Irrespective of the animal-rights issues you discuss, we disagree with your one-dimensional view that addiction is a disease, and with your claim that this view is not particularly controversial among scientists (Nature 506, 5; 2014). Neuroscience has been widely documented as just one of many important influences in drug addiction.

Substance abuse cannot be divorced from its social, psychological, cultural, political, legal and environmental contexts: it is not simply a consequence of brain malfunction. Such a myopic perspective undermines the enormous impact people's circumstances and choices have on addictive behaviour. It trivializes the thoughts, emotions and behaviours of current and former addicts. It also belittles the significant effect that public-health campaigns and legislation exert on curbing substance abuse.

Addiction is too complex to be fought on a medical-research front alone. A variety of approaches based on diverse levels of analysis is required.