Every year, I am struck by how far we still have to go to learn what is going on in the depressed brain. 7.6 % of US citizens ages 12(1) and up suffer per year, and medications are unable to help at least 1/3 of those afflicted.
Part of the struggle is the sheer complexity of this phenomenon. For example, Duman et al (2015) cited nutrition, sex sterioids, cardiovascular VEGF, stress, and the immune system all effect and are impacted by depression and anxiety.(2) Others have noted how brain activity shifts so the sufferer struggles to remember, make decisions, and feel motivated. The following article adds another component. It describes how the very structures of the brain are changed, possibly minimizing the ability to recall positive memories while more strongly linked to areas associate with punishment.
Of course, these are not taking into account the environmental factors like trauma, social isolation, stressors (like financial, employment, relationship conflict) that also play apart. In all, I never want to forget that a sufferer cannot easily solve this problem. Hence why therapists like myself work with the person, and sometimes a team of people, to rebuild and repair.
2 Synaptic plasticity and depression: new insights from stress and rapid-acting antidepressants, Ronald S Duman, George K Aghajanian, Gerard Sanacora, & John H Krystal. Nature Medicine, 22, 238–249 (2016) doi:10.1038/nm.4050 Received 11 March 2015, Accepted 21 January 2016, Published online 03 March 2016