A Final Common Pathway of Addiction:
Recently, at a clinical conference on addiction, I overheard an intern ask a straightforward question about why a person recovering from a severe cocaine addiction should not consume alcohol, a drug they never really had a problem with. As it turns out, this is a common question asked by both clients as well as their spouses, families and friends (who often want to be able to drink socially with them). Seasoned clinicians, long-standing AA members and others who have successfully managed their addictions all seem to understand that a person battling a substance use disorder will be at a serious risk of relapse or “cross-addiction” if they start drinking or using another drug. The question as to why this is the case is of great interest medically and, as it turns out, has major implications not only for promoting abstinence among those with addictive disorders, but also for one day developing medical treatments that can directly target brain areas that are directly involved in both addiction and recovery.
Over the past twenty years, advances in brain imaging and neuroscience have greatly enhanced our understanding of several aspects of addiction. For a really good and technical overview read the article: (Nestler EJ. Is There a Common Molecular Pathway For Addiction? Nature Neuroscience. 8(11):1445-9, Nov 2005). One of the most interesting findings has been that when drugs of abuse are absorbed by the brain, certain important areas become activated in a predictable manner. This is only true for drugs that can be abused and/or cause addiction, and not true for drugs or other substances that cannot. The areas that “light up” on fMRI scans during ingestion of drugs of abuse are located deep in the brain in an area called the ‘mid-brain’ (see fig. 1) which is considered to be responsible for feelings of reward, pleasure, euphoria, compulsion, salience, and perseveration. Although different drugs of abuse cause a variety of feelings when ingested (e.g., cocaine, alcohol, marijuana and heroin have very different effects emotionally and physiologically), they all have a very similar effect on these sensitive yet powerful mid-brain areas. These areas activate very quickly and, frequently unbeknownst to the person. In fact, it has been clearly demonstrated that these important brain areas become activated even before the addicted individual actually ingests an addictive substance! So, when an alcoholic walks into a bar, or sees a beer commercial on television, it is quite likely that her mid-brain is firing and activating – a situation that probably accounts for what is known as “cue-induced relapse”.
There are three major reasons why this is important. First, if highly sensitive mid-brain areas can be activated by thoughts, sights, smells, etc…it is a very good reason why those with addiction need to avoid people, places and things associated with drug use. Second, as it turns out, the mid-brain communicates directly with the frontal part of the brain, the area responsible for decision making, weighing risk vs. reward, and managing impulsivity. In those suffering from addiction, the frontal brain areas (which by comparison activate slowly), seem to be overwhelmed by the impaired mid-brain areas which continuously fire and dominate the person’s actions and behaviors. Finally, since all drugs of abuse have a common effect upon sensitive mid-brain areas that are associated with feelings of reward, pleasure, euphoria, compulsion, salience, and perseveration, then it stands to reason that a person who suffers from an addiction to one substance should avoid ALL substances that could cause addiction!
Scott Bienenfeld, M.D.