Although researcher Dr. Sarah Bailey noted that it was impossible to ask a mouse if it is depressed, they could observe and model its behavior through two tests. The first involved causing the adolescent mice stress by forcing them to swim, while the second induced stress by suspending the mice by their tails.
Normally, a mouse will swim, climb or struggle, and only periodically stop in a period of resignation. A depressed mouse will remain it its resigned state longer than one that is healthy. The mice given human-equivalent doses of Accutane tended to show increased depression-related behavior.
Accutane is a member of the drug class known as retinoids, which have been shown to affect the way the body reads genes. Use of the drug while pregnant is known to damage fetuses and reduce the amount of brain cells that they generate, which is why precautions are taken to ensure women who are pregnant or who may become pregnant do not use the drug, but recent studies suggest that brain-cell generation may be equally important in adolescents and adults. Bailey suggested Accutane might also interfere with the body's production of the mood hormone serotonin.
While evidence from the more than 13 million users of Accutane worldwide suggests that only 5 to 10 percent experience the side effect, retinoids have also been implied in connections to Alzheimer's disease and schizophrenia, so doctors are eager to understand how the drug works.
Accutane maker Roche claims, "While no causal link has been established between Accutane and either depression or suicide, we are constantly monitoring all available safety databases on Accutane worldwide." However, the World Health Organization has reported 720 cases of psychiatric problems linked to the use of Accutane, including 84 suicides and suicide attempts.