Comparative study of electroencephalographic findings in patients with depression and schizophrenia

Introduction: Schizophrenia and depression are two major and very common mentaldisorders worldwide. Many clinical questionnaire and scales have been formulated todiagnose these cases. Standard (qualitative) electroencephalography (EEG) has alsobeen routinely employed in the diagnostic evaluation of patients of these disorders.However quantitative EEG (qEEG) has not been frequently used in evaluation of thesedisorders. Qualitative EEG (qEEG) findings differ between patients with schizophreniaand patients with depression, but results are not consistent. We performed this study todetermine the differences in EEG parameters(qualitative and quantitative) betweenpatients with schizophrenia, patients with depression, and healthy subjects.Materials and Methods: Our study included 69 patients with schizophrenia, 69patients with depression, and 138 healthy subjects. All patients and healthy subjectswere aged between 18-50 years. All clinical diagnoses were made according to DSM-IVdiagnostic criteria. Standard EEG was performed on all study participants and artefact-free 100-second epochs were selected from the recorded material and analysed withFast Fourier Transformation (FFT) analysis.Observations and Result: Of the entire sample of patients, 40.58% had abnormal EEG.Patients with schizophrenia when compared with healthy subjects showed increaseddelta, theta, and beta activity and decreased alpha activity. Patients with depression alsoshowed similar results, but in fewer regions. In patients with schizo-phrenia, deltapower over some frontal regions was increased in comparison with those in patientswith depression. Schizophrenic patients and healthy subjects showed interhemisphericasymmetry, but it was absent in patients with depression.Conclusion: Abnormal EEG findings in patients with schizophrenia and depression isnot very common. However, on qEEG, the patients with schizophrenia had in-creaseddelta power in comparison to patients with depression. Hence, qEEG may have a rolein clinical differentiation between these two mental disorders and it may be especiallyimportant in cases of negative-symptom schizophrenia.Key words: Schizophrenia, Depression, quantitative electroencephalography(qEEG).