Individuals with major depressive disorder (MDD) have lower odds of testing seropositive for measles despite previous immunization, according to a study. This suggests that MDD may increase susceptibility to the infection due to impaired maintenance of vaccine-related protection against measles.
“Our findings may have important implications for public health as the high lifetime prevalence of MDD may weaken population levels of immunity to measles (and potentially other infectious diseases) with a subsequent increase in the risk of transmission of measles (and potentially other viruses) within the population,” the authors said.
“It is conceivable that healthcare providers could mitigate this problem by prioritizing depressed populations for antibody screening and revaccination efforts,” they added.
In the study, the authors quantified IgG antibodies to measles in 64 patients with bipolar disorder (BD; mean age 33.2 years), 85 patients with MDD (cMDD; mean age 34.6 years), 82 patients with a history of MDD (rMDD; mean age 32.0 years) and 202 comparison controls without depression (mean age 30.6 years). All participants were born after the introduction of the measles vaccine in the US in 1963.
The rates of seropositivity for measles were lower in the both the cMDD and rMDD groups than in the control group (72.9 percent and 75.6 percent vs 86.6 percent). Logistic regression analysis showed that compared with controls, individuals with current MDD or history of MDD had half the odds of testing seropositive for the infection (cMDD: adjusted odds ratio [OR], 0.47; 95 percent CI, 0.24–0.90; p=0.021; rMDD: adjusted OR, 0.50; 0.26–0.97; p=0.038). [Psychol Med2018;doi:10.1017/S0033291718000661]
On further analysis, within the combined MDD group, medicated patients (n=48) were less likely to show seropositivity relative to those who were unmedicated (n=119; adjusted OR, 0.39; 0.18–0.85; p=0.018).
Results for BD were not significant, with the likelihood of being seropositive similar to controls (p=0.329), patients with current MDD (p=0.355) and those with a history of MDD (p=0.449).
“Taken together, these results support the general hypothesis that depression affects the maintenance of immunity into adulthood following childhood vaccination,” the authors said.
While specific mechanisms underlying the impaired immunogenicity of measles vaccines in individuals with MDD remain unclear, previous data provide evidence that depression may have immunosuppressive effects in some patients. [Brain Behav Immun 2017;66:193-200; Brain Behav Immun 2011;25:221-229; Sleep2012;35:1063-1069]
“Thus, one possible explanation for our results is that individuals who go on to develop MDD have a normal rate of seroconversion following vaccination but lose humoral immunity to measles due to the endocrine and immunological abnormalities that occur in the context of depressive episodes,” the authors pointed out.
The authors, however, acknowledged several limitations to the study, including the absence of immunization records and data on postvaccine antibody titres. Future studies should measure antibodies to viruses, such as rubella and polio, to evaluate whether the MDD-associated reduction in seropositivity to measles reported in the current study is specific to measles or whether it extends to other pathogens.