Psychotic Depression - A Valid Psychiatric Syndrome?

Date: Jul-17-2012The number of studies reporting significant and clinically relevant differences between psychotic depression (PD) and non-PD has increased considerably over the past decades. This summary of the current evidence suggests that psychotic depression now fulfills the criteria for a valid psychiatric syndrome.

The suggested redefinition of psychotic depression in the ICD-11 is merited, and such a revision will be of benefit to both research and clinical practice.
Psychotic Depression - Delusional Depression
Danish researchers have collected new data that support a new classification of psychotic depression (PD), i.e. depression that is accompanied by psychotic symptoms, also referred to as delusional depression in the DSM-IV.

Based on finding various clinical, therapeutic and prognostic differences between PD and non-psychotic depression (non-PD), it was proposed that PD should be re-classified as a class of depression in its own right.
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The paper, published in the current issue of Psychotherapy and Psychosomatics, deals with issues for and against classifying PD as a distinct syndrome under affective disorders. Based on the current evidence, the researchers will present an outline for redefining PD at the 2015 11th revision of the International Classification of Disease (ICD-11).

Patients with psychotic depression suffer from delusions and/or hallucinations, in addition to their depression. It is not an uncommon disorder that is under-diagnosed, under-treated and has a high morbidity and mortality. In comparison with other, less prevalent and less severe mental disorders, psychotic depression has been somewhat neglected in terms of its level of attention.

Psychotic depression patients typically display anhedonia (cannot experience pleasure), psychomotor retardation, loss of interest, poor concentration, delusions of guilt, disease, and feelings of impending disaster or worthlessness. Apart from the psychotic features, PD has a distinct symptomatology that sets it apart from non-PD cases, which involves rumination, psychomotor disturbances in the form of agitation or retardation, insomnia, perplexity and cognitive dysfunction.

The course of the disorder is linked to elevated rates of relapse and higher long-term psychosocial impairment, as well as higher mortality rates than non-PD patients, which could be due to the higher suicide risk.

One of the DSM-IV Work Group on Mood Disorders' arguments against classifying PD as a disorder in its own right is that we already have too many psychiatric disorders. However, the argument sounds contradictory, given that PD is a relatively frequent disorder, which is already defined in the diagnostic manuals.

Another counterargument for classing PD as a distinct disorder is the relationship between depression severity and the presence of psychosis based on suggestions that differences between PD and non-PD could reflect just stages of depressive severity.

However, according to evidence in recent studies, episodes of PD are not necessarily 'severe', based on the number of depressive symptoms. In addition, the study showed that patients who had no history of psychosis could experience nonpsychotic depressive episodes with a greater severity in symptoms than psychotic depressive episodes in patients with PD.

PD also has low diagnostic stability, another reason perhaps for not re-classifying it as a separate illness.

Having said this, all mental disorders, and all general diseases for that matter, can be subject to changes in diagnoses over time and so-called diagnostic drifts.

Even though depression can be inherited, schizophrenia and bipolar disorder are situated at the other end of the spectrum amongst the less heritable disorders. Studies have suggested a stronger heritability compared with patients with non-PD - there is a notable link between PD and family history.

The DSM-IV Work Group also counter-argues that PD should not be classed as a disorder in its own right due to its response to treatment. According to general opinion, PD shows a poor response to antidepressant monotherapy, with some evidence even suggesting that this treatment can worsen psychotic symptoms.

According to recent studies, the best treatment for PD involves prescribing antidepressant alongside antipsychotic medications. In support of these results, the majority of PD expert guidelines therefore recommend that a first line treatment for these patients should either consist of electroconvulsive therapy, or a combination of an antidepressant and an antipsychotic as first-line treatment.

This treatment recommendation is substantially different to that of non-PD patients, where the broader use of antipsychotics is only considered if the patient did not respond to at least two courses of antidepressant monotherapy.

The risk of developing bipolar disorder is particularly high in those who suffer from unipolar psychotic depression (UPD), with relatives of UPD patients being more frequently diagnosed as being bipolar than relatives of non-PD patients. Unipolar depressed relatives of patients with bipolar disorders have a higher risk of developing the psychotic subtype, compared with unipolar depressed relatives of healthy controls.

Similar to the case of UPD, it seems that the psychotic subtype of bipolar depression may also affect symptomatology, treatment response, course of illness and prognosis. Because of distinct various factors, such as clinical presentation, neurobiology, heritability, prognosis and treatment response, PD fits the criteria as a valid psychiatric syndrome.

The researchers conclude staying that they believe that the suggested redefinition of PD in the ICD-11 is merited, and the revision will benefit both research and clinical practice, as the suggested classification permits PD to be defined as a useful 'meta-syndrome' called 'psychotic depression' in the DSM-IV

chapter of affective disorders.
Written by Grace Rattue

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