How Do Drugs Affect a Lie Detector Test?

Antidepressant medications such as lithium, Prozac, Valium or Xanax can cause skewed results on polygraph tests, claims American Polygraph Services. However, it goes on to state that these results are immediately visible during the pre-test process, and it is up to the examiner to determine whether or not a subject can take a polygraph while on those drugs.

Polygraph tests, commonly referred to as "lie detector tests," are conducted with the use of a physiological recorder that is able to assess blood pressure, respiration and skin conductivity, as noted on The accuracy of polygraph testing has been a subject of controversy for a long time, explains the American Psychological Association. There is no evidence that the human body undergoes any unique physiological reactions. Therefore, someone who is being honest could theoretically have a reaction to a question, while a dishonest subject would not.

There are three phases to a polygraph tests, according to information published by the American Polygraph Association. The first phase is the pre-testing phase, followed by the testing phase, and the final phase is the analysis of the data. It is necessary to very carefully complete each of these steps to ensure the testing results are as accurate as possible.