Background: Association between poor cognition and symptom clusters including depressive ideation (eg, guilt) and vegetative symptoms in the absence of dysphoria (nondysphoric depression [NDD]) has been suggested in the elderly. The current study examined associations between NDD and premorbid and concurrent cognitive functioning in younger adults at high risk for psychopathology. Nondysphoric depression and depressed subjects were expected to show poorer premorbid and current cognition than nondepressed participants.
Method: Subjects were adoptees enrolled in the Iowa Adoption Study [Yates W, Cadoret R, Troughton E. The Iowa adoption studies: methods and results. On the way to individuality: methodological issues in behavioral genetics. In: LaBuda M, Grigorenko E, (Eds), Editor. 1999, Commack (NY): Nova Science Publishers, Inc. p. 95-121]. Nondysphoric depression subjects were compared with nondepressed comparison subjects and with subjects with dysphoric depression (DD) on measures of premorbid cognition (estimated by standardized school achievement test scores) and concurrent cognition (intelligence, attention, memory, and executive abilities).
Results: Nondysphoric depression and DD showed lower premorbid cognition and executive functioning, whereas DD showed lower verbal and performance IQ compared to nondepressed subjects. The size of the comparison between NDD and nondepressed subjects for premorbid cognition was double that between DD and nondepressed subjects. No significant differences in cognition were found between NDD and DD. These effects were no longer significant after controlling for premorbid cognition.
Conclusions: Poorer premorbid cognition and executive functions in NDD (and the absence of current cognitive differences compared with DD) suggest that NDD may be a condition of clinical interest. Because poor cognition is a known correlate of alexithymia, these results (including their magnitude) are consistent with the view that NDD may be a paradoxical presentation of depression in persons with limited ability to be aware and to verbally-report emotions.
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