When you have a chronic illness, being tired is a little different. Some illnesses can affect attention, ability to focus, and overall motivation. This can then go on to cause mild to even severe depression, as well as anxiety. A lot of these symptoms can overlap. Some symptoms can actually cause the others, and it can be hard to tell what started first, and what is causing what. Brain fog is a very common symptom for people with EDS, even hypermobility or other connective tissue diseases.