For instance, the comorbidity of diabetes mellitus and depression can be revisited by looking to molecular signaling cross-overs between the CNS (relative hypofunction of noradrenaline, dopamine and serotonin compared to acetylcholine, glutamate, and GABA in depression) and the physiological control of beta and alpha cells in pancreas physiology by these neurotransmitters and also the effects of insulin in the brain, etc. (99). Here, INS is linked to depressive disorder.