This study examined low episodic memory scores as a potential risk factor for developing depression by using longitudinal data from the PART project in Stockholm, Sweden.

A population-based sample of non-depressed participants (20-64 years) were re-examined three years after the initial screening (n=708). At baseline, a neuropsychological test battery including tests of episodic memory was administered. Also, information about demographic and socioeconomic factors, alcohol use, and anxiety diagnoses was collected. The psychiatric data for depression diagnoses were collected both at baseline and follow-up.

Logistic regressions were conducted on three separate study groups that were defined according to three different assessments of episodic memory (i.e., free + cued recall, free recall or cued recall) among individuals who scored in the 25 lowest or highest percentiles in the memory tests. The results suggest that low episodic memory performance defined as the sum of free and cued recall of organizable words, constitute a risk for depression diagnosis three years later, even after controlling for differences in demographic, socioeconomic, alcohol use and anxiety levels. Also, female gender, low educational level, and financial strain constituted significant risk factors for developing depression.

This study indicates that low episodic memory performance predates depressive diagnosis and might be considered as a premorbid marker of incipient depression.