The comprehensive treatment of delusional disorder

Dear Editor,

The ethical principles which govern medical practice, in this case psychiatry, underline the need for patients to be treated as comprehensively as possible, as is demanded by the principles of care, dignity, integrity and justice.¹ In spite of the fact that the prevalence of delusional disorder (DD) stands at 0.18% of the population² there are no clinical practice guides (CPG) for DD which guide its treatment, so that the information from the schizophrenia CPG is used instead. This may be due to the fact that its place in psychiatric hospital care has not been clearly defined to date, as it has varied between being considered a schizophrenia subtype,³ an affective disorder⁴ or a separate entity.⁵ It is now defined in the CIE-10⁶ as a psychosis involving persistent delirious ideas, although functioning is relatively well conserved, while there may also be a few other psychotic symptoms such as negative symptoms and minor hallucinations. Nevertheless, recent studies not only contribute to establishing this disorder as a differentiated entity,^7–11 as they also rule out the possibility that it is a monosymptomatic disorder¹² and emphasise the existence of different dimensions of the same, as well as its high comorbidity. Although the delirious symptom is not specific to DD, which therefore justifies its inclusion within the psychotic spectrum,¹³ it has been shown to have certain specific qualities and characteristics which differentiate it from schizophrenia. Thus while DD would display fewer delirious ideas than is the case in schizophrenia, they would be more intense. There would also be certain qualitative differences respecting schizophrenia. The predominance of somatic or jealous delirious ideas would be intrinsic to DD in comparison with those profiles which predominantly display religious delirious ideas that would be characteristic of schizophrenia.⁷ The other dimensions of DD underline not only the role of delirious ideas but also the relevant importance of affective symptoms, especially depression,^8,9,13 cognitive symptoms^9,13,14 or the risk of suicide as a comorbidity.¹⁵ Likewise, poorer awareness of the disease has also been detected, or even a worse response to antipsychotic drugs than is the case in schizophrenia.⁷ All of these factors mean that this disorder has its own peculiarities and profile which make it necessary treat it more widely than the delirious symptom alone or merely to extrapolate from data on schizophrenia treatments.

Pharmacological treatment is currently considered to be standard for the treatment of DD, and antipsychotic drugs are the cornerstone of this. A recent systemic review of descriptive studies which cover 385 DD patient cases treated using drugs¹⁶ has shown these to be effective, as there is a ≥50% improvement over the basal situation in 33.6% of cases, while first generation antipsychotics (FGA) are superior to second generation ones (SGA) (FGA 39% vs SGA 28%; χ² = 5.2595; P ≤ .02; RR: 1.40; IC 95%: 1.04–1.88), while no specific individual antipsychotic is superior any other. More data are required on the latest antipsychotic drugs, given that the majority of the data on SGA refer to Risperidone or Olanzapine, while it would be of interest to determine the role of antipsychotic drugs which have an outstanding mood regulating function, as is the case for Quetiapine, or good tolerability such as Aripiprazol. Antidepressive drugs too may play a promising role in treatment, given the importance of the above-mentioned depressive dimension and other symptoms such as anxiety or irritability, as well as the good overall response to them which has been found. This is better than the response to antipsychotic drugs (response ≥50% in 50% of cases), although the sample size was small. They may be especially useful in the somatic subtype.¹⁶ Patient lack of awareness of the disease and possible lack of adherence also suggest a role for prolonged liberation parenteral drugs as well as the possible role of psychoeducation and psychological therapies aimed at improving the capacity for introspection, awareness of the disease and adherence. Cognitive-behavioural therapy has also been shown to have a moderate effect in improving secondary variables such as the social self-esteem of these patients.¹⁷ It would also be necessary to study the potential of treatments of this type or other psychological treatments such as metacognitive training on the cognitive traits underlying the delirious ideas which characterise DD, or cognitive repair¹⁸ of the cognitive symptoms existing in the disorder. To conclude, we emphasise that given that the intrinsic profile of the disorder is becoming increasingly consolidated, studies and especially clinical trials or large-scale naturalistic studies are necessary to study the treatment of DD as a differentiated entity rather than a schizophrenia sub-group under the heading of “other psychoses”.

Transparency declaration: the main author, José Eduardo Muñoz Negro, declares this manuscript to be an honest, accurate and transparent description of the study presented, that no important aspect of the study or studies described has been omitted, and that differences respecting the study initially planned have been explained (and if they are relevant, registered).^19,20