Departments of Psychiatry and Epidemiology and Biostatistics, University of Western Ontario, London, Ontario, Canada
School of Psychiatry and Behavioural Sciences, University of Manchester, Manchester, UK
Correspondence: Ross M.G. Norman, Room 113B, WMCH Building, 392 South Street, London, Ontario N6A 4G5, Canada. E-mail: rnorman{at}uwo.ca
* Based on a paper presented at the Third International Early Psychosis
Conference, Copenhagen, Denmark, September 2002.
1 We have omitted deHaan et al
(2000) from our discussion
because they relied entirely on reports solicited through a questionnaire in a
monthly magazine for relatives of patients with schizophrenia. Such a
procedure appears to allow little confidence in comparable standards for
estimation being used across cases.
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ABSTRACT |
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Aims To critically examine the evidence concerning DUP being related to treatment outcome and possible mediators of any such relationship.
Method A systematic review of studies in which DUP is assessed and its relationship to treatment outcome is examined. In addition, studies relevant to possible neurotoxic effects of DUP were reviewed.
Results The research is entirely of a correlational nature and, therefore, firm conclusions regarding causation are not possible. There is, however, substantial evidence of DUP being an independent predictor of treatment outcome, particularly remission of positive symptoms, over the first year or so of treatment. Findings regarding the possible neurotoxic effects of DUP are inconsistent.
Conclusions There continues to be evidence consistent with DUP influencing aspects of treatment outcome. Non-correlational studies, such as quasi-experimental designs, could provide stronger evidence regarding causality.
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INTRODUCTION |
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Estimating DUP is challenging given potential difficulties in dating onset of psychosis; establishing criteria for the initiation of effective treatment; the often intermittent or episodic nature of active psychosis; problems of retrospective reports; and discrepancies that can occur between patients and family or close associates in the observation of varying types of symptoms (Norman & Malla, 2001). Fortunately, in more recent publications reliability data are often provided (e.g. Browne et al, 2000; Drake et al, 2000; Malla et al, 2002a), but there are still instances in which the methods for assessing DUP are not well described and/or reliability estimates not reported (e.g. Altamura et al, 2001). 1 For current purposes, we report only results of studies in which the measure of DUP attempts to reflect time from initial onset of positive psychotic symptoms to treatment as opposed to the delay from onset of any psychiatric symptoms (often referred to as duration of untreated illness or DUI). These studies were identified primarily from previous reviews (e.g. Norman & Malla, 2001), articles identified from MEDLINE and PSYCINFO related to duration of untreated psychosis as well as reference lists of articles identified using these methods.
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METHOD |
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Several factors might account for inconsistencies in findings between these studies. For instance, the distribution of DUP tends to have a marked positive skew, suggesting the appropriateness of transformations or non-parametric analyses. Three of the four non-significant findings did not do so (Scully et al, 1997; Linszen et al, 1998; Craig et al, 2000); on the other hand, some studies that found a significant relationship do not report using such procedures (e.g. Larsen et al, 2000; Black et al, 2001). Non-significant reports may also be a result of a restricted range of DUP (e.g. Linszen et al, 1998); combining data for patients who may vary widely in the treatment received (Craig et al, 2000) or possible marked difficulties in estimating DUP using very distant historical data (e.g. Scully et al, 1997). One must be cautious in undertaking such post hoc explanations for discrepancies. At this point, however, a majority of relevant studies are reporting significant bivariate relationships between DUP and level of initial recovery from positive symptoms over the first year or so.
Three publications have examined whether DUP is related to likelihood of relapse once remission has been attained. Altamura et al (2001), in a retrospective study, found that patients with apparently short DUP were less likely to have a multi-episode course. Prospective studies by Robinson et al (1999) and Linszen et al (1998) did not find DUP to predict relapse.
Of ten reports (again using independent databases) examining the relationship of DUP to negative symptoms outcomes (Szymanski et al, 1996; Scully et al, 1997; Haas et al, 1998; Linszen et al, 1998; Edwards et al, 1999; Craig et al, 2000; Ho et al, 2000; Larsen et al, 2000; Black et al, 2001; Malla et al, 2002a), four (Scully et al, 1997; Haas et al, 1998; Edwards et al, 1999; Larsen et al, 2000) have shown a significant relationship. The strength of the relationship for DUP and negative symptoms may be somewhat less than that for positive symptoms, with an average correlation in the low 0.20s.
The few reports examining possible relationships between DUP and social functioning during follow-up have yielded inconsistent results (cf. McGorry et al, 1996; Ho et al, 2000; Malla et al, 2001, 2002b).
On the whole, the current evidence suggests there is frequently a bivariate relationship between DUP and time to or level of remission of positive symptoms, although there may be less consistency with respect to DUP predicting level of negative symptoms after treatment and/or likelihood of relapse after remission.
Is there a confound?
It is important to examine whether any relationship that does exist between
DUP and outcome could be explained by other confounding factors which have in
the past been found to predict treatment outcome. With respect to gender,
Loebel et al (1992)
and Larsen et al
(1996) report males having a
longer DUP than females, but five other studies did not find a difference
(Haas et al, 1998;
Browne et al, 2000;
Drake et al, 2000;
Ho et al, 2000;
Black et al, 2001). Ho
et al (2000) found
that longer DUP significantly related to younger age of onset, but six studies
did not (Haas & Sweeney,
1992; Loebel et al,
1992; Larsen et al,
1996; Haas et al,
1998; Black et al,
2001; Kalla et al,
2002). Several studies have reported longer DUP to be associated
with higher levels of at least some aspects of negative or deficit symptoms at
presentation for treatment (Larsen et
al, 1996; Browne et
al, 2000; Black et
al, 2001; Malla et
al, 2002c). Drake et al
(2000) found a relationship
between longer DUP and higher positive but not negative symptoms at
presentation, but others have found no relation of DUP to initial positive
symptoms (e.g. Larsen et al,
1996; Malla et al,
2002a). DUP is not systematically related to substance
use/misuse or adherence to medication
(Drake et al, 2000;
Norman & Malla, 2002). It
is important to note, however, that significant relationships of DUP to
outcome generally remain when such factors as age at onset, gender and
baseline symptoms are entered as predictors (e.g.
McGorry et al, 1996;
Szymanski et al,
1996; Altamura et al,
2001; Harrigan et al,
2003).
Although several studies have found DUP and indices of premorbid adjustment are not significantly correlated (Loebel et al, 1992; Browne et al, 2000; Ho et al, 2000); others have found lower premorbid adjustment to be significantly associated with longer DUP (Verdoux et al, 1998; Malla et al, 2002a). Any index of premorbid adjustment based on the individuals behaviour close to the onset of psychosis may actually reflect the impact of the symptoms, whereas the use of premorbid adjustment indices based on behaviour earlier in life, such as childhood or early adolescence, are less likely to reflect active psychosis. Malla et al (2002a) found that DUP predicted level of positive symptoms at 1 year independently of childhood or early adolescent premorbid adjustment. Larsen et al (2000) entered gender and premorbid adjustment for childhood, early adolescence, late adolescence, or adulthood into a regression equation before DUP and found that only the latter significantly predicted symptoms 1 year after initiation of treatment. In a 10-year follow-up of an epidemiological first-episode cohort, White et al (further details available from S.W.L. on request) found both premorbid adjustment and DUP to be independent predictors of symptomatic and functional outcomes. Verdoux et al (2001) report data suggesting that premorbid adjustment might account for the relationship of DUP to outcome. It should be noted, however, that Verdoux et al used the best level of the Global Assessment of Functioning Scale (GAF) for any month in the year preceding hospitalisation as the index of premorbid adjustment and clearly such an index could reflect the impact of untreated psychosis. These authors tried to address this possibility by excluding from their analysis patients with a DUP longer than 12 months but this has the effect of reducing the potential of DUP to predict by truncating its range.
The interpretation of findings with respect to premorbid adjustment as a possible explanation for any relation between DUP and treatment outcome is potentially complex. Does poor premorbid adjustment lead to worse outcome and also result in longer DUP with the relationship between the latter two variables being spurious? Is the correlation of premorbid adjustment with outcome largely reflecting the influence of untreated psychosis? Are both having independent effects? In a recent report, Harrigan et al (2003) demonstrate that in a large sample of patients with first-episode psychosis, the effects of DUP on several dimensions of outcome are independent of premorbid adjustment prior to the onset of prodromal or psychotic symptoms. In multiple regression equations that included premorbid adjustment, gender, prodrome duration, diagnosis, age at onset and severity of drug use, DUP remained a significant (and relatively important) predictor of 12-month outcome scores on a quality of life scale as well as negative and positive symptoms. Furthermore, Drake et al (2000) and Harrigan et al (2003) have reported comparable doseresponse curves for the effects of DUP on outcome.
Ho et al (2000) have suggested that reports that find a relationship between DUP and outcome may be confounded by diagnosis, particularly the difference between affective psychosis and schizophrenia-spectrum disorders. There are now several reports that find DUP to predict treatment response in samples which do not include patients with affective psychoses (e.g. Larsen et al, 2000; Black et al, 2001; McGorry et al, 2001; Harrigan et al, 2003). It has also been suggested that inclusion of schizophreniform psychosis and other diagnoses with lower duration thresholds than schizophrenia may distort the relationship between DUP and outcome (Ho et al, 2000). The number of individuals with such diagnoses that are present in samples examining DUP is generally quite small (e.g. Larsen et al, 2000; Black et al, 2001; Malla et al, 2002a). Furthermore, such an argument assumes that there is a fundamental difference in the pathophysiology of such diagnoses. The primary characteristic that distinguishes schizophreniform psychosis from schizophrenia is the duration of psychotic symptoms (Zarafe et al, 2000) and so elimination of patients with such a diagnosis would not be consistent with examining the impact of the full range of DUP.
What are likely mediators of any effects of DUP?
The postulate of ongoing neurodegenerative processes in psychosis is
controversial, although there is evidence consistent with there being
neuroanatomical changes associated with the onset of and continuation of
psychotic disorders (e.g. Velakoulis
et al, 2001; Pantelis
et al, 2003). Several publications have found no
relationship between measures of brain morphology and DUP
(Fannon et al, 2000;
Hoff et al, 2000;
Malla et al,
2002d; Ho et
al, 2003). Madsen et al
(1999) report DUP to be
positively associated with extent of frontal sulcal enlargement at first
admission and Keshavan et al
(1998) found DUP to be
inversely related to the volume of the left superior temporal gyrus.
Barnes et al (2000), Hoff et al (2000) and Norman et al (2001) found DUP unrelated to performance on a variety of neurocognitive tests. Amminger et al (2002) reported longer DUP to be related to an index of cognitive deterioration (based on hold v. no hold indices of performance), but Norman (2002) did not find DUP to be related to the same index in other data. In the most recent report relevant to DUP and cognitive functioning, Joyce et al (2002) found DUP unrelated to level of performance on tasks assessing planning, spatial memory or pattern recognition; but did find shorter DUP related to performance on a task requiring shifting attention from one dimension of a stimulus to another which is postulated to particularly reflect prefrontal functioning.
On the whole, the results with reference to structural and neurocognitive functioning and DUP are mixed. Several studies on neurotoxicity in relation to DUP have used small samples, but sample size does not seem to have a clear relationship to the likelihood of significant findings. To the extent that the data provide any evidence of a neurotoxic effect of untreated psychosis, it seems most likely to emerge with reference to frontal or temporal lobe deterioration and frontal cognitive performance. These correspond to the areas implicated in recent longitudinal studies of changes associated with onset of psychosis (e.g. Pantelis et al, 2003).
Any toxic effects of untreated psychosis are not necessarily mediated through the neural domain. Longer periods of untreated illness could lead to disruptions in social support and it is certainly conceivable that DUP might have effects mediated through reduced self-confidence, increased hopelessness or engulfment, or pre-treatment disruption of education or vocation, all of which could have an impact on treatment outcome.
Other sources of evidence
Definitive evidence of a causal relationship between DUP and clinical
outcome could only come from a randomised control trial comparing earlier and
later detection and treatment. Although using such a design would be
challenging, McGorry (2000)
argues that it might be feasible under some circumstances. An alternative is
the use of quasi-experimental designs comparing treatment results for
geographical regions in which differences have been introduced in
infrastructure for early detection and treatment and/or historical control
design that contrast outcomes for patients before and after such system
changes. Up to this point, the most noteworthy study of this sort is probably
the TIPS trial (Johannessen et
al, 2001) in which geographical regions were
pseudo-randomised to receive an intensive public education campaign plus an
early detection service or conventional care. Preliminary reports suggest that
both DUP and clinical severity at presentation for treatment have been
significantly reduced in the experimental district. No outcome data have yet
been reported and interpretation of findings may be challenging
(McGorry, 2000;
Larsen et al, 2001).
It is particularly important to guard against the possibility that
interventions designed to reduce DUP do not improve outcome primarily through
increased detection of cases that naturally have a more benign course.
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DISCUSSION |
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Certainly, DUP is not the only influence on treatment outcome. As McGorry (2000) suggests, the early intervention field must maintain a balance between enthusiasm and sound research evidence, avoiding unjustified zealotry or scepticism. A balance must also be maintained between a focus on intervening early and intervening well (Carbone et al, 1999; Malla & Norman, 2001). A major legacy of the early intervention movement is increased optimism and enthusiasm concerning the treatment of psychotic disorders. These must be channelled not only into providing earlier treatment, but also into developing and evaluating interventions that better meet the needs of patients and families.
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Clinical Implications and Limitations |
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LIMITATIONS
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