Comorbid thyroid disease in patients with major depressive disorder - results from the European Group for the Study of Resistant Depression (GSRD).

This multicenter study of the European Group for the Study of Resistant Depression (GSRD) aimed to explore the association between major depressive disorder (MDD) and comorbid thyroid disease. A total number of 1410 patients` characteristics in terms of demographic and clinical information were compared between MDD subjects with and without concurrent thyroid disease using descriptive statistics, analyses of covariance (ANCOVA) and binary logistic regression analyses. We determined a point prevalence rate for comorbid hypothyroidism of 13.2% and 1.6% for comorbid hyperthyroidism respectively. Patients with MDD+comorbid hypothyroidism were significantly older, more likely to be female, inpatient and suffering from other comorbid chronic somatic conditions. Furthermore, MADRS score at onset of the current depressive episode was significantly higher, psychotic features of depression were more likely pronounced. Overall, patients in the MDD+comorbid hypothyroidism group were rather treated with a combination of drugs, for example, pregabalin, antipsychotic drugs and mood stabilizers. In the MDD+comorbid hyperthyroidism group patients were significantly older, of Caucasian origin and diagnosed with other somatic comorbidities. In conclusion, our analyses suggest that abnormal thyroid function, especially hypothyroidism, is linked to depression severity and associated with distinct psychopathologic features of depression. However, comorbid thyroid disease has no influence on treatment response. A combination or augmentation of psychopharmacological drugs, especially with antipsychotics, mood stabilizers and pregabalin is more likely in patients with hypothyroid conditions. Thyroid disorder is frequently found in combination with other chronic somatic diseases including hypertension and heart disease.