This generated an expected number of incident psychosis
cases adjusted for age and gender, with which we compared our observed number
of cases over the period of the survey. Changes in age range and catchment
area as the service evolved were taken into account; numbers of expected cases
for the periods June 2002 to April 2004, April 2004 to November 2004 and
November 2004 to June 2005 were calculated separately and summed for the total
study period.
Drug use prevalence
The 2002–03 British Crime Survey
(Condon & Smith, 2003) was
used as a basis for comparison of substance use in people with first-episode
psychosis and the general population. This is a large national survey of
adults living in a representative cross-section of households in England and
Wales. Since 1996, the survey has included questions on drug use and reports
the prevalence of substance use for those aged 16–59 years. Since drug
use varies considerably with age, age-adjusted general population estimates
were produced by multiplying the prevalence in the British Crime Survey by the
proportion of Cameo patients falling within the survey’s published age
ranges (16–24, 25–34 and 35–59 years). Under the Misuse of
Drugs Act 1971 the following substances are classified as Class A drugs:
opiates, cocaine, hallucinogens and ecstasy. The British Crime Survey
distinguishes between other substances and Class A drugs; we followed the same
distinction in our sample. Enhanced data are available within the British
Crime Survey for substance use (excluding alcohol) among 16- to 24-year-olds.
This age group was considered separately in our study to take advantage of
this and because of the increased risk for onset of psychosis within this age
group.
Statistical analysis
Comparisons of the proportion of men and women who had used each substance
were made by calculating odds ratios with 95% confidence intervals. Measures
of illness duration deviated from the normal distribution according to the
one-sample Kolmogorov–Smirnov test. Associations between NART-estimated
IQ, measures of illness duration and age at first use of each drug were
therefore made using Spearman’s rho. Mann–Whitney U-tests
were used to compare men and women for the age at first use of each
substance.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMETHODRESULTSDISCUSSIONACKNOWLEDGMENTSREFERENCES |
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Sample characteristics
Data on substance use were available from 123 of the 139 people with
first-episode psychosis referred to Cameo during this period (88%). The
remainder (n=16) declined to participate in the assessment at which
substance use was reported. Of those who did complete the assessments, 93
(75.6%) were men, with a median age of 25 years (range 17–65). Mean
NART-estimated premorbid IQ was 110.0 (s.d.=8.3, range 92–124). Of
patients who underwent the SCID interview, only 1 received an initial
diagnosis of drug-induced psychotic disorder. The most common initial
diagnoses were schizophrenia and schizophreniform psychoses (n=35);
mood disorders (n=37) and psychotic disorder not otherwise specified
(n=37), including cases where it was unclear whether the psychosis
was drug-induced.
Lifetime substance use
Lifetime substance use of the sample is shown in
Table 1 and
Fig. 1. In some cases
participants did not disclose their use, or otherwise, of every substance; for
this reason sample sizes vary between substances.
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Alcohol
Alcohol use was almost universal: only 1 participants out of 123 reported
never having consumed alcohol. Nearly half the sample (n=53, 43.1%)
met DSM–IV criteria for alcohol abuse or dependence at some point in
their life, with the remainder (n=69, 56.1%) reporting alcohol use
but not abuse. Median age at first use was 15 years (range 5–30
years).
Cannabis
Cannabis was the next most commonly used substance. Of 122 participants, 98
(80.3%) reported using cannabis at some time in their life. More than half
(n=62, 50.8%) met DSM–IV criteria for cannabis abuse or
dependence. Age at first use of cannabis ranged from 7 to 30 years (median 15
years).
Class A drugs
Class A drug use was common, and included use of ecstasy (n=57),
hallucinogens (n=52), crack or cocaine (n=49) and heroin
(n=20). Methadone use was uncommon (n=4).
Other substance use
Amphetamine use was common (n=49). Rarely used substances included
solvents (n=16), ketamine (n=7) and benzodiazepines
(n=6). There were no reports of barbiturate use.
Substances used by fewer than 20 patients were not subjected to subsequent analyses because of power limitations.
Gender differences
Men with first-episode psychosis were slightly more likely than women to
have used heroin (OR=1.3, 95% CI 1.2–1.4), and three times more likely
to have used ecstasy (OR=3.4, 95% CI 1.4–8.4) or hallucinogens (OR=3.4,
95% CI 1.3–8.6) during their life. There was also a trend towards more
cocaine use in men (OR=2.3, 95% CI 0.9–5.5). Men and women did not
differ in amphetamine or cannabis use. Comparisons of usage between men and
women were not possible for solvents, ketamine, benzodiazepines and methadone
because of the small number of patients (n<20) who had used these
substances.
There were no significant differences between men and women in the age at first use of any substances. There was a trend towards earlier first use of cannabis in men (mean 15.6 years) than women (mean 17.9 years; z=–1.90, P=0.06).
Estimated premorbid IQ
NART-estimated IQ was not associated with any of the measures of duration
of illness or with age at first use of any substance. Groups defined by the
use or non-use of each substance did not differ in their NART-estimated
IQ.
Polysubstance abuse
A high proportion of participants met DSM–IV criteria for lifetime
abuse or dependence for more than one substance
(Fig. 2).
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Substance use in previous 30 days
Of our participants with first-episode psychosis, 29% reported using one or
more substances (other than alcohol) within the previous 30 days compared with
13% of the general population (age-adjusted prevalence; see
Fig. 4). Almost all of the
substance use in the preceding month was accounted for by cannabis: 29% of
patients compared with 12% of the general population (age-adjusted
prevalence). Seven patients (5.9%) had used Class A drugs within the past
month (age-adjusted national prevalence 2.8%) and an additional 2 patients
(1.8%) had used amphetamines during this period (age-adjusted national
prevalence 1.1%).
Duration of illness and age at first substance use
Spearman’s correlations were used to determine the association
between duration of illness and age at first use of substance, for those
substances for which data were available for at least 20 participants
(Table 1). Age at first
psychotic symptom was positively associated with age at first use of cannabis,
cocaine, ecstasy and amphetamines, but not alcohol or hallucinogens. There
were negative associations between duration of untreated psychosis for this
episode and age at first use of amphetamines and hallucinogens, and between
hallucinogen use and duration of illness for this episode. This suggests that
patients who start taking drugs at a younger age take longer to seek treatment
after experiencing their first psychotic symptom. No associations were found
between lifetime duration of untreated psychosis and age at first drug
use.
The age at which patients first used each substance is shown in Fig. 5. For alcohol and cannabis, the peak age for first use was between 12 and 14 years, whereas for ecstasy, amphetamines, hallucinogens and, to a lesser extent, cocaine, the peak age for first use was between 14 and 19 years. In the majority of patients referred to the Cameo service, first substance use was several years prior to the first psychotic symptom.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMETHODRESULTSDISCUSSIONACKNOWLEDGMENTSREFERENCES |
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The high prevalence of substance use among people with first-episode psychosis is in accordance with previously published data from the UK (Cantwell et al, 1999), North America (Van Mastrigt et al, 2004) and Australia (Wade et al, 2006). A recent review (Green et al, 2005) based on 53 treatment samples found prevalence estimates of cannabis use of 42% for lifetime use (Cameo prevalence 80%) and 23% for current use (Cameo prevalence 29%).
The high prevalence of substance use in our participants with first-episode psychosis is particularly notable given that we estimate that the sample is representative of all people who experience a clinically relevant first psychotic illness. This is interesting with respect to the general pattern where population-based samples produce lower estimates of substance use than samples recruited from clinics (Green et al, 2005). However it should be noted that substance use data were not available for the entire sample, and that we did not include people with psychotic symptoms or syndromes who did not present to services, or a small number of people with first-episode psychosis that were not referred to the service.
The increased prevalence of substance misuse in first-episode psychosis relative to the general population may even have been underestimated in this study. Underdetection of substance use among psychiatric patients is widespread: a UK study found that substance use among acute admissions could be detected by urinalysis twice as often as was mentioned in medical or nursing notes (Ley et al, 2002). A second study compared the extent of substance use as reported by patients with schizophrenia, co-informants such as a relative or keyworker, and by hair and urinalysis (McPhillips et al, 1997) and found severe underreporting by patients for cocaine and amphetamines, although self-report of cannabis use was both more frequent and more accurate, as judged by informant report and urinalysis.
People with first-episode psychosis might be wary of admitting to excessive substance use in case it affects their clinical management, diagnosis, or simply because it might elicit a judgemental response from staff. In addition, estimates of drug use in the past month may be reduced in current in-patients referred to the Cameo service relative to their normal levels of drug use, although we note that drug use among inpatients is a growing problem.
Substance use in first-episode psychosis might be expected to be more common than in the general population since the sample includes an excess of young, single men; factors associated with increased substance use (Chivite-Matthews et al, 2005). South Cambridgeshire is relatively affluent but has a disproportionate number of young adults (Office for National Statistics, 2003). Although the ÆSOP and British Crime Survey data are the best available for comparison, the Cameo catchment area clearly differs from the Nottingham and national samples in some ways (for example, in ethnicity and urbanicity). None the less, it seems unlikely that the demography of the catchment area would explain the high levels of substance use in our sample.
Significance of substance use
The high prevalence of substance use reported in this sample of people with
first-episode psychosis has important clinical implications. Substance misuse
in people with psychotic disorders is robustly associated with non-adherence
to treatment (Weiss et al,
2002; Nose et al,
2003; Margolese et
al, 2004) and poorer outcomes
(Verdoux et al,
2005), whereas a reduction in substance use after diagnosis is
associated with a reduction in subsequent admissions and psychotic symptoms
(Sorbara et al, 2003;
Lambert et al, 2005).
Follow-up (15 months) from a similar service for first-episode psychosis
suggests that around three-quarters of patients with a lifetime diagnosis of
substance misuse will continue to misuse after the initiation of treatment
(Wade et al,
2006).
Identification and reduction of substance use and misuse should be a key therapeutic target for early intervention services and has implications for staff training. Management of cannabis misuse is not a focus of specialist substance misuse services and dual-diagnosis services tend to focus on chronic, not first-episode patients. This study suggests that dual-diagnosis services should become part of early intervention efforts. However, the current evidence base is scant; further treatment trials and the development of therapeutic strategies are clearly required.
There were associations between age at onset of psychosis and age at first substance use. A previous study found that cannabis use was predictive of earlier onset of schizophrenia (Veen et al, 2004) and a second study showed that early use of cannabis (prior to 16 years) was associated with both positive and negative dimensions of psychosis (Stefanis et al, 2004). Buhler et al (2002) attempted to clarify the precedence of heavy substance use, the onset of any schizophrenia symptoms (including negative symptoms) and the onset of psychotic symptoms. They found that first drug misuse and the onset of general symptoms tended to coincide, but there was no correlation between first drug misuse and the onset of psychotic symptoms. As in that study, our findings were partly confounded by the age of the participants (i.e. it was not possible to assess the association in those who were already psychotic but will in the future start using illicit substances). None the less, they do provide further evidence for an association between early substance use and onset of psychosis. From the public health standpoint, it seems clear that preventative measures regarding drug use need to be targeted at children in the preteenage years; our data suggest that the transition from junior to senior schools might be an important juncture
In the general population, people who smoke cannabis are more likely to become psychotic (Andreasson et al, 1987; Zammit et al, 2002). Early use may be particularly potent (Arseneault et al, 2002), which is consistent with our findings. However, there are a number of possible explanations for the association, including models where a common factor explains both substance use and psychosis, models where substance use is secondary to psychosis or where psychosis is secondary to substance use, and, theoretically, bi-directional models where psychosis and substance use interact in their causation and maintenance (Mueser et al, 1998; Fergusson et al, 2006). The associations between age at first substance use and age at first psychotic symptoms might be explained by any or all of these hypotheses; our data do not distinguish these alternatives.
An important implication of our results is that the prevalence of the use of substances other than cannabis is high and might be equally important. Recent debates regarding the legal status and safety of cannabis might have diverted attention from the importance of other substance misuse. The prevalence of cannabis use was, indeed, higher in people with first-episode psychosis than in the general population. However, the prevalence of other substance misuse, notably Class A drugs and, at the other end of the legal spectrum, alcohol was greater still. Although age at first cannabis use was significantly associated with age at onset of psychosis, associations between age at first use of cocaine, ecstasy, and amphetamines were even stronger. The high levels of polysubstance misuse and misuse of substances with a high potential for addiction are clinically and socially important, and should be the subject of further research. We did not assess the use of nicotine which might be linked with progression to other drugs, has serious health consequences itself and might even be linked to the underlying biology of psychosis.
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ACKNOWLEDGMENTS |
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TOPABSTRACTINTRODUCTIONMETHODRESULTSDISCUSSIONACKNOWLEDGMENTSREFERENCES |
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMETHODRESULTSDISCUSSIONACKNOWLEDGMENTSREFERENCES |
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Received for publication March 20, 2006. Revision received November 20, 2006. Accepted for publication December 8, 2006.
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, abuse
or dependence; 
, use but not
abuse; 
, never used.
, General population; 
, General
population; 
, Alcohol(n=93);
, cannabis (n=98);
, cocaine (n=46);
, ecstasy (n=56);
, amphetamine
(n=49); 
,
hallucinogen (n=49);
, first psychotic symptom
(n=88).