Why Do Addicts Act Irrationally?
Addiction is a disease of fundamental irrationality. Addicts continue to use drugs despite worsening physical, social, psychological, and often, legal consequences, even the threat of death. No rational person would do this, but addicts do.
Why are addicts irrational when it comes to drug use?
Because addiction is a disease that alters one’s motivational systems. Drug abuse causes significant changes to the neurons and neurotransmitters in the brain’s Reward System, the network responsible not only for feeling pleasure, but also central to learning, memory and motivation. Addiction is a form of toxic learning that results in malignant memories and motivations, over-stressing the pleasures of drug use and under-valuing the repercussions. 
Neuroscientists say that drug abuse shifts the normal balance between emotional imperatives and rational checks-and-balances overwhelmingly in favor of the immediate emotional need for drugs. This is most often seen in addicts’ denial that they have drug problems even after it’s become readily apparent to everyone else. That and fear of withdrawal combine, creating conditions where addicts will do crazy things in furtherance of drug-taking.
The word “irrationality,” however, invokes negative connotations and doesn’t adequately describe how automatic continued drug use is for an active addict. In truth, it feels instinctive. Since the Reward System pre-dates the evolution of rational human brain networks, it may be closer to the truth to label it “pre-rational,” rather than “irrational.”
