As with nearly every other body part and system, the brain continues to grow for several years after birth. Scientists have consistently studied brain development to determine the age at which the human brain is fully developed. Unfortunately, there is not one specific age where brain development is fully complete.
At the time of birth, most of the brain’s cells are developed and almost all of the neurons the brain will ever have are present. However, these cells and neurons are not fully connected within the brain and require additional time to form their connections.
By age 2, the child’s brain is about 80% of its adult size at approximately 1,120 grams in males. The brain reaches its maximum weight between age 19 and 21 and then begins to gradually lose small amounts of weight after age 50.
By the time a child is 3, the brain has formed nearly 1,000 trillion neural connections, which is about twice as many as the adult brain has. Around the age of 11, the brain will begin to gradually rid itself of unnecessary and inefficient connections.
Although the brain reaches its full adult weight by the age of 21, it continues to develop for several years. In fact, a study done by the National Institutes of Health found that the region of brain that inhibits risky behavior does not fully form until age 25. This is the final stage of brain development.
It is important to keep in mind that although the brain reaches its final stage of development at age 25, learning continues throughout the life span. The neural connections of the brain continue to form, change and redirect when confronted with new experiences and ideas.