Ask Dr. K: People prone to addiction may be wired differently

The use of illicit drugs and alcohol takes the lives of nearly 300 people every day in the United States. (Tobacco takes more than 1,000 every day.) Though most did not become famous in the way that Philip Seymour Hoffman and Whitney Houston were, each had friends and family who mourn their passing.

Fortunately, not every person who drinks alcohol or tries drugs becomes dependent. Why, then, do some people develop addiction while others do not?

Our genes account for about half of our risk for addiction. The environment in which people grow up and their personal histories also play an important role. People who were abused or neglected as children, for example, have a higher risk of developing addiction than children who were nurtured. People with mental illness are also particularly vulnerable.

Still, although some people are more at risk for addiction than others, nobody is immune to addiction. That’s because we are all wired to respond similarly to rewards.

The brain registers all forms of pleasure in the same way: by releasing the neurotransmitter dopamine in the brain. That’s true whether the pleasure originates with a drug, a monetary reward, sex or a satisfying meal. (I’ve put an illustration of this reward pathway on my website, AskDoctorK.com.) But drugs of abuse, such as nicotine or heroin, release two to 10 times the amount of dopamine as do natural rewards — and they do it more quickly and more reliably.

It’s possible that people who get hooked more easily have a more robust dopamine response. In some way, they are “wired differently.”

I saw Philip Seymour Hoffman play Willy Loman in “Death of a Salesman.” As the play opened, the stage was unlit. At the far left was a luminous blue light, like the sky at the end of a clear day. A man carrying a briefcase in each hand, Loman, is seen in silhouette. He is stooped, trudging slowly, as dejected as a person can be. The road had not been kind. No one was buying.

He opens the door to his home, his family waiting for him inside. Suddenly, he is the salesman: confident, jostling with his sons, talking about what a success the trip had been. Playing the role he had to play, to avoid taking his own life.

I will remember that entrance, and many other moments from Hoffman’s films, all of my life. Acting doesn’t get any better. Gone, just like that.

We have to solve the plague of addiction, and we will. In the past 20 years, scientists have learned a lot about the brain chemistry of addiction. That knowledge will lead to better treatments.

Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.