Short-term outcome of first episode delusional disorder in an early intervention population
Introduction
The validity of delusional disorder as a diagnostic entity separate from schizophrenia continues to be debated (Hui et al., 2015; Marneros et al., 2012). Winokur initially refined the description of Kraeplin's ‘paranoia’ to describe ‘delusional disorder’ (Winokur, 1977), and in current diagnostic classifications it occurs as delusional disorder in DSM-V and persistent delusional disorder in ICD-10. Delusional disorder has an estimated prevalence of around 0.18% in the general population and between 1 and 4% of psychiatric inpatient admissions (Kendler, 1982; Perala et al., 2007), although the true prevalence is likely to be higher as lack of insight prevents help seeking and recognition of the illness (Perala et al., 2007).
Despite this, delusional disorder is widely assumed to have favourable functional outcomes when compared to schizophrenia, despite ongoing delusional symptoms which can be resistant to treatment (Marneros et al., 2012; Opjordsmoen, 1988). This often leads to different treatment pathways within psychiatric services, such as differential prescribing of antipsychotic medication (Marneros et al., 2012) and service provision (Drake et al., 2000), while noncompliance and disengagement with services has a detrimental impact on treatment outcomes (Munro and Mok, 1995). This is further compounded by the limited high-quality evidence for the effectiveness of treatments for delusional disorder (Gonzalez-Rodriguez et al., 2016; Manschreck and Khan, 2006; Skelton et al., 2015).
However, outcomes in delusional disorder have not been extensively investigated in a first episode population where differences in symptomatology and functioning have been more difficult to illicit (Hui et al., 2015). Extant follow-up studies have either been limited by small samples or not considered other possible confounders in the relationship between diagnosis and outcome. However, the diagnosis of delusional disorder does appear to have some stability (Fusar-Poli et al., 2016; Kulkarni et al., 2016; Marneros et al., 2012) although others continue to question the distinction between delusional disorder and paranoid schizophrenia (Hui et al., 2015).
The National Eden Study is a database of over 1000 patients admitted to Early Intervention (EI) services in the UK and provides an excellent opportunity to investigate the outcome of first episode psychotic disorders in a larger sample with the ability to adjust for a number of potential confounders in the relationship between diagnosis and outcome. This study aimed to investigate 6 and 12-month functional and symptomatic outcomes of first episode psychosis patients who present with a delusional disorder compared to those presenting with schizophrenia, in order to test the hypothesis that a diagnosis of delusional disorder leads to improved functional outcomes.
Section snippets
Setting
The current study was designed as a nested case-control within the National EDEN database. The National EDEN study is a longitudinal cohort study including 1027 first episode psychosis cases admitted to Early Intervention (EI) services between August 2005 and April 2009 from five geographical sites across England: Birmingham, Cornwall, Cambridge, Norwich and Lancashire (Birchwood et al., 2014). It aimed to evaluate the implementation and outcomes of EI services across England. Ethical approval
Sample information
Of the 815 patients with diagnostic information, a total of 48 patients with a diagnosis of delusional disorder and 262 patients with a diagnosis of schizophrenia according to DSM IV were included in this study. However, the number of patients that provided information for each assessment varied, and the specific numbers of participants in each analysis are shown in Table 1, Table 2, Table 3.
Baseline demographics
There were no differences in age of onset, gender or ethnicity between patients with delusional disorder
Summary and interpretation of the results
This nested case control study used data from The National EDEN cohort to compare patients with a diagnosis of delusional disorder to those with schizophrenia and assess differences in outcomes at 6 and 12 months. This is the first study that the authors are aware of to compare outcomes of first episode delusional disorder and schizophrenia patients in a longitudinal follow up study.
This study found that patients with a diagnosis of delusional disorder have better functioning and less severe
Contributors
MB was the CI and grant holder. MB, LE, PJ, DF, TA, NF, VS, SS and MM contributed to the study design and execution. The data were analysed by TR and AT, and TR with AT drafted the manuscript, and all authors reviewed the manuscript. MB acts as guarantor. The University of Birmingham (UK) acted as the study sponsor.
Funding
This work was supported by grants from the UK Department of Health (RDD/ARF2) and the National Institute of Health Research (NIHR) under the Programme Grants for Applied Research Programme (RP-PG-0109-10074). The views expressed in this publication are those of the authors and not necessarily those of the NHS, NIHR or the Department of Health. Professors Birchwood and Singh are part funded by the National Institute for Health Research (NIHR) through the Collaborations for Leadership in Applied
Conflict of interests
None to declare.
Acknowledgements
We thank the UK Mental Health Research Network for their support and assistance and all National EDEN participants.
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