Comorbidities linked to treatment-resistant depression in older adults with MDD

Older adults with late-onset major depressive disorder and anxiety or substance use disorders were more likely to experience treatment-resistant depression, a study published in the Journal of Clinical Psychiatry showed.

“The prevalence rate of depression peaks in old age. It is estimated that 2% to 5% of community-dwelling adults [aged]65 years and older meet the diagnostic criteria of major depressive disorder,” Po-Chun Lin, MD, of the department of psychiatry at Tri-Service General Hospital, National Defense Medical Center in Taipei, Taiwan, and colleagues wrote.

Lin and colleagues sought to determine the association of treatment resistance with physical and psychiatric comorbidities in older adults diagnosed with MDD.

The population-based cohort study included 27,189 eligible participants, who were aged 65 years or older and diagnosed with first-episode MDD, taken from the Taiwan National Health Insurance Database between Jan. 1, 2001, and Dec. 31, 2010. One year follow-up was assessed for incidence of resistance to treatment, defined as failure to respond to at least 2 antidepressants, with treatment-resistant tendency (TRT) defined as unresponsiveness to the first antidepressant. The Charlson Comorbidity Index was utilized to determine physical comorbidities.

Results among all participants showed that 16.6% were diagnosed with anxiety disorders, 1.5% with alcohol use disorders and 1.6% with a substance use disorder. Approximately 16.6% of patients registered a CCI score of zero regarding physical comorbidities. After the 1-year follow-up interval, 22.1% of patients met TRT criteria, with 1.6% eventually developing TRD.

Anxiety disorders (OR, 2.06; 95% CI, 1.67–2.53), substance use disorders (OR, 2.11; 95% CI, 1.26–3.53), and higher CCI scores (OR, 1.06; 95% CI, 1.01–1.10) carried significant associations with TRD. Anxiety disorders (OR, 1.44; 95% CI, 1.34–1.55) and higher CCI scores (OR, 1.06; 95% CI, 1.05–1.08) were also significantly associated with TRT.

“Our findings may serve as a reminder to clinicians to be aware of possible psychiatric comorbidities, particularly anxiety and substance use disorders, when reporting poor treatment response to antidepressants in elderly patients with late-onset MDD during the first year of treatment,” Lin and colleagues wrote.