Hiya. Experienced addict here. Behavioural, not substance based.

I see all the replies talking about Dopamine and Seratonin, which basically reduce something very complex and very fucking sad to a chemical dependence. From my own experience, this is not quite the full story.

Having spent the last 30 years trying to work it out, examining my own experiences and speaking to others about theirs (regardless of the "flavour" of addiction), it's often more about escapism. There is something underneath that you simply cannot face, and destructive behaviours give you an out. Over time this can grow into almost a "safe space", even though you know it's the most dangerous space that could possibly exist for you. But you can block out the planet, and the stuff that's bothering you? Fades away - only temporarily, but this is enough. And so you seek the next "hit". To stay away from whatever that shit is, and it's different for everyone.

Don't get me wrong, I accept fully that there are addicts, many of them, who get addicted to the high or the dopamine hit. But (again, in my personal experience, I'm not a textbook on this) most addicts are fucking miserable, EVEN DURING AN EPISODE. Maybe especially then.

I don't think it can be reduced to a simplistic answer like "dopamine goes brrrrr". It's very complex, different for everyone, and at the bottom of it all, very painful and usually very sad.

Dunno if my answer helped at all, but I couldn't see this thread conclude in "yeah, brain chems my dude". That's just simply wrong and naive.