Dimensions of delusions in major depression: Socio-demographic and clinical correlates in an unipolar-bipolar sample

Objective: The present study aims at exploring associations between a continuous measure of distorted thought contents and a set of demographic and clinical features in a sample of unipolar/bipolar depressed patients. Methods: Our sample included 1,833 depressed subjects. Severity of mood symptoms was assessed by the 21 items Hamilton Depression Rating Scale (HAM-D). The continuous outcome measure was represented by a delusion (DEL) factor, extracted from HAM-D items and including items: 2 ("Feelings of guilt"), 15 (" Hypochondriasis"), and 20 ("Paranoid symptoms"). Each socio-demographic and clinical variable was tested by a generalized linear model test, having depressive severity (HAM-D score-DEL score) as the covariate. Results: A family history of major depressive disorder (MDD; p=0.0006), a diagnosis of bipolar disorder, type I (p=0.0003), a comorbid general anxiety disorder (p<.0001), and a higher number of manic episodes during lifetime (p<.0001), were all associated to higher DEL scores. Conversely, an older age at onset (p<.0001) and a longer duration of hospitalization for depression over lifetime (p=0.0003) had a negative impact over DEL scores. On secondary analyses, only the presence of psychotic features (p<.0001) and depressive severity (p<.0001) were found to be independently associated to higher DEL scores. Conclusion: The retrospective design and a non validated continuous measure for distorted thought contents were the main limitations of our study. Excluding the presence of psychotic features and depressive severity, no socio-demographic or clinical variable was found to be associated to our continuous measure of distorted thinking in depression.