Latent Toxoplasmosis is Associated with Depression and Suicidal Behavior

Abstract

Objective

Neuroinflammation is implicated in the pathophysiology of depression. Toxoplasma gondii (T. gondii) causes chronic brain inflammatory process and may thus contribute to both depression and its most serious complication, suicidal behavior. In this study, we hypothesized that latent toxoplasmosis may underlie current depression and/or suicidal behavior.

Method

Currently depressed individuals (N = 384) and age, sex, and residence-matched healthy controls (HC) (N = 400) were tested for latent toxoplasmosis (i.e., positive serum T. gondii IgG antibodies). Exclusions included positive IgM and negative IgG antibodies indicating acute T. gondii infection and history of cognitive problems. Depression severity and history of lifetime suicide attempts were assessed using Beck Depression Inventory (BDI) and Columbia Suicide Severity Rating Scale, respectively.

Results

Participants with seropositive anti-T. gondii IgG antibody had a significantly higher odds of being depressed compared with seronegative participants (OR = 2.9, 95% CI: 1.9–4.3; p < 0.001). BDI score was significantly different between depressed seropositive and depressed seronegative individuals (IgG＋: mean (SD)= 39.65 (11.83) vs. IgG−: mean (SD)= 33.44(9.80); t = 5.03, p < 0.001). Further, seropositive depressed participants were more likely to have prior history of actual suicide attempts compared with seronegative participants (OR= 6.2, 95% CI: 3.4–11.2, p < 0.001).

Conclusions

Latent toxoplasmosis may represent be a risk factor for depression and suicidal behavior. Screening for, and treatment of, underlying T. gondii infection may help improve depression and curb the increasing suicide rates. Future studies should prospectively test these hypotheses to be adequately implemented.

HIGHLIGHTS

• Latent toxoplasmosis has been linked to history of psychiatric disorders.

• Depressed individuals have higher positivity rate of T. gondii IgG antibody than healthy controls.

• Depressed T. gondii seropositive individuals have increased likelihood to have history of suicidal behavior.

Keywords:

• Depression
• latent toxoplasmosis
• suicidal behavior

ACKNOWLEDGMENTS

We thank the study participants for their time and effort.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the author(s).

AUTHOR CONTRIBUTION

Ahmed M. Kamal, Amany M. Kamal and Aliaa S. Abd El-Fatah designed the study. Ahmed M. Kamal conducted the psychiatric interviews. Amany M. Kamal performed the parasitology procedures. Aliaa S. Abd El-Fatah conducted the medical evaluation. Eptesam E. Hassan performed the statistical analysis. All authors conceptualized, edited and approved the final manuscript.

Additional information

Notes on contributors

Ahmed M. Kamal

Ahmed M. Kamal, MD, PhD, is Associate Professor, Psychiatry Department, Faculty of Medicine, Minia University, Egypt.

Amany M. Kamal

Amany M. Kamal, MD, PhD, is Associate Professor, Parasitology Department, Faculty of Medicine, Minia University, Egypt.

Aliaa S. Abd El-Fatah

Aliaa S. Abd El-Fatah, MD, PhD, is Associate Professor, Internal Medicine Department, Faculty of Medicine, Minia University, Egypt.

Mina M. Rizk

Mina M. Rizk, MD, is the Paul Janssen Postdoctoral Fellow, Department of Psychiatry, Columbia University Irving Medical Center, New York, NY. Eptesam E.

Eptesam E. Hassan

Hassan, MD, PhD, is Associate Professor, Public Health and Preventive Medicine Department, Faculty of Medicine, Minia University, Egypt.