Thirty years of teaching college students about the effects of drugs upon their brains and I am still astonished at the continued attraction of illicit drugs. Year after year, the story never really changes. Their reasons for taking psychoactive drugs are varied but their rationalization has remained fairly consistent: they simply do not believe that anything truly bad will ever happen to them. They are young, their lives stretch out before them to the horizon and they feel immortal. I speculate that the consistency of this reasoning across decades is likely due to a developmental feature of the human brain.
I blame the feelings of immortality of teenagers on the fact that their frontal lobes are not fully working. The reason the frontal lobes are not fully engaged is because they have not yet completed the process of neuronal myelination. Think of myelination as the insulation on the electrical wires inside your house. Without myelination in the brain, electrical signals from neurons fail to reach their destination. The parts of our brains that myelinate last are also the parts that evolved most recently. These parts include our frontal lobes, which contribute most to our unique personalities and allow us to anticipate the consequences of our actions. Essentially, your frontal lobes tell you that it's a bad idea to drink alcohol and drive or to ignore the consequences of taking heroin. When your frontal lobes finally complete their process of myelination, they begin to work properly and you stop doing dangerous things. Most importantly, you stop feeling immortal. Apparently, women finish this myelination process by age 25 years and men finish by age 30. Thus a 20-year-old female, although her brain is still myelinating, is closer to maturity than her 20-year-old boyfriend, who still has another 10 years before he can really appreciate the wisdom of warnings such as those against drinking and driving or against taking any drug that comes his way.
Whenever I discuss this developmental process during class the young women all nod their heads knowingly; finally they have an explanation for the behavior of their boyfriends or certain members of our ATO fraternity. The delay in our access to our frontal lobes, as well as any insight into our own mortality, also correlates with another phenomenon familiar to parents with college age children - car insurance rates. Young women always get a break on insurance rates at a much younger age than men simply because their frontal lobes are wired up sooner. The condition of the female frontal lobes translates into a history of young women having fewer driving accidents than young men of a similar developmental age. I can imagine a future time when we'll need to carry a recent MRI image of our frontal lobes in order to buy alcoholic beverages or vote. Young men might start carrying pictures of their fully myelinated frontal lobes to show worried parents when picking up their dates. Just think of the possibilities!
See also: Marijuana and Coffee are good for the brain. http://www.youtube.com/watch?v=2uVXs6CY2ps
© Gary L.Wenk, Ph.D. author of Your Brain on Food (Oxford, 2010); http://faculty.psy.ohio-state.edu/wenk/