A sensitive stage of development characterized by a biological onset (puberty) and a sociological offset (independence). 

Due to the biological and sociological differences in individuals and cultures, it is difficult to attribute chronological ages to adolescence, however, previous studies have suggested the following stages: early adolescence 11-13 years; middle adolescence 14-16 years; and late adolescence 17-22+ (even later in neurodivergent indviduals). 

• Decreased hippocampus (memory) volume

• Decreased PFC (Executive Function skills) volume 

• Increased amygdala volume (emotion) 

• Fewer strong, integrated neural pathways

• More prone to risk-taking, impulsivity, and reward. 

• Less able to process sensory input effectively, consider consequences, reason and plan ahead. 

• More sensitive to status and respect. 

• More reactive and susceptable to stress

Adolescent brains are in a sensitive phase of experience-expectant neuroplasticity in which cognitive processes such as reasoning, planning, and social cognition undergo significant development. The rate at which this takes place is second only to the first three years of life. 

This is a unique stage of synaptic reorganization: synapses are lost (synaptic pruning) and gained (synaptogenesis) dependent on experiences. 

Grey matter (neuronal cell bodies) are lost as the brain matures, resulting in fewer brain cells. However, white matter (myelinated axons) increases. Simply stated, the neurons that are not used are "pruned" and stronger, faster connections between the remaining neurons are developed through experience. 

The term "use it or lose it" applies to this stage of neural development. 

The intense phase of synaptic reorganization that occurs during early adolescence can result in a brief decline in processing and reasoning, and may partially explain the education dip that also occurs at this time.

While it is common for adults to lose hope for change after the age of 10 we now know that this is a mistake. Adolescent brains are in an essential "second window of opportunity" for development and uniquely sensitive to change. 

The graphs provided illustrate spikes in neural development in the frontal lobes (top) and the limbic system (bottom). The first spikes in development occur in the first 3 years of life, however, we now know that a second spike in development occurs in adolescence; but not at the same time.

The limbic system (behaviour and emotional control) spikes in middle adolescence, at an age when most Canadian adolescents are in grade 9 or 10. 

The frontol cortex (assoicated with executive function, cognition and social development) does not experience the same spike in growth until late adolescence, an age when most Canadian youth are graduated high school and beginning college. 

Adolescents are sensitive to their social environment. They go through a period of social reorientation in which attachment bonds with peers become more important than family. Part of becoming who we are begins with self-perceptions internalized from the perceptions of the views of others and how we see ourselves. This is known as the "looking glass self".  

Mental health disorders often have an onset in adolescence (Kessler et al. 2005) (Figure 2). The heightened vulnerability to psychiatric conditions during adolescence has been proposed to relate to genetically preprogrammed neural development at the same time as new stresses and challenges emerge in the environment (Andersen & Teicher 2008, Leussis & Andersen 2008).

To read more about Adolescence as a sensivie period for socicultural processing click here.

To learn more about the looking glass self, click here.

For more information about the adoloescent brain and mental health check out this article from the BBT Blog by clicking here