Yet sales figures for certain neuro-psychotropic drugs are considerably higher than the incidence of the illnesses for which they are indicated would lead one to expect. This apparent paradox applies above all to neuropsychotropic drugs that have neuro-enhancement properties. The most likely explanation is that neuro-enhancers are currently undergoing millions of self-trials, including in universities – albeit probably not in their laboratories. The ten top-selling psychotropic substances in the USA include anti-depressants, neuroleptics (antipsychotics), stimulants and drugs for treating dementia.