Working memory impairment as a common component in recurrent depressive disorder and certain somatic diseases

Deterioration of the working memory is regarded as one of the most important deficits in a number of somatic diseases. The purpose of the present study was to compare the effectiveness of working memory in 4 groups of patients: 1) diagnosed with recurrent depressive disorder (rDD), 2) with diabetes type 1 (DM1), 3) with diabetes type 2 (DM2), 4) with arterial hypertension (HA) and in healthy controls (HC).

The study comprised 300 subjects: rDD (n=99), DM1 (n=31), DM2 (n=31), HA (n=30) and HC (n=109).Cognitive function assessment was based on Trail Making Test (TMT) and the Stroop test.

Analysis of variance (ANOVA) indicated statistically significant differences of the mean values among particular groups for each of the analysed results of the Stroop Test and TMT (p<0.0001). Patients with DM1 performed better in both TMT and Stroop tests, when compared to those diagnosed with HA. Patients with HA obtained better results than patients with DM2. Patients with rDD performed significantly worse than those with DM1 in both parts of TMT (A/time: p=0.022, B/time: p<0.001) and in the Stroop test (RCNb/time: p<0.001; NCWd/time: p=0.001; NCWd/errors: p=0.443). They also obtained worse results than patients with DM2 and HA, however, the differences were not statistically significant.

1) Our study has confirmed previous results showing association between depressive disorder and cognitive impairment. 2) Patients with rDD had worse performance on working memory tasks than the patients with DM type 1, DM type 2 and HA. 3) Further investigation is needed to clarify the role of inflammatory and oxidative and nitrosative stress (O&NS) processes in neurocognitive dysfunctions occurring in recurrent depression and somatic disease.