When do you really attain adulthood?
18. That's when you are legally declared an adult. Right? Oh so you already got the answer. Hey no wait.. we are medical professionals and students of science. So talking in a legal way doesn't always seem right, because from a scientific perspective, adulthood is still an unsolved mystery. Let me tell you about it here..
No doubt physically the school or college going students seem to attain the same height as adults, but their brains are not yet fully developed and matured. Let's suppose a 15 year old commits a crime while playing with his friends, though unintentionally. It is very important to know when to charge the child of such an adult act. Legally, he is a minor. But the age doesn't tell us about the neuro-developmental maturity in this particular child. He could have a thorough understanding of the situation and about what he has done but punishing him to the same level as adults may lead to serious neurologic consequences. So there should be a complete neurologic examination and treatment prior to the investigation.
Talking about the developmental milestones of brain here:
- At about 5 weeks (in utero), the brain is about the size of an apple seed.
- Normal structures of brain and the central nervous system are at their respective places by around 8 weeks, with new connections being made and spreading out.
- At birth around 100 billion neurons are already in place though the new brain weighs only about 25% (one- fourth) of the fully mature brain.
- The size quadruples (four times) by the time the child attains pre-school age.
- At age 6, the size of brain is about 90% of the adult size.
During this booster- period of brain growth, about 700 new connections are formed per second at the time when the child learns its firsts: the first smile at around 2 months, first talk at 1 year of age, and to put on the clothes when the child is around 3 years of age.
In the first decade of life, gray matter (substantia grisea) in the brain and spinal cord grows and expands rapidly. During this period, new neuronal connections (or synapses) are made as the child learns more and more new things and is exposed to new experiences of life.
By the time the child attains puberty, the process of "pruning" initiates and the brain now starts to lose about 1% of its gray matter starting from age 13 and gains about 1% of white matter (substantia alba) from there on. The increase in white matter allows different parts of brain to communicate and connect to each other and form associations to share information better and faster.
(Note: The process of pruning and maturation of brain tends to appear earlier in girls than in boys, which may be due to attainment of puberty that is earlier in girls.)
Neuro-developmental maturation also involves essential protective mechanisms to provide insulating outer cover (the myelin) around the nerve cells and prevent damage from external sources. The process of maturation starts from the back of brain towards the front. This means the part of the brain that attains maturity and becomes fully functional at the last of all is the frontal cortex. This part is involved in the control of movements, memory, problem solving, personality and behavioral changes and many other important functions.
This process of maturation continues until the early 20s with some minor changes until the early 30s. There is no specific age that can be defined when the brain reaches adulthood. It is based on when the child is able to handle situations better and take responsibilities for his actions, able to make important decisions and is not dependent on others anymore.
Understanding the concept of neurodevelopmental maturity in an individual and according to age is important as it can point us towards the specific regions and parts of brain affected in case of neurologic disorders that are considered to be developmental in origin and also to aid in the treatment strategies in such disorders.
- Jaskunwar Singh