Although the brain stops growing in size by early adolescence, the teen years are all about fine-tuning how the brain works. The brain finishes developing and maturing in the age 60’s
The brain is constantly changing throughout life, and some changes occur as people age. The brain’s volume decreases overall, and the rate of shrinkage increases after age 60. The brain’s outer surface thins, and myelin shrinks, which can slow down processing and reduce cognitive function. However, some studies suggest that the brain remains sharp until age 60, and that people reach their peak emotional and mental potential between the ages of 60 and 80. 
Some things that can help support brain he
Staying active 
Eating healthy foods that are high in vitamins and fiber and low in animal fats 
Getting enough sleep, usually seven to nine hours per night 
Treating age-related sensory conditions like hearing or vision loss 
Reducing the risk of falls and other accidents that could lead to brain injuries 
Limiting alcohol use 
Quitting smoking and avoiding other nicotine products 
The most common issues are depression, dementia, and anxiety. Depression and dementia are the most common, affecting 5% to 7% of the population over 60. Anxiety follows as a close second, with the World Health Organization (WHO) reporting that it affects 3.8% of older adults.
The good news is, that unlike other parts of the body, our brains are built to change over our lifetime, meeting the challenges set by every life stage. While nobody can predict the exact ages of brain development, here’s a general guide to how the brain may change

When you lose your keys or forget a name, it may feel like your brain isn’t working as well as it used to. But new research dispels the belief that plasticity, the brain’s capacity to respond to change, diminishes in the adult and aging brain.”