This lays it out pretty clearly.  The tricky part is:
-  a genetic lack of dopamine receptors, inherited from one or both parents
-  leads to the brain continually feel starved for dopamine, on edge and can drive, sometimes  "sucessful", externalizing behavior
-  the dopamine starved brain overrides conscious control to drive external dopamine inducing behaviors: sex, eating, risky behavior, etc - think cutting to.  Guys brains act out, girls act in.
-  problem is can never get enough.  Externally triggered dopamine is very energy consuming and can't substitue for a systemic brain flaw, more behavior may raise need instead of soothe



Result - life gets very ugly.   Again, the addictive behavior is a symptom, NOT the problem/illness. 

What's often misleading about descriptions of addiction, and this video, is they talk about/show only the dopamine inducing result but don't explain the underlying brain deficits these poor folks are born with that causes the behavior.  

Moral weakness, lack of self-control, impulsiveness, personality problems, irresponsibility, bad people?   That's the easiest way to explain these tragic conditions.   Not medically valid, but our minds like easy answers of things we can't quickly understand.  Making things up works pretty well. 

Many illnesses used to be seen as moral weakness.  Wasn't the Black Death believed to be a god's judgment against sin?   

If I was suffocating from an acute lung disorder, I'd be doing some wild things and running around.  Somehow when it's the brain, we dislike the idea it can be sick like any other organ.

That's not going to change in our lifetimes but the science is kind of cool!