Adolescent behavior that motivates youth to experiment with drugs of abuse can be directly related to the state of brain development. During adolescence, there is a restructuring in the production of endogenous opioids, which cause a hedonic effect. Changes in neurodevelopmental circuits within the prefrontal cortex and in the reward system also increase the vulnerability of youth to such behaviors during adolescence.
“Studies in humans and animals show adolescents react more strongly to reward than adults and children. Teens display greater activity in the nucleus accumbens — a component of the brain’s reward system — than adults or children when completing a simple task for a reward. Neuroscientists believe both the revved-up response to reward and the underdeveloped impulse control center lead teens to greater thrill-seeking”. (http://www.brainfacts.org/across-the-lifespan/youth-and-aging/articles/2011/teen-brain-vulnerability-exposed/)
USE OF ALCOHOL AND MALADAPTIVE NEUROPLASTICITY
Adolescence is a critical period of great neuroplasticity of prefrontal circuits, a plasticity that leads to an enhancement of cognitive abilities: abstract reasoning, concentration and learning. However, this is also a period of high behavioral vulnerability. The desire for new experiences may lead to inappropriate decisions and impulsive actions that are results of the immaturity of orbitofrontal circuits, and that may predispose adolescents to alcohol consumption. (1) (2) The orbitofrontal cortex is responsible for impulse control and the ability to anticipate the consequences of our actions. (3)
Romeo and Juliet as an exemples of adolescent brains:overresponsive reward system leading to passion? Impulsive decisions due to prefrontal cortex immaturity?
MONTAGUE (speaking about Romeo):
Many a morning hath he there been seen,
With tears augmenting the fresh morning dew.
Adding to clouds more clouds with his deep sighs;
But all so soon as the all-cheering sun
Should in the furthest east begin to draw
The shady curtains from Aurora’s bed,
Away from the light steals home my heavy son,
And private in his chamber pens himself,
Shuts up his windows, locks far daylight out
And makes himself an artificial night:
Black and portentous must this humour prove,
Unless good counsel may the cause remove.
Romeo and Juliet by Willian Shakespeare (Act 1, scene I)
Ah, Juliet, if the measure of thy joy
Be heap’d like mine and that thy skill be more
To blazon it, then sweeten with thy breath
This neighbour air, and let rich music’s tongue
Unfold the imagined happiness that both
Receive in either by this dear encounter.
Romeo and Juliet by Willian Shakespeare (Act 2, scene VI)
Decisions and impulsive actions that can lead to alcohol abuse are consequences of dorsolateral prefrontal circuits, one of the last areas of the brain to mature. These circuits are responsible for impulse control, working memory and the ability to design a mental scheme that relates the causes to the consequences of one’s acts. Immaturity and the late development of these circuits explain the reckless behavior of teenagers, which results from an inability of the brain to suppress impulsive action. (3)
Among the neuroadaptations that may contribute to the development of alcohol dependence is behavioral sensitization, defined as the stimulating effect that arises after repeated administration of the same dose of ethanol. During the ensuing state of awareness, there is a greater value in the response that dopamine mediates to the motivational encouragement that drugs provide to the striatum and amygdala. This enhanced response coincides with a weakened activity of the prefrontal cortex, reflecting a weakened inhibitory control over the hyperactivity of the amygdala-striatal system. This in turn weakens the ability of the adolescent individual for self-regulation of the drug-seeking behavior, leading to persistent and compulsive use, with long-term negative consequences.
An emerging synthesis is that drug abuse is a stereotyped behavior driven by maladaptive neuroplasticity in subcortical reward circuitry, and which is highly resistant to reversal, making it difficult to establish new behaviors for adults who abused substances as teenagers. (4)
Thus, it is understood that sensation seeking and testing of limits, observed in adolescence, are reflections of a brain that is developing and vulnerable. (1) (2) Thus, the behavior that motivates adolescents to experiment with addictive substances can be directly related to their state of brain development and circuit neuroplasticity.
Dryeli Cássila Kindler, Fabiano Fugita, Heloisa Davanso e Larissa Leite Martins- Acadêmicos de Medicina-XIIa turma, FCS-UFGD
(1) Joel Swendsen; Marcy Burstein; Brady Case; Kevin P. Conway; Lisa Dierker; Jianping He; Kathleen R. Merikangas. Use and Abuse of Alcohol and Illicit Drugs in US Adolescents Results of the National Comorbidity Survey–Adolescent Supplement. Arch Gen Psychiatry. Vol. 69, n° 4: 390-398, 2012.
(2) Rolls, E. (1999). The functions of the orbitofrontal cortex. Neurocase, 5, 301-312.
(3) Cristian V. Alencar. Por que me comporto assim? Transformações cerebrais na adolescência. Revista Uibrasil, 2009.
(4) Cramer SC, Sur M, Dobkin BH, O’Brien C, Sanger TD, Trojanowski JQ, Rumsey JM, Hicks R, Cameron J, Chen D, Chen WG, Cohen LG, deCharms C, Duffy CJ, Eden GF, Fetz EE, Filart R, Freund M, Grant SJ, Haber S, Kalivas PW, Kolb B, Kramer AF, Lynch M, Mayberg HS, McQuillen PS, Nitkin R, Pascual-Leone A,Reuter-Lorenz P, Schiff N, Sharma A, Shekim L, Stryker M, Sullivan EV, Vinogradov S. Harnessing neuroplasticity for clinical applications, 2011.