As a physician, medical educator and former animal researcher, I agree that the US national discussion of chimpanzee experimentation should go beyond simple husbandry issues (Nature 474, 252; 2011). For ethical and scientific reasons, it is time for the United States to join other developed countries in ending invasive experiments on chimpanzees.

We now know a great deal about the awareness, intelligence and emotional responses of chimpanzees. Scientists from my organization, for example, have found that invasive experiments on chimpanzees can induce symptoms of depression, anxiety and compulsive behaviours that are similar to mood and anxiety disorders seen in traumatized humans (H. R. Ferdowsian et al. PLoS ONE 6, e19855; 2011).

Although chimps are humankind's closest genetic relatives, we show significant differences in our gene expression, physiology and disease susceptibility. It is becoming increasingly evident that chimpanzee experiments are not improving our understanding and treatment of human disease. Billions of dollars and decades of research using chimpanzees have not produced effective vaccines for hepatitis C, HIV, malaria or other diseases, nor have they provided insight into cancer, neurological diseases or psychiatric disorders. However, the process has inflicted extensive and often lifelong pain and suffering on these animals.