Tool teases out mood trait in schizophrenia
medwireNews: Researchers have developed an instrument to distinguish between state and trait depression in patients with schizophrenia.
"Trait depression may be an important and thus far largely neglected feature of schizophrenia," say lead researcher Joshua Chiappelli (University of Maryland School of Medicine, Baltimore, USA) and colleagues.
Notably, they found that trait depression could distinguish between schizophrenia and schizoaffective disorder, whereas state depression could not.
The team's instrument - the Maryland Trait and State Depression (MTSD) scale - contains 36 items, which users rate on a 5-point scale. These are divided into two sections: one relating to trait and one to state depression. The researchers worded the questions to minimize the possibility of currently depressed participants overrating trait depression, and also had the participants (98 patients; 115 controls) complete the scale in a clinical interview environment.
As reported in Schizophrenia Bulletin, factor analysis of the MTSD results for all participants confirmed that the scale successfully separated state and trait depression. Moreover, the results correlated with those of validated measures of state depression (Brief Psychiatric Rating Scale and Profile of Mood States depression subscales).
The patient group comprised 81 with schizophrenia and 17 with schizoaffective disorder. Patients with schizoaffective disorder had higher scores than schizophrenia patients, significantly so for trait depression, in line with the chronic mood symptoms often seen in schizoaffective disorder.
Negative symptoms on the Brief Negative Symptom Scale did not correlate with either state or trait depression. Previous studies showed only that negative symptoms do not relate to current depression, so the current findings "provide additional evidence that negative symptoms are distinct from depression experienced by patients with schizophrenia," comment Chiappelli et al.
By contrast, state and trait depression in control participants strongly correlated with negative symptoms.
"This likely reflects the superficial similarity between these 2 symptom domains and indicates that attempts to measure negative symptoms in a nonpsychotic sample will likely be confounded by depression," say the researchers.
"However, in the schizophrenia sample, these factors were not correlated, suggesting that depression and negative symptoms are distinct clinical phenomena in individuals suffering from schizophrenia."
medwireNews (www.medwirenews.com) is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013
By Eleanor McDermid, Senior medwireNews Reporter