At 18 we are officially considered adults. However, the brain lags somewhat behind and its development is only completed in the mid to late twenties.
When does the brain stop growing? It depends on which part we are talking about. Broadly speaking, the brain is made up of two structures: gray matter and white matter. The gray matter consists of nerve cells and the white matter consists of their processes, i.e. the connections between the nerve cells that are responsible for communication. MRI studies have shown that gray matter grows until around age 25 and white matter grows until age 30.
By the age of six, the volume of gray matter initially increases significantly. This allows us to adapt well to the environment in which we grow. The increase usually begins in the brain regions that process sensory information.
From the age of six onwards, this growth stagnates and from puberty onwards the volume of gray matter decreases slightly. It sounds strange, but it is logical: after all, energy is needed to drive nerve cells. The brain only retains cells that are used a lot and have already made many connections. As a result, the brain becomes more and more efficient.
Not all brain regions develop at the same rate. For example, there are so-called sensitive or critical phases in which children react particularly sensitively to certain stimuli, which makes it easier to learn new things. Difficult languages ​​in particular are best learned before the age of ten, and the sensitive phase for distinguishing between speech sounds is limited to the first year of life.
Brain imbalance in adolescence
During puberty and until around the age of 25, the frontal cortex, among other things, continues to develop. Located just behind the forehead, this part of the cerebral cortex plays a role in planning, thinking and processing complex information, controlling the consequences of one’s behavior, and more.
During puberty, there can be some kind of imbalance in the brain as one area develops faster than another. For example, the frontal cortex grows quite slowly, while the amygdala, striatum and nucleus accumbens, an area deeper in the brain that is responsible for emotions, motivation and the feeling of reward, among other things, grow faster. As a result, in this phase of life we ​​react particularly emotionally and sensitively to rewards and take more risks.
Between the ages of 18 and 25, the brain will most likely continue to develop socially as it did in adolescence. However, we do not yet know whether there is a particularly sensitive or critical developmental phase in young adulthood. It is possible that during this phase we adapt better to different social situations: as friends, partners, colleagues and teammates, sometimes even as parents. It also seems that we are learning to differentiate better between what we ourselves want or think and what our environment expects of us. We are more considerate of others and know how to better control our own behavior.
And after 30 years? It is not the case that the brain is immediately broken down or that nothing can be learned anymore. The brain is still plastic. We see it, for example, in people who develop a tumor: some areas of the brain can take over the functions of others or work together. However, it is controversial to what extent new nerve cells develop and contribute to this over the course of life. However, after the age of 30, the brain begins to shrink slightly. After age 70, decline accelerates: connections are lost and memory declines.