Hi Chunky, good question. Although I lack the personal experience of the person you ask my education is in the healthcare field so allow me to take a shot at answering for you.
Essentially there are two types of addiction, (1) Physical dependence, and (2) Mental Addiction.
Physical dependence requires use of a substance (like alcohol, opiates, benzodiazepines, nicotine et cetera), that when withdrawn creates negative physical symptoms. Opiates are a great example. After a certain amount of time, and dose, the body habituates to that level of opiates. If you stop taking them you will experience withdrawal symptoms. A few of these symptoms are; piloerection, nausea, vomiting, pain, sweating and several others. The symptoms depend on the receptors the drug binds to so they vary between substances.
Mental addiction can occur with substances such as cannabis, antihistamines and behaviors such as gambling, lying, stealing et cetera. The signs of a mental addiction are increasing use without physiological requirement, hiding usage, and a compulsion to use a substance despite its negative impact on your life. Mental addiction and physical dependence frequently occur together. However it is the mental addiction component that ruins lives. Mere physical dependence is not enough.
A good example would be a contributing member of a social forum that begins making belligerent, bigoted, insane and nonsensical posts that lead to their social ostracism. Instead of moderating their behavior and discontinuing the use of the substance, or behavior, they spend multiple hours a day engaged in cleaning, editing and deleting their posts in a vain attempt to deny their disorder.
