Higher soft drink consumption may be associated with both a diagnosis of major depressive disorder and greater symptom severity, with the associations observed in women but not in men, according to a multicenter German cohort study.
Among women, greater soft drink intake was tied to a higher likelihood of receiving a major depressive disorder (MDD) diagnosis and reporting more severe depressive symptoms; whereas among men, no statistically significant associations were observed. Investigators also reported that soft drink intake in women was associated with an increased abundance of the gut bacterium Eggerthella, which mediated approximately 3.82% of the total effect of soft drink consumption on MDD diagnosis and 5% of the effect on symptom severity. Microbial diversity decreased with higher intake, although diversity itself wasn't linked to depression outcomes. The associations among women remained after adjusting for body mass index.
“[I]n complex systems, the importance of a mediator cannot be judged by effect size alone, but must be assessed in terms of system function, interaction structure, and dynamic potential,” said lead study author Sharmili Edwin Thanarajah, MD, of the Department of Psychiatry, Psychotherapy and Psychosomatics at the University Hospital Frankfurt at Goethe University Frankfurt, and colleagues.
The investigators analyzed data from the Marburg-Münster Affective Cohort in Germany. Between 2014 and 2018, the cohort enrolled 405 patients with MDD and 527 healthy controls aged 18 to 65 years. Dietary intake was self-reported, psychiatric diagnoses were based on structured clinical interviews, depressive symptoms were measured with the Beck Depression Inventory, and gut microbiome composition was assessed using 16S rRNA sequencing. Statistical models adjusted for recruitment site and education; microbiome models also accounted for sequencing library size. Additional analyses excluding patients with eating disorders and adjusting for total calorie intake confirmed the main findings.
The ivnestigators noted several limitations. Because the design was cross-sectional, causality couldn't be established. Reverse or bidirectional associations remain possible, since patients with depression may consume more soft drinks. Dietary data relied on recall, and the study didn't differentiate between sugar-sweetened and artificially sweetened soft drinks. The mediation analysis also depended on assumptions that cannot be fully tested.
Full disclosures can be found in the published study.
Source: JAMA Psychiatry
