Difficulties with cognition and focus are almost universal in folks with moods. In the scientific literature there have been attempts to distinguish between mood related problems and problems that tend to persist regardless of mood state.
There is probably nothing that can more profoundly affect our brain’s ability to focus than an episode of depression or mania.
These functional brain images (functional meaning that they show brain activity rather than brain structure) show the kind of changes in brain function that can take place with depression. On the right you see normal brain activity and on the left you see brain activity during an episode of depression. Yellow represents normal levels of activity and green and blue represent abnormally low levels of activity. As you can see, depression lowers activity throughout the brain. It is literally like a dimmer switch for the brain.
These changes are much greater than the effects of medications. Most people who
are getting treated with medications tend to assume that it is the medications that are causing cognitive problems. In our clinical experience, in the absence of severe sedation (bumping into things, having trouble staying awake), medications never cause as severe an effect on brain function as a mood episode.
There is also evidence to suggest that the brain effects of a mood episode persist much longer than the mood episode itself. A study of patients hospitalized for a manic episode found that cognitive impairment took up to six months to return to its usual level after mood was back to normal.
If you are noticing trouble thinking clearly and you are feeling either unusually energized or depressed, the change that is most likely to improve this is not reducing medications, it is making sure that you are getting the most effective treatment for your moods.
Bipolar Cognitive Issues
People with bipolar mood swings have three kinds of cognitive problems. Here we are going to talk about two of these – problems that are related to a mood episode (either being manic or energized, or depressed), and problems that tend to persist when the person is not energized or depressed. We are not going to talk about the adverse effects of medications on cognition, mostly because these are specific to individual medications and there are so many medications and combinations of medications that it is not really useful to talk about medication effects in general.
Mood Related Cognitive Issues
As noted above, depression has major effects on overall brain function. Energized or manic states have effects that can be no less problematic, although, as we will see, they are harder for the person who is in an energized state to notice.
Whereas there seems to be an overall dimmer switch effect with depression, with energized states the effect is more specific. Overall brain activity may be increased, but the area of the brain involved in assessing risk (midline prefrontal cortex) is gradually turned off.
One of the reasons being manic can seem so attractive is that these areas seem to be overactive in depression (scanning for potential problems) with the result that almost any decision or action becomes fraught with potential bad outcomes, and paralysis sets in. So it is a relief when this obsessive focus on negative consequences lightens up. But the effect is not just a reduction to a normal level, it continues until the person is not able to see real and imminent hazards in an action.
In mild states of being energized, the result is that the person feels they are cognitively “at their best” even though they are actually making more mistakes than they usual do, because the monitoring for errors process is turned off.
These neuropsychological tests illustrate the effect.
The first set of tests was done when he was feeling depressed. In fact we did the tests because he felt sure that he had suddenly become demented. The tests show broad reductions in cognitive function in a number of areas.
The second set of tests was done when he was feeling almost normal (perhaps slightly depressed). They show that his cognitive function was much improved (depression is sometimes called 
“pseudo-dementia” because its effects look like dementia, but they are reversible). However, at this point he still felt that his cognitive function was impaired.
The last set of tests were done when he was energized or hypomanic. At this point he felt that he was functioning at his best cognitively. However you can see that in fact he was not doing as well as 
when he was very slightly depressed.
More specifically, when he was hypomanic he made a kind of mistake that is ordinarily very unusual, he “remembered” items from a list that had not actually been on the list in the first place. This is the opposite of the effect of depression, where people usually report that they “don’t know” the answer even when, if they are encouraged to “guess” it turns out that they do.
[For those of you with sharp eyes you might notice that there are some consistent problems across these tests, it turns out that this person has had long standing issues with visual processing and visual memory that have nothing to do with bipolar].Mood Independent Cognitive Issues
Finally, let’s talk about cognitive problems that tend to be relatively persistent, even when the person is not depressed or energized.
There are two types of problems that we often see –
- Problems with sustained attention. There is usually a mild problem with sustained attention (the same problem that people with attention deficit disorder (ADD) which can affect the ability to do things like read a book or concentrate on a complicated problem.
- Problems with processing speed. There is often a slowing down of overall processing speed that affects time dependent tasks like doing standardized tests, or solving urgent problems. Again, this problem tends to be mild.
Readers who are interested in more information on this topic may want to find this review article by Goldberg and Chengappa in the journal Bipolar Disorder. It is a bit technical but summarizes many somewhat confusing studies on this topic.