Previous reports had linked depression to thyroid function. However, the relationship between thyroid function and clinical characteristics in major depressive disorder (MDD) patients with suicidal attempts (SA) is still unclear.

This study aims to reveal the association between thyroid autoimmunity and clinical characteristics in depressed patients with SA.

We divided 1718 first-episode and drug-naive MDD patients into groups with suicide attempt (MDD-SA) and without suicide attempt (MDD-NSA). Hamilton Depression Rating Scale (HAMD), Hamilton Anxiety Rating Scale (HAMA), and the positive subscale of the Positive and Negative Syndrome Scale (PANSS) were assessed; thyroid function and autoantibodies were detected.

The total scores of HAMD, HAMA and psychotic positive symptoms were significantly higher in patients with MDD-SA, accompanied by higher levels of TSH, TG-Ab and TPO-Ab, than in patients with MDD-NSA, without gender differences. Total scores of positive symptoms (TSPS) in MDD-SA patients with increased TSH or TG-Ab was significantly higher than in MDD-NSA patients and in MDD-SA patients with normal TSH and TG-Ab. The proportion of elevated-TSPS in MDD-SA patients was >4 times that in MDD-NSA patients. The proportion of MDD-SA patients with elevated-TSPS was >3 times that with not-elevated TSPS patients.

Thyroid autoimmune abnormalities and psychotic positive symptoms may be the clinical features of MDD-SA patients. Psychiatrists should be more alert to the possibility of suicidal behaviors when they first encounter such a patient.