There are differing viewpoints but most addiction experts believe that psychological and biological factors, along with other interrelated factors (including societal, genetic, and environmental) play a role in addiction.
Research tells us that there is a significant overlap between the neurological roots of drug ‘rewards’ and social rewards, for instance. National Institute on Drug Abuse (NIDA) research shows that when there’s an option, rats will choose social interaction before self-administered heroin or methamphetamine. But when those social interactions were punished, the rats turned back to drugs.
Whether psychology or biology plays a greater role than others in addiction is subject to much debate. The short answer is that addiction can be both psychological and biological, and in some cases, they work in tandem to create an unhealthy cycle, likely aided by a confluence of other factors, including environmental.