Research Methods in Clinical Psychology

1) Before treatment, did the groups significantly differ on Body Mass Index (BMI), age, or ventricle volumes? Provide and explain the relevant analyses. If the groups did differ, exactly how did they differ?

Yes, controls, and bulimic and anorexic patients differed on pre-BMI, age, and pre-ventricle volumes. Anorexia-Bulimia and Anorexia-Controls differed along BMI scores and ventricle volumes before treatment: F(2, 54)= 20.80, p 0.05.

5) Which group(s) demonstrated a significant change in ventricle volumes from Pre- to Post-Treatment?

Only the Anorexia group showed a statistically significant change in ventricle volumes before and after treatment--t(9)=8.0, p < 0.001. The ventricle volume decreased from almost 17 to about 15. The correlation was significant at p=0.016, r=0.73. However, controls and bulimics did not show a statistically significant change in pre- and post-treatment ventricle volumes. Bulimics' pre- and post-treatment ventricle volume change was t(9)=1.94, p=0.08. However there was a strong positive correlation with an r of 0.95. In controls, there was also a strong positive correlation with an r of 0.95, yet there was no statiscally significant difference before and after treatment in ventricle volumes for this group--t(9)= - 0.65, p=0.53.

6) Create and print out a bar graph showing the change in ventricle volumes across time in each group. Based on results of the above analyses, what conclusion might you draw regarding eating disorders, ventricle volumes, and BMI? What do large ventricles indicate?

For anorexics, ventricle volumes decrease as BMI increases. Compared to normal, healthy controls and bulimics, ventricle volumes appear static over time. Perhaps ventricle size shrinks because of dehydration, or perhaps this suggests some other link between low BMI and other serious disorders, like schizophrenia or dementia. It also seems that there is a cut-off for ventricle volume enlargement--BMI must be below 20 for an increase in ventricle volumes. It also seems that once ventricle volumes have increased they cannot return to completely "normal" sizes (in comparison to healthy controls). Although post-treatment BMI's are somewhat similar for controls and bulimics, ventricle sizes in controls is slightly lower--perhaps having a serious eating disorder like bulimia or anorexia permanently changes brain structure even after