Association of Thyroid Function With Suicide Ideation/Attempt -A Systematic Review and Meta-analysis

Background: Thyroid disorders are very prevalent and could affect virtually the entire human body, including cognitive and psychiatric domains. However, the relationship between thyroid dysfunction and suicide is still controversial. Material and Methods: A systematic review and meta-analysis was conducted to describe the association of thyroid function with suicide ideation/attempt in adults. A comprehensive search from databases’ inception (MEDLINE, EMBASE, Cochrane, PsycINFO, PsycArticles, PSYNDEX and Scopus) to July 20, 2018 was conducted with no language restrictions. We included studies that reported mean values and standard deviation (SD) of thyroid hormone levels [Thyroid-stimulant hormone (TSH), free T4 (FT4), free T3 (FT3), total T4 (TT4), and total T3 (TT3)] in patients with suicide ideation/attempt compared with controls. Four reviewers worked independently and in duplicate for assessment of inclusion criteria, data extraction, and assessment of risk of bias. The mean value and SD of the thyroid function tests were used to calculate the mean difference for each subgroup. Random-effects models for meta-analyses were applied. Results: Overall, 2278 articles were identified, and 13 observational studies met the inclusion criteria. These studies involved 2651 participants, including 817 participants diagnosed with suicidal ideation/attempt. Group sizes of patients with suicide ideation/attempt ranged from 7 to 122 participants with mean age ranging from 23 to 49 years. Control group sizes ranged from 8 to 464 participants with mean age ranging from 24 to 50 years. Two studies included only women, two studies included only men, and 9 studies included both (% female range: 29 to 78%). Patients with suicide ideation/attempt had lower levels of FT3 (-0.19 pg/mL; P=0.04) and TT4 (-0.23 µg/dL; P=0.05) compared to controls. There were no differences in TSH, TT3 or FT4 levels between groups. In a subgroup analysis comparing current suicidal ideation vs current suicidal attempt vs history of suicidal ideation/attempt with the control group, there were no differences in any of the thyroid function tests. None of the included studies compared rates of overt/subclinical thyroid disease among groups. The overall risk of bias of the included studies was low-to-moderate. Conclusions: There is scarce evidence regarding the association of thyroid disorders and suicide. We found statistically significant lower thyroid hormone levels in patients with suicidal ideation/attempt. The clinical implications of this finding remain unknown and further research is needed to evaluate the association of thyroid disorders with suicide.