The brain is the last human organ to develop fully, but only recently has science established that it isn’t fully grown until a person reaches about 30 years of age.
This helps to explain why behaviour during the teenage years – when an adolescent body is also exploding with hormonal changes – may sometimes be erratic, apparently unreasonable and often frustrating. The fact is their brains are trying to keep up with the rest of their bodies.
Philip Watkins, an Australian-trained, Hong Kong-based naturopath, with more than a decade of clinical practice treating clients of all ages, explains the cerebral changes during what has been called a time of “tinderbox emotions”.
The brain evolves both structurally and functionally during adolescence, he says. During this time, “synaptic pruning” occurs, a process in which connections in the brain that are used often are strengthened through repetition, and connections that aren’t used so much are weakened.
https://www.scmp.com/lifestyle/health-wellness/article/3010038/understanding-teenage-brain-how-parents-can-avoid