A number of studies have pointed to a link between depression and type 2 diabetes, but a new study indicates that this is not as straightforward as it seemed. The large Canadian study involving 2,525 adults aged 40-69 has found that it is not depression alone that increases the risk of developing diabetes, but depression in conjunction with metabolic risk factors such as obesity, high blood pressure and unhealthy cholesterol levels,.
The study found that those with metabolic symptoms but not depression were around four times more likely to develop diabetes than normally healthy people, while those with both depression and metabolic risk factors were more than six times more likely to develop diabetes. The combined effect of depression and metabolic symptoms was greater than the sum of the individual effects. But those with depression alone had no more risk than normally healthy people.
There are probably two main causes for this effect. One is that, as evidence shows, people suffering from depression are less likely to adhere to medical advice aimed at tackling metabolic symptoms. This makes the metabolic symptoms worse, which can exacerbate the symptoms of depression, and so it goes, in a horrible negative cycle.
The second reason is that some forms of depression are associated with changes in the body's metabolic systems which can lead to weight gain, high blood pressure and problems with glucose metabolism. Some antidepressant medications can also cause weight gain.
Schmitz, N., Deschenes, S. S., Burns, R. J., Smith, K. J., Lesage, A., Strychar, I., … Wang, J. L. (2016). Depression and risk of type 2 diabetes: the potential role of metabolic factors. Mol Psychiatry. Retrieved from http://dx.doi.org/10.1038/mp.2016.7