Individuals with internalizing disorders have increased mortality risk

Individuals with internalizing mental disorders had a significantly higher mortality rate compared with those without these disorders.

This discovery highlights the utility of using a transdiagnostic internalizing factor when predicting mortality risk, according to Hyunsik Kim, PhD, assistant professor in the department of psychology at Sogang University in South Korea, and colleagues.

“The significant interaction between internalizing and physical health indicates that the former dimension is more likely to have an effect on early death for currently physically healthy individuals,” Kim and colleagues wrote.

The researchers examined the usefulness of a transdiagnostic internalizing factor over disorder-specific variance, the factor’s ability to predict mortality risk and the impact of self-reported physical health on internalization and early mortality. They analyzed data from 6,329 participants recruited through the Midlife in the United States study. Participants completed a phone interview and self-administered questionnaire, and the researchers followed the cohort until October 31, 2015 or death. They measured symptoms scores for major depressive disorder (MDD), generalized anxiety disorder (GAD) and panic disorder symptoms and assessed neuroticism.

Participants’ mean age was 46.77 years; 88.04% of participants identified as white and 52.64% were women. During the study period, 1,234 participants died, with a mean survival time of 11.5 years. However, the mean survival time for the entire study cohort was 19.23 years. Kim and colleagues found MDD, GAD and neuroticism significantly predictive of morality risk using hierarchical regression models. With Cox regression analysis, the internalizing factor significantly and positively predicted mortality risk after adjustments (HR = 1.12, 95% CI: 1.05-1.16, P < .01). However, when their shared variance in internalizing was accounted for, the degrees to which MDD, GAD and neuroticism predicted mortality risk were attenuated, respectively, by 67.2%, 86.9% and 87.1%, according to the researchers. Internalizing significantly predicted mortality risk among participants who self-reported excellent health, which was not consistent among those who reported poorer physical health. Analysis on the internalizing factor level revealed a 12.3% increase in mortality rate for every 1-standard deviation unit increment. Disorder-specific variances had no significant impact on predicting mortality risk. However, internalizing accounted for 34.93% of MDD, 24.21% of GAD, 25.81% of panic disorder and 23.91% of neuroticism variance.

Kim and colleagues speculated the higher mortality rate among individuals who internalize can possibly be explained by maladaptive coping, physical inactivity or a greater likelihood of experiencing adverse life outcomes.

“These findings highlight the clinical utility of using the transdiagnostic internalizing factor for prediction of an important future outcome and support the argument that internalizing psychopathology can be a meaningful liability to incorporate into intervention and prevention research, and to explore in public health practice,” they wrote.