Originally Posted by pinworm

The proper medical definition of "addiction" is the replacement of a neurotransmitter that then ceases to be produced in favor of the drug. If the drug is ceased suddenly, the lack of the neurotransmitter causes withdrawl. For example, nicotine replaces acetylcholine.

Anything else is a "habit" despite our tendancy to call them "addictions". One cannot be "addicted" to porn, games, love, television, travel, sex, marijuana, or the internet. Those "habits" may have strong neurochemical bases such as the release of dopamine, serotonin and norepinepherine, but those are not alien substances or replacements..there is a psychological event around their release triggered by those activities. But they are not properly addictions.

They are still serious though, and can have similar impacts to addictions on the lives of those who engage in obsessive and repetitive behaviors: relationships, health, and professional lives can all fall apart.