Can masturbation play a role in this addiction?
Of course, but masturbation is not required. That said, frequent ejaculation in animals leads to several brain changes that inhibit dopamine, and thus libido, for several days. Under normal circumstances, sexual satiety (defined differently for each species) leads to males taking a time out from sexual activity. Sexually satiated porn users may override these inhibitory mechanisms by escalating to extreme porn, or spending more time watching. Both goose dopamine. Pushing past “I’m done” signals can lead to the accumulation of DeltaFosB. Certainly, eating to obesity causes the accumulation of DeltaFosB. However, without the lure of Internet porn, how many guys would just give it a rest? Most all. For more, see Does Frequent Ejaculation Cause A Hangover?
Note: I read many of the threads that link to YBOP. Most debates about porn addiction (existence or effects) devolve into debates about masturbation. This is nonsensical and completely muddies the discussion. YBOP is only concerned with Internet porn use, not the pros, cons, or frequency of masturbation.
via Start here for an overview of concepts & science | Your Brain On Porn.