It was claimed, by professor Sunha Ji of Yonsei University, that the suicide probability of short, thin people with low level of cholesterol is relatively high. Professor Ji and her team with the National Health Insurance Corporation have found and researched 472 Korean people who had committed suicide from 1992 to 2009. It is interesting that three unrelated traits, height, level of cholesterol, and degree of obesity, are all claimed to be the possible cause of suicide.
The professor Ji has claimed that “the reason why the people with low level of cholesterol are more likely to commit suicide might be the factor of controlling emotions of the cholesterol.” She has also claimed that “the decline in growth caused by mental stress during childhood might have an influence on suicide.” It seems that her claims are somewhat reasonable, but clearly they are not in terms of critical or scientific thinking.
First of all, the criteria of whether tall or short in terms of height is ambiguous, and the study was also limited to Koreans whose number was too small to be used to define the causality. Secondly, the conditions of each group other than their height, degree of obesity, and the level of cholesterol were not controlled. That said, there might have been a 3rd variable that had influence on their relationships. Therefore, the study conducted by professor Sunha Ji and her team can be said that it has neglected one of the principles of scientific thinking: correlation isn’t causation.