Difficulty concentrating is a common symptom of depression. At times when my depression is most severe, I can't watch a movie or even an hour-long television show, because I just can't focus that long. Half-hour sit coms, maybe, but then you don't really have to pay much attention to those in order to get the humor. I can't read books when my depression is most severe, either, because by the time I get to the end of a chapter, I've already forgotten what happened at the beginning of the chapter.
Post-traumatic stress disorder can make concentration difficult, too. There is the hypervigilence, startling at the smallest sound, things most people would just tune out. There are the intrusive thoughts and memories. Of course, sleep deprivation makes it hard to concentrate, too, and I am always sleep deprived.
I am on Social Security disability but I also supplement my disability check by doing some work as a freelance writer. I get paid by the article, not by the hour. No one would pay me by the hour to write because it takes me much longer than it would take most people to complete a 500-word article. Most of the articles I do are about 500 words and I should be able to complete one in about an hour. On a good day, a really good day, I can do that. But I hardly ever have really good days.
Most days, I am really lucky to get two articles done. Often I can complete one in an entire day. Some days I can't even finish one. See, you have to be able to concentrate to get an article done, especially to get one done in an hour. And I don't concentrate well at all.
It frustrates me sometimes. Mostly I'm used to it and I've adapted to it and I can deal with it since I work from home and usually don't have strict deadlines... but sometimes it frustrates me.
Unfortunately, there isn't much Isaac can do to help me with my lack of concentration. Sometimes it makes it worse, because sometimes he wants to play when I want to work or needs to go out to pee when I am in the middle of writing something. He's good company, though, and I'm willing to put up with him interrupting me sometimes. Too bad there's not a task he can learn to do to help me focus, though.