Stability of the Subtypes of Major Depressive Disorder in Older Adults and the Influence of Mild Cognitive Impairment on the Stability.

OBJECTIVES: To assess 1) the longitudinal stability of the atypical, melancholic, combined atypical-melancholic and the unspecified subtypes of major depressive disorder (MDD) according to the diagnostic and statistical manual of mental disorders (DSM -IV) specifiers in older adults, and 2) the effect of mild cognitive impairment (MCI) on the stability of these subtypes.

DESIGN: Prospective cohort study with a 5.1 year-follow-up.

SETTING: Population-based cohort from Lausanne, Switzerland.

PARTICIPANTS: A total of 1,888 participants (mean age: 61.7 years, women: 69.2%) with at least two psychiatric evaluations, one after the age of 65 years.

MEASUREMENTS: Semistructured diagnostic interview to assess lifetime and 12-month DSM-IV Axis-1 disorders at each investigation and neuro-cognitive tests to identify MCI in participants aged 65 years and over. Associations between lifetime MDD status before and 12-month depression status after the follow-up were assessed using multinomial logistic regression. The effect of MCI on these associations was assessed by testing interactions between MDD subtypes and MCI status.

RESULTS: 1) Associations between depression status before and after the follow-up were observed for atypical (adjusted OR [95% CI] = 7.99 [3.13; 20.44]), combined (5.73 [1.50; 21.90]) and unspecified (2.14 [1.15; 3.98]), but not melancholic MDD (3.36 [0.89; 12.69]). However, there was a certain degree of overlap across the subtypes, particularly between melancholic MDD and the other subtypes. 2) No significant interactions were found between MCI and lifetime MDD subtypes regarding depression status after follow-up.

CONCLUSION: The strong stability of the atypical subtype in particular highlights the need for identifying this subtype in clinical and research settings, given its well-documented links to inflammatory and metabolic markers.