Our colleagues in the Netherlands have published a systematic review in Endocrinology, Diabetes & Metabolism
This question has been around for a long time, as early as the 1930s. It is not just, is there an association? But also, is it stress and mood that causes extreme glucose fluctuations or could it be the other way around: glucose variability (GV) affecting mood and leading to psychological problems?
Just eight studies out of 2,316 fulfilled the selection criteria, four in type 1 diabetes and four in type 2 diabetes. The papers were published between 1990 and 2018. As continuous glucose monitoring (CGM) has not been around that long, four of the studies used self-monitoring of blood glucose (i.e. with a finger prick: SMBG) to determine GV. Of the remaining four, three used blinded CGM, and one a glucose/insulin infusion procedure. As there are several ways of looking at GV, the authors of the studies used several metrics; including metrics of amplitude such as standard deviation (SD), coefficient of variation (CV) or time such as continuous overall net glycaemic action (CONGA). All studies assessed negative mood (e.g. depressive symptoms) and three studies also measured positive mood (e.g. “happy”). Half of the studies used retrospective questioning (e.g. how the person has been feeling over the past 2 weeks) and some more recent studies used apps to enable questions to be asked ‘in the moment’.
Half of the studies reported an association between GV and mood. Two studies in type 2 diabetes found that a higher rate of postprandial (following a meal) glucose increase was associated with more negative mood symptoms. Two studies in type 1 diabetes reported a possible cumulative effect of multi-day GV on depressive mood. The remaining four studies did not find an association.
The authors concluded that the evidence available today is not very clear. So, we still don’t have an answer to this highly relevant question. The major methodological limitations of the studies included in the review were the use of SMBG in half of the studies, which is not the best way to assess GV. Second, mood was assessed in four studies through retrospective questionnaires. These measures do not allow to capture mood swings during the day at the same time as the glucose reading.
With increased used of CGM and new methods to assess mood in the moment (e.g. ecological momentary assessment), we have better tools now to explore this question. So, hopefully, more research will be conducted and published in the near future.
Muijs LT, Racca C, de Wit M, et al. Glucose variability and mood in adults with diabetes: A systematic review. Endocrinol Diab Metab. 2020;00:e00152. https://doi.org/10.1002/edm2.152