Memory and/or cognitive problems are the rule rather than the exception in people with mood disorders1. There are a number of reasons for this and figuring out the best approach to these problems is tricky.
Mood episodes (episodes of mania, hypomania or depression) appear to be harmful to the brain. Studies find that those with the largest number of episodes are much more likely than the general population to have evidence of white or gray matter abnormalities that can be found also in those with dementia2. This doesn’t mean that these people have dementia, but it is a worrisome finding and one reason why early and effective treatment seems so important. Other studies find that there are lower levels of brain derived neurotrophic factor (sort of a natural brain cell “growth hormone” that keeps brain cells healthy) in people with mood disorders, and that these lower levels improve with effective treatment3.
There are at least two ways that depression affects cognitive functioning4:
- Cortisol, the stress hormone that is increased with anxiety, is often increased in people with depression and elevated cortisol is associated with short-term memory impairment.
- Depression itself seems to be associated with slower brain activity. The more severe the depression the longer it takes to solve problems.
People with mood disorders often have anxiety. In fact, for many, many people with bipolar disorder, high levels of anxiety in childhood are the first evidence that there is any kind of psychiatric disorder. Anxiety (as well as depression) is notorious for causing difficulty remembering things. Memory seems to function best at low to moderate levels of stress (measured as high levels of the stress hormones cortisol and adrenaline)5. Above those levels cortisol has a direct negative effect on the functioning of the hippocampus, which is the brain’s card catalog for finding memories and filing memories. So treating anxiety (and depression) almost always improves memory and cognitive functioning.
Episodes of depression and hypomania or mania may have an effect on cognitive functioning that lasts longer than the mood episode6. We find, and newer studies support this view, that once the mood symptoms are controlled it takes an additional six to nine months for the brain to return to its baseline functioning. This is often why a quick return to work or school can be impossible.
Also, studies tend to find that people with bipolar disorder are more likely than the general population to also have attention deficit disorder7.
With so many potential confounding factors the most important first step is to get your clinician to do a very careful assessment for comorbid anxiety, attention deficit disorder and inadequately treated mood symptoms.
1.Austin M-P, Murray C, O’Carroll RE, et al. Cognitive function in major depression. (1992) Journal of Affective Disorders. 25(1) pp 21-29.
2. Beyer JL, Young R, Kuchibhatla M, Krishnan KR. Hyperintense MRI lesions in bipolar disorder: A meta-analysis and review. Int Rev Psychiatry. 2009;21(4):394-409. Review.
3. Lee BH, Kim YK. The roles of BDNF in the pathophysiology of major depression and in antidepressant treatment. Psychiatry Investig. 2010 Dec;7(4):231-5.
4. Reppermund S et al. Persistent cognitive impairment in depression: The role of psychopathology and altered hypothalamic-pituitary-adrenocortical (HPA) system regulation. Biol Psychiatry 2007 Sep 1; 62:400.
5. LeBlanc VR. The effects of acute stress on performance: implications for health professions education. Acad Med. 2009 Oct;84(10 Suppl):S25-33. Review.
6. Robinson LJ, Ferrier IN. Evolution of cognitive impairment in bipolar disorder: a systematic review of cross-sectional evidence. Bipolar Disord. 2006 Apr;8(2):103-16.
7. McIntyre R. Bipolar disorder and ADHD: Clinical concerns. CNS Spectr. 2009 Jul;14(7 Suppl 6):8-9; discussion 13-4.