13 May 2009 Medical Meanderings
When Good Brains Go Bad ©
Your crystal ball is where you chase the dragon / She said, now bring me home his head inside a sack…Got to get that monkey off your back…
- Aerosmith, “Monkey On My Back” (1989)
Unlike plants, we animals get to move around. Because those that apathetically sit and wait for food, water and mates generally die or get eaten by competitors (at least until modern times), we have inherited brain systems that motivate us to seek out what we need for survival. When we satisfy these hard-wired, inborn drives, it gives us pleasure and makes us more likely to repeat the behavior.
Several brain circuits handle these complex motivational tasks, but one of the biggest drivers is a cluster of nerve cells called the nucleus accumbens (uh-KUM-bins). When we do something rewarding (eating, sex, etc.), the nucleus accumbens is stimulated, causing signaling of several further areas of the brain, including the areas that encode memory, enable movement and direct attention. These circuits ensure that we’ll remember what felt good, how we got it, and that we’ll look for another opportunity in the future.
Addiction hijacks this necessary brain circuitry. The word “addiction” has a very specific medical meaning: the continued, compulsive drive to use a substance despite serious adverse consequences to the user. Despite financial ruin, damaged relationships or medical illness, his brain’s reward circuitry has changed in such a way to undermine voluntary control and drive him only toward the next “fix.” In the addicted brain, the usual levels of neurotransmitters have been altered, which results in craving and the misery of withdrawal. Areas providing impulse control and direction of attention are less active than in normal brains, impairing the addict’s “willpower” and ability to see the bigger picture. Laboratory rats will press a lever to dose themselves with addictive drugs, neglecting food, water and mating until they die. The smoker puffing through his tracheostomy hole, the malnourished alcoholic or meth user, the gambler who loses his daughter’s college fund, on and on…we do much the same.
Genetics contribute about 40-60% to an individual’s risk of addiction. For example, genes linked to an increased or a decreased risk (depending on the mutation) of addiction to alcohol, nicotine and codeine have been found. However, genetics are certainly not the whole story—environment, exposure and the choice of repeated use have equally large role in addiction.
As scientists understand more about what goes wrong in the addicted brain, we have more tools to assist those who want to end their addiction. Unlike rats, we humans have huge brains we can also employ to break free of addiction, though “cure” is elusive. Medical help is sometimes necessary to prevent serious withdrawal illness, or to ease the transition. Several medications have become available in recent years to block drug-induced reward and lessen withdrawal. Support groups and addiction counselors can also help the addict re-wire his altered brain, learn new ways to think and live without the drug, and regain control over his attention, memory, mood and life.