system
Given the following post, respond as if you're commenting on Reddit:
human
Neurologically what is the difference between physical and psychological addiction?
gpt
It's a little easier to explain as "chemical addiction" versus "behavioral addiction" rather than physical and psychological, which are very broad ways to look at it. They are also not entirely disconnected, as you can gain behavioral addiction to a chemically addictive substance (think of smokers who quit, but keep wanting to hold a cigarette despite not craving one), or start an addiction for behavioral reasons (a need to escape reality) and become chemically addicted. But they do work with different mechanisms at the most basic level, only to become incredibly complicated when you look at them from a little further away.

A chemical addiction upsets the balance of naturally occurring chemicals within the body, which then reach a new equilibrium, requiring escalating amounts of the outside chemical to achieve the same effects such as euphoria, adrenaline rush, etc, and in turn causing a deficit when there is an absence of those chemicals. This deficit takes awhile to work its way out of the body's natural system for equalizing, which is the source of many withdrawal symptoms. Heroine dependency slowly replaces your body's ability to produce natural 'pain killing' agents. At first, the surplus of the pain killers is euphoric, then as the equilibrium hits, you need more, and in the absence of the drug, you experience crippling pain and physical torment until your body recovers. This will drive you to seek out more of the drug. Then, if you are off of it for a really long time and go back, you could *die* from the dosage you were last adjusted to, as you OD on even... half of it, possibly, because your body has regained its natural equilibrium.

A behavioral addiction is based on using a behavior as an outlet which reinforces that behavior as a source of release. So for example, a behavioral addiction to MMORPGs (not as common as people claim, but not unheard-of) could begin as an attempt to find a social outlet while under the stress of chronic social anxiety, self-esteem problems, or agoraphobia. Then, as it fills a role as a social outlet and the person doesn't experience social anxiety doing it, they reinforce their attraction to that outlet as a coping mechanism. They then slowly become behaviorally dependent on it as an outlet, and it replaces all need for offline socialization in some extreme cases. Then, if removed from it, they panic like they've been cut off from their entire world. This brings out a sort of behavioral "withdrawal" that can drag out extreme anxiety, both buried from before the addiction and newly created by separation from the coping mechanism.

But you will rarely see one without some measure of the other, at least where a controlled substance is involved. On a neuroscience level, it would become more complicated as you get into dopamine reactions involved in learning, which are active in any process involving rewards. Both a chemical outlet (like euphoric escapism) and a behavioral outlet (like cutting as a pain inducer) will involved learn behavior, but the chemical addiction will have the more easily quantifiable methods for detection during withdrawal.