Possible neurophysiological markers for the differential diagnosis of bipolar and unipolar affective disorders

Background. Despite the completion of the phenomenological stage in the development of psychiatry, tangibledifficulties in the early differential diagnosis of bipolar and unipolar affective disorders remain. In complex differential diagnostic cases, objective research methods can come to the aid of clinicians, among which a special place isgiven to functional neuroimaging methods based on a quantitative assessment of electroencephalograms. Objective:to identify neurophysiological criteria that make it possible to distinguish between groups of patients with bipolar andunipolar affective disorders, to explain the functional meaning of the found patterns and to correlate the data obtainedwith specific clinical variables. Material and Methods. We examined 69 patients aged 20-55 years who were admitted for treatment with a diagnosis of ICD-10: mood disorders (affective disorders - F30-F39): affective disorder within the framework of bipolar disorder or within the framework of a single depressive episode, recurrent depressivedisorder. All patients underwent recording and evaluation of electroencephalogram parameters with calculation ofspectral power and coherence indices for alpha, beta and theta rhythms. Results. An analysis of the data obtainedshowed that patients with bipolar disorder have statistically significantly higher indicators of the spectral power of thealpha rhythm in the occipital (p=0.02), right temporal (p=0.028) leads and beta rhythm in the occipital loci.(p=0.019), as well as interhemispheric coherence of the beta rhythm in the frontal leads (p=0.044) compared withpatients with unipolar affective disorder. Direct correlations were found between the spectral power of the betarhythm and the severity of depressive symptoms, assessed by the Hamilton scale (rs=0.394; p=0.013), in patients withunipolar depression, while in patients with bipolar disorder, inverse correlations were found (rs=-0.467; p=0.037).Coherence indicators of the beta rhythm in the frontal cortex directly correlated with the level of anhedonia (rs=0.389;p=0.016) in patients with unipolar depression.