//Stress
Many of us are familiar with the physical effects of stress, headaches, sweating, and lack of appetite, but did you know that stress can have an effect on your neurodevelopment? As mentioned earlier, neurogenesis refers to the birth of new neurons in the brain. Chronic stress has been linked to a decrease in neurogenesis in both children and adults. Children in particular are highly susceptible to a decrease in neurogenesis and other crucial neurodevelopmental changes. Stress may decrease neurogenesis, but, the opposite is also true. Environments that are low in stress and enriched in motor social, sensory, and cognitive factors are more likely to increase neurogenesis. This means that reducing stress in adolescence and teaching parents how to cultivate an enriched environment is incredibly important for neurodevelopmental changes.
//Pollution
In addition to its effects on prenatal development, pollutants, like air pollution, have a detrimental effect on children and adults. Different air pollution molecules enter the brain through the nasal passageways and cause inflammation with brain areas that they come into contact with. Typically, this is the olfactory bulb (an area related to processing scents) and the hippocampus (an area of the brain linked to learning and memory). So what does this mean for neurodevelopment? Studies have shown that exposure to a variety of different air pollutants during adolescence (and sometimes throughout adulthood) has been linked to issues with neurodevelopmental skills, attention, and behavior problems.
In addition to air pollution, water pollution has contributed to changing neurodevelopmental patterns. For example, the water crisis in Flint, Michigan has shown us how neurotoxins in drinking water can have an effect on development and behavior.
//Drugs and Alcohol
One of the most prevalent drugs, alcohol, has detrimental effects on neurodevelopmental, especially during adolescence. The adolescent brain grows and develops until about the age of 25. During this time, new neuron connections are formed, and preexisting connections are made stronger and more efficient through a process such as myelination (think of this process like wrapping something insulating around a wire to increase conduction). Drinking in early adolescence can cause decreases in gray matter, the part of the brain that deals with functions such as memory and emotion. It can also cause increases in white matter, the part of the brain that contains connections between neurons. While an increase in this area may be good in certain cases (and even normal during certain parts of development), an abnormal increase in white matter could be linked to certain diseases.
The second most prevalent drug used by teens and adolescents, marijuana, can also have an impact. The brain has a series of proteins known as receptors that can sense the presence of a molecule and then act accordingly depending on the molecule. In the brain, there are a series of receptors known as cannabinoid receptors, which sense and react to cannabis. Research has shown that the number of these receptors increases during adolescence and function heavily in neurodevelopmental. Thus, the use of cannabis under the age of 18 could lead to changes in this system and changes in downstream neurodevelopmental processes. This could manifest in adolescents as altered memory or attention span.