Mood can have a profound impact on cognitive functioning. In fact, over the years, we have found that the most likely diagnosis when someone comes in complaining of “suddenly becoming demented” is a mood disorder (people with dementias tends to have a more gradual onset of symptoms and often don’t notice the impairments).
There seem to be three types of impairments –
1. Mood specific impairments. Meaning the sudden worsening in memory or attention that occurs during an episode of depression or mania. These will respond to treatment of the mood itself… although usually the cognitive impairment responds more slowly than the mood (a rough rule of thumb, once your mood is back to normal you can expect gradual improvement in cognition over the next 2 to 3 months).
2. Impairments that are independent of mood. There seem to be mild impairments in verbal memory and planning and shifting attention that persist even when mood is neither depressed nor manic.
3. Evidence of increased brain aging. People with mood disorders seem to have a higher risk of cognitive problems when they are older. This is correlated with a loss of grey and white matter that can be seen on brain scans (neither of the first two problems are associated with findings that can be seen with typical brain scans). There is some evidence that this may be related to the number and frequency of episodes (severe mood episodes may damage the brain) so that treatment may prevent or reduce this. Lithium has the strongest evidence for a neuroprotective effect.
What to do about this –
Get the most effective treatment to prevent mood episodes, and both their immediate and long term effects on brain function.
Watch for possible toxic effects from medications (perhaps especially with antipsychotic medications), but be aware that the short term and long term episodes of severe mood episodes probably are greater than the effects of medications.
Get plenty of sleep and exercise and a really healthy diet (each of these improves brain function and prevents aging).
This article provides a pretty comprehensive review of this topic –
Goldberg, J. F. and Roy Chengappa, K. (2009), Identifying and treating cognitive impairment in bipolar disorder. Bipolar Disorders, 11: 123-137. doi: 10.1111/j.1399-5618.2009.00716.x