Bipolar disorder: Effects on the Brain and Behavior

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Bipolar Disorder: Effects on the Brain and Behavior

This paper provides an analysis of bipolar disorder. First, the neurological basis of bipolar disorder will be explained. Second, the behavioral symptoms and functional deficits associated with bipolar disorder will be discussed. Third, the biological and environmental factors implicated in the onset of bipolar disorder will be described. Fourth, therapeutic and pharmacological methods used to treat bipolar disorder will be evaluated. Fifth, the prognosis for people with bipolar disorder will be discussed.

The Neurological Basis of Bipolar Disorder

According to DelBello, Zimmerman, Mills, Getz, and Strakowski (2004), "neurofunctional and neuropathological studies have implicated the amygdala as a primary brain region involved in the regulation of emotion" (p. 49). In the study by DelBello et al. (2004), they used "thin-sliced magnetic resonance imaging (MRI) scans of adolescents with bipolar disorder" to determine areas of the brain involved in this disorder (p. 43). They hypothesized that the amygdala, putamen, thalamus, and globus pallidus would be the region's most involved in bipolar disorder. Total cerebral volume and the caudate nucleus were other regions of interest (ROI). Other researchers had found that there is "a limbic-thalmic-prefrontal circuit and a limbic-striatal-pallidal-thalmic circuit" (DelBello et al., 2004, p. 43).
Adolescents were studied by DelBello et al., moreover, because bipolar disorder is thought to have a genetic basis, and because there are fewer confounding variables such as substance abuse disorders and exposure to medications. However, some of the participants did have co-occurring substance abuse disorders because it has been found that "30% of bipolar adolescents may also have a substance use disorder" and to alleviate them would have reduced the ability to generalize this study (DelBello, 2004, p. 45). Thin-slice MRI scans were used because they are more accurate. There were 23 mixed or manic participants with bipolar disorder and 20 healthy participants involved in the study by DelBello et al. (2004).
Results

The results showed that the bipolar adolescents had several neurological differences compared to the controls. For one, the bipolar subjects had significantly smaller total cerebral volume than the controls. Two, the bipolar subjects had larger putamen volumes and a smaller amygdala than the controls. Three, length of substance abuse had no correlation with the results, but duration of illness was negatively correlated with amygdala volumes, and smaller amygdala volumes were positively correlated with lifetime antidepressant exposure. Four, age of onset, family history of a mood disorder, and current exposure to antidepressant or antipsychotic medications did not have a statistically significant correlation with the ROIs.

The only large effect size was that the adolescents with bipolar disorder had a smaller amygdala volume than the normal subjects. Also, in contrast to the healthy subjects and studies on adults, the bipolar adolescents had smaller total cerebral volume. However, "future investigations examining whether the reduction in total cerebral volume in bipolar adolescents that we report is due to the age-dependent relative decrease in gray to white matter volumes are necessary" (DelBello et al., 2004, p. 49). Because the adolescents were close to the age of illness onset, this could explain why a statistically significant ...