Some can't say no to alcohol, others can't stop smoking pot. Some prefer the antiseptic high of a pill mass produced in a pharmaceutical clean room, while others crave the soiled rush of a powder purchased on the street and snorted in secret. Familiar to every race, class, occupation, and ethnicity, addiction is the unseen pull of an illicit urge, addiction is the wormhole to a forbidden self. The National Institutes of Health estimate nearly one in 10 Americans over the age of 12 can be classified as a substance abuser or substance dependent. A quick glance at your friends, family, and acquaintances would tell you most anyone can become addicted though some people seem to be more vulnerable than others. The simple question, Why? is not easy to answer, though.

How does addiction work?

Drugs or any addictive substance activate the dopamine-based reward system in your brain, an arrangement of structures and chemical processes which include a cluster of nerve cells known as the nucleus accumbens. This brain region, which lies deep inside your brain, plays an important role in pleasure, learning, aggression, fear, and impulsivity. When we perform an action that fulfills a need or appeases a desire — such as eating to satisfy hunger or having sex to gratify physical cravings — the neurotransmitter dopamine is released into the nucleus accumbens evoking a feeling of pleasure. Scientists refer to this as the reward pathway. Dutifully, your brain records the experiences traveling along this pathway so that you can remember and repeat the behavior resulting in such a pleasant feeling of reward.

This, then, is the basis of one of two separate theories to explain addiction. The learning theory suggests addiction is simply a learned behavior reinforced by the singular properties of drugs. The dopamine "rush" from an addictive substance such as a drug mimics yet also dramatically exceeds both the intensity and duration of the pleasurable feelings aroused by food or even sex. “Repeated exposure to large, drug-induced dopamine surges has the insidious consequence of ultimately blunting the response of the dopamine system to everyday stimuli,” explains Dr. Nora Volkow, director of the National Institute on Drug Abuse. And so the "drug disturbs a person’s normal hierarchy of needs and desires," she adds, and soon an addict has begun to substitute a new set of priorities, all focused on getting and using their drug of choice.

An alternate theory of addiction is the disease theory, which suggests addicts have a biological vulnerability before they ever begin to use drugs. Those who support this view also hypothesize the brains of vulnerable people may have a faulty reward system and so an addict never feels the same level of pleasure from eating, say, or having sex. Disease theory advocates agree with those who support the learning theory of addiction in that they believe continued drug use compounds any damage in the reward pathway.

Generally, then, scientists agree addiction is a disease affecting both the brain and behavior and though anyone can become addicted, environmental and biological factors cause some people to be more vulnerable than others.

Risk Factors

Family history. Just like cancer, diabetes and heart disease, researchers say there is a genetic component to addiction and so some people are born with predisposing genes. While genetic make-up does not guarantee a person will become an addict, those with a family history of addiction and drug/alcohol abuse are more susceptible and find it much harder to quit drugs if they ever start using.

Environment. Home and community contribute to addiction. Living with addicted or abusive parents encourages addiction as does living in a community where drugs and alcohol are commonly abused. Addiction, like obesity, is contagious.

Age. People who first use alcohol and drugs when they are teens (or children) are more likely to become addicted than those who begin in adulthood. Because their brains are still developing, teens are more susceptible to the effects of alcohol and other drugs — the conditions are ripe for addiction.

Psychology. People who are anxious or depressed are more vulnerable to addiction than others. People with ADHD, impulse control problems, and anger management issues are also more likely to become addicts. Personality traits, such as perfectionism and low self-esteem, also contribute to addiction.

Drug of Choice. Heroin, cocaine, and methamphetamine are simply more addictive than other drugs and users of these substances are more likely to become addicted.

Do you have an addictive personality?

While supporting the disease model of addiction, two doctors have taken the theory one step further by arguing all addictions are rooted in the same genetic flaw. “Addicts become addicted not because of the high, but because they need their substance to satisfy their physiological hunger, to relieve the symptoms of depression, and to stave off withdrawal symptoms,” explains Dr. Janice Keller Phelps, who, with Dr. Alan E. Nourse, developed a simple questionnaire based on their shared theory of the biological underpinning to addiction. In fact, they advocated not only detoxification when treating addicts but also nutritional support in their professional practice.

Most importantly, they devised an online test to tell you whether a person is prone to addiction. This addictive personality test takes about 20 minutes and includes five parts — diet, family history, depression, alcohol use, and drug use — each representing a risk factor for addictiveness. While the test has never been scientifically validated, the two sincere physicians who developed it had years of experience in helping those vulnerable to and entrapped by addiction, a subject they pursued for many years.

No matter what your score, remember this: Addiction is no one's destiny, nor is it an incurable illness. While many stumble, many regain their footing, wiser from the experience.